Early history.

In antiquity, two rival theories of the syllogism existed: Aristotelian syllogistic and Stoic syllogistic. Aristotle defines the syllogism as "a discourse in which certain (specific) things having been supposed, something different from the things supposed results of necessity because these things are so". Despite this very general definition, in "Prior Analytics" Aristotle limits himself to categorical syllogisms that consist of three categorical propositions. These include categorical modal syllogisms.  From the Middle Ages onwards, "categorical syllogism" and "syllogism" were usually used interchangeably. This article is concerned only with this traditional use. The syllogism was at the core of traditional deductive reasoning, where facts are determined by combining existing statements, in contrast to inductive reasoning where facts are determined by repeated observations.  Within academic contexts, the syllogism was superseded by first-order predicate logic following the work of Gottlob Frege, in particular his "Begriffsschrift" ("Concept Script") (1879), but syllogisms remain useful in some circumstances, and for general-audience introductions to logic.

Aristotle.

The use of syllogisms as a tool for understanding can be dated back to the logical reasoning discussions of Aristotle. Prior to the mid-twelfth century, medieval logicians were only familiar with a portion of Aristotle's works, including titles such as "Categories" and "On Interpretation", works that contributed heavily to the prevailing Old Logic, or "logica vetus". The onset of a New Logic, or "logica nova", arose alongside the reappearance of "Prior Analytics", the work in which Aristotle develops his theory of the syllogism.  "Prior Analytics", upon re-discovery, was instantly regarded by logicians as "a closed and complete body of doctrine", leaving very little for thinkers of the day to debate and re-organize. Aristotle's theory on the syllogism for "assertoric" sentences was considered especially remarkable, with only small systematic changes occurring to the concept over time. This theory of the syllogism would not enter the context of the more comprehensive logic of consequence until logic began to be reworked in general in the mid-fourteenth century by the likes of John Buridan.  Aristotle's "Prior Analytics" did not, however, incorporate such a comprehensive theory on the "modal syllogism"—a syllogism that has at least one modalized premise (that is, a premise containing the modal words 'necessarily', 'possibly', or 'contingently'). Aristotle's terminology in this aspect of his theory was deemed vague and in many cases unclear, even contradicting some of his statements from "On Interpretation". His original assertions on this specific component of the theory were left up to a considerable amount of conversation, resulting in a wide array of solutions put forth by commentators of the day. The system for modal syllogisms laid forth by Aristotle would ultimately be deemed unfit for practical use, and would be replaced by new distinctions and new theories altogether.

Medieval.

Boethius.

Boethius (c. 475 – 526) contributed an effort to make the ancient Aristotelian logic more accessible. While his Latin translation of "Prior Analytics" went primarily unused before the twelfth century, his textbooks on the categorical syllogism were central to expanding the syllogistic discussion. Boethius' logical legacy lay not in any addition he personally made to the field, but in his effective transmission of prior theories to later logicians, as well as his clear and primarily accurate presentations of Aristotle's contributions.

Peter Abelard.

Another of medieval logic's first contributors from the Latin West, Peter Abelard (1079–1142), gave his own thorough evaluation of the syllogism concept and accompanying theory in the "Dialectica" - a discussion of logic based on Boethius' commentaries and monographs. His perspective on syllogisms can be found in other works as well, such as "Logica Ingredientibus". With the help of Abelard's distinction between "de dicto" modal sentences and "de re" modal sentences, medieval logicians began to shape a more coherent concept of Aristotle's modal syllogism model.

John Buridan.

John Buridan (c. 1300 – 1361), whom some consider the foremost logician of the later Middle Ages, contributed two significant works: "Treatise on Consequence" and "Summulae de Dialectica", in which he discussed the concept of the syllogism, its components and distinctions, and ways to use the tool to expand its logical capability. For two hundred years after Buridan's discussions, little was said about syllogistic logic. Historians of logic have assessed that the primary changes in the post-Middle Age era were changes in respect to the public's awareness of original sources, a lessening of appreciation for the logic's sophistication and complexity, and an increase in logical ignorance—so that logicians of the early twentieth century came to view the whole system as ridiculous.

Modern history.

The Aristotelian syllogism dominated Western philosophical thought for many centuries. Syllogism itself is about how to get valid conclusion from assumptions (axioms) and not about verifying the assumptions. However, people over time focused on the logic part and forgot the importance of verifying the assumptions. In the 17th century, Francis Bacon emphasized that experimental verification of the assumptions must be carried out rigorously and cannot take syllogism itself as the best way to draw conclusions in nature. Bacon proposed a more inductive approach to the observation of nature, which involves experimentation and leads to discovering and building on axioms to create a more general conclusion. Yet, a full method to come to conclusions in nature is not the scope of logic or syllogism.  In the 19th century, modifications to syllogism were incorporated to deal with disjunctive ("A or B") and conditional ("if A then B") statements. Kant famously claimed, in "Logic" (1800), that logic was the one completed science, and that Aristotelian logic more or less included everything about logic there was to know. (This work is not necessarily representative of Kant's mature philosophy, which is often regarded as an innovation to logic itself.) Though there were alternative systems of logic, such as Avicennian logic or Indian logic elsewhere, Kant's opinion stood unchallenged in the West until 1879 when Frege published his "Begriffsschrift" ("Concept Script"). This introduced a calculus, a method of representing categorical statements (and statements that are not provided for in syllogism as well) by the use of quantifiers and variables.  A noteworthy exception is the logic developed in Bernard Bolzano's work "Wissenschaftslehre" ("Theory of Science", 1837), the principles of which were applied as a direct critique of Kant, in the posthumously published work "New Anti-Kant" (1850). The work of Bolzano had been largely overlooked until the late 20th century, among other reasons, due to the intellectual environment at the time in Bohemia, which was then part of the Austrian empire. In the last 20 years, Bolzano's work has resurfaced and become subject of both translation and contemporary study.  This led to the rapid development of sentential logic and first-order predicate logic, subsuming syllogistic reasoning, which was, therefore, after 2000 years, suddenly considered obsolete by many. The Aristotelian system is explicated in modern fora of academia primarily in introductory material and historical study.  One notable exception, to this modern relegation, is the continued application of Aristotelian logic by officials of the Congregation for the Doctrine of the Faith, and the Apostolic Tribunal of the Roman Rota, which still requires that any arguments crafted by Advocates be presented in syllogistic format.

Boole's acceptance of Aristotle.

George Boole's unwavering acceptance of Aristotle's logic is emphasized by the historian of logic John Corcoran in an accessible introduction to "Laws of Thought". Corcoran also wrote a point-by-point comparison of "Prior Analytics" and "Laws of Thought". According to Corcoran, Boole fully accepted and endorsed Aristotle's logic. Boole's goals were "to go under, over, and beyond" Aristotle's logic by: (1) providing it with mathematical foundations involving equations, (2) extending the class of problems it could treat, as solving equations was added to assessing validity, and (3) expanding the range of applications it could handle, such as expanding propositions of only two terms to those having arbitrarily many.  More specifically, Boole agreed with what Aristotle said; Boole's 'disagreements', if they might be called that, concern what Aristotle did not say. First, in the realm of foundations, Boole reduced Aristotle's four propositional forms to one form, the form of equations, which by itself was a revolutionary idea. Second, in the realm of logic's problems, Boole's addition of equation solving to logic—another revolutionary idea—involved Boole's doctrine that Aristotle's rules of inference (the "perfect syllogisms") must be supplemented by rules for equation solving. Third, in the realm of applications, Boole's system could handle multi-term propositions and arguments, whereas Aristotle could handle only two-termed subject-predicate propositions and arguments. For example, Aristotle's system could not deduce: "No quadrangle that is a square is a rectangle that is a rhombus" from "No square that is a quadrangle is a rhombus that is a rectangle" or from "No rhombus that is a rectangle is a square that is a quadrangle".

Basic structure.

A categorical syllogism consists of three parts:  Each part is a categorical proposition, and each categorical proposition contains two categorical terms. In Aristotle, each of the premises is in the form "All A are B," "Some A are B", "No A are B" or "Some A are not B", where "A" is one term and "B" is another. "All A are B," and "No A are B" are termed "universal" propositions; "Some A are B" and "Some A are not B" are termed "particular" propositions. More modern logicians allow some variation. Each of the premises has one term in common with the conclusion: in a major premise, this is the "major term" ("i.e.," the predicate of the conclusion); in a minor premise, this is the "minor term" ("i.e.," the subject of the conclusion). For example:  Each of the three distinct terms represents a category. In the above example, "humans", "mortal", and "Greeks". "Mortal" is the major term, "Greeks" the minor term. The premises also have one term in common with each other, which is known as the "middle term"; in this example, "humans". Both of the premises are universal, as is the conclusion.  Here, the major term is "die", the minor term is "men", and the middle term is "mortals". Again, both premises are universal, hence so is the conclusion.  A sorites is a form of argument in which a series of incomplete syllogisms is so arranged that the predicate of each premise forms the subject of the next until the subject of the first is joined with the predicate of the last in the conclusion. For example, one might argue that all lions are big cats, all big cats are predators, and all predators are carnivores. To conclude that therefore all lions are carnivores is to construct a sorites argument.

Types.

There are infinitely many possible syllogisms, but only 256 logically distinct types and only 24 valid types (enumerated below). A syllogism takes the form:  The premises and conclusion of a syllogism can be any of four types, which are labeled by letters as follows. The meaning of the letters is given by the table:  In "Analytics", Aristotle mostly uses the letters A, B, and C (the Greek letters alpha, beta, and gamma in the original) as term place holders, rather than giving concrete examples. It is traditional to use "is" rather than "are" as the copula, hence "All A is B" rather than "All As are Bs". It is traditional and convenient practice to use a, e, i, o as infix operators so the categorical statements can be written succinctly. The following table shows the longer form, the succinct shorthand, and equivalent expressions in predicate logic:  The convention here is that the letter S is the subject of the conclusion, P is the predicate of the conclusion, and M is the middle term. The major premise links M with P and the minor premise links M with S. However, the middle term can be either the subject or the predicate of each premise where it appears. The differing positions of the major, minor, and middle terms gives rise to another classification of syllogisms known as the "figure". Given that in each case the conclusion is S-P, the four figures are:  Putting it all together, there are 256 possible types of syllogisms (or 512 if the order of the major and minor premises is changed, though this makes no difference logically). Each premise and the conclusion can be of type A, E, I or O, and the syllogism can be any of the four figures. A syllogism can be described briefly by giving the letters for the premises and conclusion followed by the number for the figure. For example, the syllogism BARBARA below is AAA-1, or "A-A-A in the first figure".  The vast majority of the 256 possible forms of syllogism are invalid (the conclusion does not follow logically from the premises). The table below shows the valid forms. Even some of these are sometimes considered to commit the existential fallacy, meaning they are invalid if they mention an empty category. These controversial patterns are marked in "italics". All but four of the patterns in italics (felapton, darapti, fesapo and bamalip) are weakened moods, i.e. it is possible to draw a stronger conclusion from the premises.  The letters A, E, I, and O have been used since the medieval Schools to form mnemonic names for the forms as follows: 'Barbara' stands for AAA, 'Celarent' for EAE, etc.  Next to each premise and conclusion is a shorthand description of the sentence. So in AAI-3, the premise "All squares are rectangles" becomes "MaP"; the symbols mean that the first term ("square") is the middle term, the second term ("rectangle") is the predicate of the conclusion, and the relationship between the two terms is labeled "a" (All M are P).  The following table shows all syllogisms that are essentially different. The similar syllogisms share the same premises, just written in a different way. For example "Some pets are kittens" (SiM in Darii) could also be written as "Some kittens are pets" (MiS in Datisi).  In the Venn diagrams, the black areas indicate no elements, and the red areas indicate at least one element. In the predicate logic expressions, a horizontal bar over an expression means to negate ("logical not") the result of that expression.  It is also possible to use graphs (consisting of vertices and edges) to evaluate syllogisms.

Examples.

Celarent (EAE-1).

Similar: Cesare (EAE-2)

Darii (AII-1).

Similar: Datisi (AII-3)

Ferioque (EIO-1).

Similar: Festino (EIO-2), Ferison (EIO-3), Fresison (EIO-4)

"Celaront (EAO-1)".

Similar: "Cesaro (EAO-2)"

"Camestros (AEO-2)".

Similar: "Calemos (AEO-4)"

"Felapton (EAO-3)".

Similar: "Fesapo (EAO-4)"

Table of all syllogisms.

This table shows all 24 valid syllogisms, represented by Venn diagrams. Columns indicate similarity, and are grouped by combinations of premises. Borders correspond to conclusions. Those with an existential assumption are dashed.

Terms in syllogism.

We may, with Aristotle, distinguish singular terms, such as "Socrates", and general terms, such as "Greeks". Aristotle further distinguished (a) terms that could be the subject of predication, and (b) terms that could be predicated of others by the use of the copula ("is a"). (Such a predication is known as a distributive as opposed to non-distributive as in "Greeks are numerous". It is clear that Aristotle's syllogism works only for distributive predication for we cannot reason "All Greeks are animals, animals are numerous, therefore All Greeks are numerous".) In Aristotle's view singular terms were of type (a) and general terms of type (b). Thus "Men" can be predicated of "Socrates" but "Socrates" cannot be predicated of anything. Therefore, for a term to be interchangeable—to be either in the subject or predicate position of a proposition in a syllogism—the terms must be general terms, or "categorical terms" as they came to be called. Consequently, the propositions of a syllogism should be categorical propositions (both terms general) and syllogisms that employ only categorical terms came to be called "categorical syllogisms".  It is clear that nothing would prevent a singular term occurring in a syllogism—so long as it was always in the subject position—however, such a syllogism, even if valid, is not a categorical syllogism. An example is "Socrates is a man, all men are mortal, therefore Socrates is mortal." Intuitively this is as valid as "All Greeks are men, all men are mortal therefore all Greeks are mortals". To argue that its validity can be explained by the theory of syllogism would require that we show that "Socrates is a man" is the equivalent of a categorical proposition. It can be argued "Socrates is a man" is equivalent to "All that are identical to Socrates are men", so our non-categorical syllogism can be justified by use of the equivalence above and then citing BARBARA.

Existential import.

If a statement includes a term such that the statement is false if the term has no instances, then the statement is said to have existential import with respect to that term. It is ambiguous whether or not a universal statement of the form "All A is B" is to be considered as true, false, or even meaningless if there are no As. If it is considered as false in such cases, then the statement "All A is B" has existential import with respect to A.  It is claimed Aristotle's logic system does not cover cases where there are no instances. Aristotle's goal was to develop "a companion-logic for science. He relegates fictions, such as mermaids and unicorns, to the realms of poetry and literature. In his mind, they exist outside the ambit of science. This is why he leaves no room for such non-existent entities in his logic. This is a thoughtful choice, not an inadvertent omission. Technically, Aristotelian science is a search for definitions, where a definition is 'a phrase signifying a thing's essence.'... Because non-existent entities cannot be anything, they do not, in Aristotle's mind, possess an essence... This is why he leaves no place for fictional entities like goat-stags (or unicorns)."  However, many logic systems developed since "do" consider the case where there may be no instances.  However, medieval logicians were aware of the problem of existential import and maintained that negative propositions do not carry existential import, and that positive propositions with subjects that do not supposit are false.  The following problems arise:  For example, if it is accepted that AiB is false if there are no As and AaB entails AiB, then AiB has existential import with respect to A, and so does AaB. Further, if it is accepted that AiB entails BiA, then AiB and AaB have existential import with respect to B as well. Similarly, if AoB is false if there are no As, and AeB entails AoB, and AeB entails BeA (which in turn entails BoA) then both AeB and AoB have existential import with respect to both A and B. It follows immediately that all universal categorical statements have existential import with respect to both terms. If AaB and AeB is a fair representation of the use of statements in normal natural language of All A is B and No A is B respectively, then the following example consequences arise:  and so on.  If it is ruled that no universal statement has existential import then the square of opposition fails in several respects (e.g. AaB does not entail AiB) and a number of syllogisms are no longer valid (e.g. BaC,AaB->AiC).  These problems and paradoxes arise in both natural language statements and statements in syllogism form because of ambiguity, in particular ambiguity with respect to All. If "Fred claims all his books were Pulitzer Prize winners", is Fred claiming that he wrote any books? If not, then is what he claims true? Suppose Jane says none of her friends are poor; is that true if she has no friends?  The first-order predicate calculus avoids such ambiguity by using formulae that carry no existential import with respect to universal statements. Existential claims must be explicitly stated. Thus, natural language statements—of the forms "All A is B, No A is B", "Some A is B", and "Some A is not B"—can be represented in first order predicate calculus in which any existential import with respect to terms A and/or B is either explicit or not made at all. Consequently, the four forms "AaB, AeB, AiB", and "AoB" can be represented in first order predicate in every combination of existential import—so it can establish which construal, if any, preserves the square of opposition and the validity of the traditionally valid syllogism. Strawson claims such a construal is possible, but the results are such that, in his view, the answer to question (e) above is "no".  On the other hand, in modern mathematical logic, however, statements containing words "all", "some" and "no", can be stated in terms of set theory. If the set of all A's is labeled as s(A) and the set of all B's as s(B), then:  By definition, the empty set is a subset of all sets. From this it follows that, according to this mathematical convention, if there are no A's, then the statements "All A is B" and "No A is B" are always true whereas the statements "Some A is B" and "Some A is not B" are always false. This, however, implies that AaB does not entail AiB, and some of the syllogisms mentioned above are not valid when there are no A's.

Syllogistic fallacies.

People often make mistakes when reasoning syllogistically.  For instance, from the premises some A are B, some B are C, people tend to come to a definitive conclusion that therefore some A are C. However, this does not follow according to the rules of classical logic. For instance, while some cats (A) are black things (B), and some black things (B) are televisions (C), it does not follow from the parameters that some cats (A) are televisions (C). This is because in the structure of the syllogism invoked (i.e. III-1) the middle term is not distributed in either the major premise or in the minor premise, a pattern called the "fallacy of the undistributed middle".  Determining the validity of a syllogism involves determining the distribution of each term in each statement, meaning whether all members of that term are accounted for.  In simple syllogistic patterns, the fallacies of invalid patterns are:

A syllogism ( "syllogismos", "conclusion, inference") is a kind of logical argument that applies deductive reasoning to arrive at a conclusion based on two or more propositions that are asserted or assumed to be true.

直言三段论是所有前提都是直言命题的演绎推理。


History.

The term "Holstein" derives from Old Saxon "Holseta Land," ("Holz" and "Holt" mean wood in modern Standardised German and in literary English, respectively). Originally, it referred to the central of the three Saxon tribes north of the River Elbe: "Tedmarsgoi" (Dithmarschen), Holstein and "Sturmarii" (Stormarn). The area of the tribe of the Holsts was between the Stör River and Hamburg, and after Christianization, their main church was in Schenefeld. Saxon Holstein became a part of the Holy Roman Empire after Charlemagne's Saxon campaigns in the late eighth century. Since 811, the northern frontier of Holstein (and thus the Empire) was marked by the River Eider.  The term Schleswig comes from the city of Schleswig. The name derives from the Schlei inlet in the east and "vik" meaning inlet in Old Norse or settlement in Old Saxon, and linguistically identical (cognate) with the "-wick" or "-wich" element in place-names in Britain.  The Duchy of Schleswig or Southern Jutland was originally an integral part of Denmark, but was in medieval times established as a fief under the Kingdom of Denmark, with the same relation to the Danish Crown as for example Brandenburg or Bavaria vis-à-vis the Holy Roman Emperor. Around 1100, the Duke of Saxony gave Holstein, as it was his own country, to Count Adolf I of Schauenburg.

Duchies in the Danish realm.

Schleswig and Holstein have at different times belonged in part or completely to either Denmark or Germany, or have been virtually independent of both nations. The exception is that Schleswig had never been part of Germany until the Second Schleswig War in 1864. For many centuries, the King of Denmark was both a Danish Duke of Schleswig and a German Duke of Holstein. Essentially, Schleswig was either integrated into Denmark or was a Danish fief, and Holstein was a German fief and once a sovereign state long ago. Both were for several centuries ruled by the kings of Denmark. In 1721, all of Schleswig was united as a single duchy under the king of Denmark, and the great powers of Europe confirmed in an international treaty that all future kings of Denmark should automatically become dukes of Schleswig, and consequently Schleswig would always follow the same order of succession as the one chosen in the Kingdom of Denmark. In the church, following the reformation, German was used in the southern part of Schleswig and Danish in the northern part. This would later prove decisive for shaping national sentiments in the population, as well as after 1814 when mandatory school education was introduced. The administration of both duchies was conducted in German, despite the fact that they were governed from Copenhagen (from 1523 by the "German Chancellery" which was in 1806 renamed "Schleswig-Holstein Chancellery").

Schleswig-Holstein Question.

The German national awakening that followed the Napoleonic Wars gave rise to a strong popular movement in Holstein and Southern Schleswig for unification with a new Prussian-dominated Germany. This development was paralleled by an equally strong Danish national awakening in Denmark and Northern Schleswig. This movement called for the complete reintegration of Schleswig into the Kingdom of Denmark and demanded an end to discrimination against Danes in Schleswig. The ensuing conflict is sometimes called the Schleswig-Holstein Question. In 1848, King Frederick VII of Denmark declared that he would grant Denmark a liberal constitution and the immediate goal for the Danish national movement was to ensure that this constitution would give rights to all Danes, i.e. not only to those in the Kingdom of Denmark, but also to Danes (and Germans) living in Schleswig. Furthermore, they demanded protection for the Danish language in Schleswig (the dominant language in almost a quarter of Schleswig had changed from Danish to German since the beginning of the 19th century).  A liberal constitution for Holstein was not seriously considered in Copenhagen, since it was well known that the political élite of Holstein were more conservative than Copenhagen's. Representatives of German-minded Schleswig-Holsteiners demanded that Schleswig and Holstein be unified and allowed its own constitution and that Schleswig join Holstein as a member of the German Confederation. These demands were rejected by the Danish government in 1848, and the Germans of Holstein and southern Schleswig rebelled. This began the First Schleswig War (1848–51), which ended in a Danish victory at Idstedt.  In 1863, conflict broke out again when Frederick VII died without legitimate issue. According to the order of succession of Denmark and Schleswig, the crowns of both Denmark and Schleswig would pass to Duke Christian of Glücksburg, who became Christian IX. The transmission of the duchy of Holstein to the head of the (German-oriented) branch of the Danish royal family, the House of Augustenborg, was more controversial. The separation of the two duchies was challenged by the Augustenborg heir, who claimed, as in 1848, to be rightful heir of both Schleswig and Holstein. The promulgation of a common constitution for Denmark and Schleswig in November 1863 prompted Otto von Bismarck to intervene and Prussia and Austria declared war on Denmark. This was the Second War of Schleswig, which ended in Danish defeat. British attempts to mediate in the London Conference of 1864 failed, and Denmark lost Schleswig (Northern and Southern Schleswig), Holstein, and Lauenburg to Prussia and Austria.

Province of Prussia.

Contrary to the hopes of German Schleswig-Holsteiners, the area did not gain its independence, but was annexed as a province of Prussia in 1867. Also following the Austro-Prussian War in 1866, section five of the Peace of Prague stipulated that the people of Northern Schleswig would be consulted in a referendum on whether to remain under Prussian rule or return to Danish rule. This condition, however, was never fulfilled by Prussia. During the decades of Prussian rule within the German Empire, authorities attempted a Germanisation policy in the northern part of Schleswig, which remained predominantly Danish. The period also meant increased industrialisation of Schleswig-Holstein and the use of Kiel and Flensburg as important Imperial German Navy locations. The northernmost part and west coast of the province saw a wave of emigration to America, while some Danes of North Schleswig emigrated to Denmark.

Plebiscite in 1920.

Following the defeat of Germany in World War I, the Allied powers arranged a plebiscite in northern and central Schleswig. The plebiscite was conducted under the auspices of an international commission which designated two voting zones to cover the northern and south-central parts of Schleswig. Steps were taken to also create a third zone covering a southern area, but zone III was cancelled again and never voted, as the Danish government asked the commission not to expand the plebiscite to this area.  In zone I covering Northern Schleswig (10 February 1920), 75% voted for reunification with Denmark and 25% voted for Germany. In zone II covering central Schleswig (14 March 1920), the results were reversed; 80% voted for Germany and just 20% for Denmark. Only minor areas on the island of Föhr showed a Danish majority, and the rest of the Danish vote was primarily in the town of Flensburg.  On 15 June 1920, Northern Schleswig officially returned to Danish rule. The Danish/German border was the only one of the borders imposed on Germany by the Treaty of Versailles after World War I which was never challenged by Adolf Hitler.  In 1937, the Nazis passed the so-called Greater Hamburg Act ("Groß-Hamburg-Gesetz"), where the nearby Free and Hanseatic City of Hamburg was expanded, to encompass towns that had formerly belonged to the Prussian province of Schleswig-Holstein. To compensate Prussia for these losses (and partly because Hitler had a personal dislike for Lübeck), the 711-year-long independence of the Hansestadt Lübeck came to an end, and almost all its territory was incorporated into Schleswig-Holstein.

State of Federal Germany.

After World War II, the Prussian province Schleswig-Holstein came under British occupation. On 23 August 1946, the military government abolished the province and reconstituted it as a separate "Land".  Because of the forced migrations of Germans between 1944 and 1950, the population of Schleswig-Holstein increased by 33% (860,000 people). A pro-Danish political movement arose in Schleswig, with transfer of the area to Denmark as an ultimate goal. This was supported neither by the British occupation administration nor the Danish government. In 1955, the German and Danish governments issued the Bonn-Copenhagen Declarations confirming the rights of the ethnic minorities on both sides of the border. Conditions between the nationalities have since been stable and generally respectful.

Geography.

Schleswig-Holstein lies on the base of Jutland Peninsula between the North Sea and the Baltic Sea. Strictly speaking, "Schleswig" refers to the German Southern Schleswig ( or "Landesteil Schleswig", ), whereas Northern Schleswig is in Denmark (South Jutland County, Region of Southern Denmark). The state of Schleswig-Holstein further consists of Holstein, as well as Lauenburg and the formerly independent city of Lübeck.  Schleswig-Holstein borders Denmark (Southern Denmark) to the north, the North Sea to the west, the Baltic Sea to the east, and the German states of Lower Saxony, Hamburg, and Mecklenburg-Vorpommern to the south.  In the western part of the state, the lowlands have virtually no hills. The North Frisian Islands, as well as almost all of Schleswig-Holstein's North Sea coast, form the Schleswig-Holstein Wadden Sea National Park ("Nationalpark Schleswig-Holsteinisches Wattenmeer") which is the largest national park in Central Europe. Germany's only high-sea island, Heligoland, is situated in the North Sea.  The Baltic Sea coast in the east of Schleswig-Holstein is marked by bays, fjords, and cliff lines. Rolling hills (the highest elevation is the Bungsberg at ) and many lakes are found, especially in the eastern part of Holstein called the Holstein Switzerland and the former Duchy of Lauenburg ("Herzogtum Lauenburg"). Fehmarn is the only island off the eastern coast. The longest river besides the Elbe is the Eider; the most important waterway is the Kiel Canal which connects the North Sea and Baltic Sea.

Administration.

Schleswig-Holstein is divided into 11 "Kreise" (districts):  Furthermore, the four separate urban districts are:

Demographics.

Schleswig-Holstein has an aging population. Since 1972 there has been a decrease in the natural rate of population change. In 2016 the total fertility rate reached 1.61, highest value in 40 years (the average value being 1.4). In 2016 there were 25,420 births and 33,879 deaths, resulting in a natural decrease of -8,459.

Religion.

The region has been strongly Protestant since the time of the Protestant Reformation. It is proportionally the most Protestant of the sixteen modern states. In 2018, members of the Evangelical Church in Germany make up 44.6% of the population, while members of the Catholic Church comprise 6.1%. 49.3% of the population is not religious or adherent of other religions.

Foreigners.

Largest groups of foreign residents by 31 December 2018

Culture.

Schleswig-Holstein combines Danish and German aspects of culture. The castles and manors in the countryside are the best example for this tradition; some dishes like Rødgrød (, literal English "red grits" or "red groats") are also shared, as well as surnames such as Hansen.  The most important festivals are the Kiel Week, Schleswig-Holstein Musik Festival, an annual classic music festival all over the state, and the Lübeck Nordic Film Days, an annual film festival for movies from Scandinavian countries, held in Lübeck.  The annual Wacken Open Air festival is considered to be the largest heavy metal rock festival in the world.  The state's most important museum of cultural history is in Gottorf Castle in Schleswig.  The Wagnerian tenor Klaus Florian Vogt is from Schleswig - Holstein.

Symbols.

The coat of arms shows the symbols of the two duchies united in Schleswig-Holstein, i.e., the two lions for Schleswig and the leaf of a nettle for Holstein. Supposedly, Otto von Bismarck decreed that the two lions were to face the nettle because of the discomfort to their bottoms which would have resulted if the lions faced away from it.  The motto of Schleswig-Holstein is ""Up ewich ungedeelt"" (Middle Low German: "Forever undivided", modern High German: ""Auf ewig ungeteilt""). It goes back to the Vertrag von Ripen or Handfeste von Ripen (Danish: Ribe Håndfæstning) or Treaty of Ribe in 1460. Ripen (Ribe) is a historical small town at the North Sea coast in Northern Schleswig. See History of Schleswig-Holstein.  The anthem from 1844 is called "Wanke nicht, mein Vaterland" ("Don't falter, my fatherland"), but it is usually referred to with its first line ""Schleswig-Holstein meerumschlungen"" (i.e., "Schleswig-Holstein embraced by the seas") or "Schleswig-Holstein-Lied" (Schleswig-Holstein song).  The old city of Lübeck is a UNESCO World Heritage Site.

Languages.

The official language of Schleswig-Holstein is German. In addition, Low German, Danish and North Frisian are recognized minority languages.  Historically, Low German (in Holstein and Southern Schleswig), Danish (in Schleswig), and North Frisian (in Western Schleswig) were widely spoken in Schleswig-Holstein. During the language change in the 19th century some Danish and North Frisian dialects in Southern Schleswig were replaced by Standard German. Low German is still used in many parts of the state. Missingsch, a Low German dialect with heavy High German (Standard German) influence, is commonly spoken informally throughout the state, while a mixed language Petuh (mixture of High German and Danish) is used in and around Flensburg. Danish is used by the Danish minority in Southern Schleswig, and North Frisian is spoken by the North Frisians of the North Sea Coast and the Northern Frisian Islands in Southern Schleswig. The North Frisian dialect called Heligolandic ("Halunder") is spoken on the island of Heligoland.  As is the case throughout Germany, High German, introduced in the 16th century, has come to steadily replace local dialects for official purposes, and is today the predominant language of media, law and legislature. It is spoken by virtually all inhabitants in formal situations. Since the end of World War II and widespread adoption of TV, radio and other mass media, it has gradually come to supplant local dialects in urban areas as well.

Economy.

The Gross domestic product (GDP) of the state was 62.7 billion euros in 2018, accounting for 1.9% of German economic output. GDP per capita adjusted for purchasing power was 30,400 euros or 101% of the EU27 average in the same year. The GDP per employee was 95% of the EU average. The GDP per capita was the lowest of all states in West Germany.  Schleswig-Holstein is a leader in the country's growing renewable energy industry. In 2014, Schleswig-Holstein became the first German state to cover 100% of its electric power demand with renewable energy sources (chiefly wind, solar, and biomass).  Located between the North Sea and the Baltic Sea, Schleswig-Holstein is also a popular tourist destination in Germany. Its islands, beaches and cities attract millions of tourists every year. It has the second highest tourism intensity among the German states, after Mecklenburg-Vorpommern.  The unemployment rate stood at 5.0% in October 2018 and was marginally higher than the German average.

Education.

Compulsory education starts for children who are six years old on 30 June. All children attend a "Grundschule", which is Germany's equivalent to primary school, for the first 4 years and then move on to a secondary school. In Schleswig-Holstein there are "Gemeinschaftsschulen", which is a new type of comprehensive school. The regional schools, which go by the German name "Regionalschule" have been done away with as of 1 January 2014. The option of a Gymnasium is still available.  There are three universities in Kiel, Lübeck and Flensburg. Also, there are four public Universities of Applied Sciences in Flensburg, Heide, Kiel, and Lübeck. There is the Conservatory in Lübeck and the Muthesius Academy of Fine Arts in Kiel. There are also three private institutions of higher learning.

Politics.

Schleswig-Holstein has its own parliament and government which are located in the state capital Kiel. The Minister-President of Schleswig-Holstein is elected by the Landtag of Schleswig-Holstein.

Recent elections.

The most recent Schleswig-Holstein state elections were held on 7 May 2017. The governing parties consisting of the Social Democrats, the Green Party, and the South Schleswig Voters' Association lost their majority.

Schleswig-Holstein () is the northernmost of the 16 states of Germany, comprising most of the historical duchy of Holstein and the southern part of the former Duchy of Schleswig. Its capital city is Kiel; other notable cities are Lübeck and Flensburg.

石勒苏益格-荷尔斯泰因/什列斯威-荷斯坦(;;;)是德国16个州中最北面的一个州。这个州是在第二次世界大战后设立的,其州府为基尔。它面积15,761.4平方公里,是德国非城市州中第二小的(仅大于萨尔)。石勒苏益格-荷尔斯泰因北邻丹麦,南接德国的汉堡市、梅克伦堡-前波美拉尼亚和下萨克森三州。


History of Salyut space stations.

The programme was composed of civilian stations and military stations:  It was realized that the later civilian DOS stations could not only offer a cover story for the military Almaz programme, but could also be finished within one year and at least a year earlier than Almaz. The Salyut programme begun on 15 February 1970 on the condition that the crewed lunar program would not suffer. However, the engineers at OKB-1 perceived the L3 lunar lander effort as a dead-end and immediately switched to working on DOS. In the end it turned out that the Soviet N1 "Moon Shot" rocket never flew successfully, so OKB-1's decision to abandon the lunar program and derive a DOS space station from existing Soyuz subsystems and an Almaz/OPS hull proved to be right: The actual time from the DOS station's inception to the launch of the first DOS-based Salyut 1 space station took only 16 months; the world's first space station was launched by the Soviet Union, two years before the American Skylab or the first Almaz/OPS station flew.  Initially, the space stations were to be named "Zarya", the Russian word for 'Dawn'. However, as the launch of the first station in the programme was prepared, it was realised that this would conflict with the call sign "Zarya" of the flight control centre (TsUP) in Korolyov – therefore the name of the space stations was changed to "Salyut" shortly before launch of "Salyut 1". Another explanation given is that the name might have offended the Chinese, who purportedly were preparing a new rocket for launch, which they had already named "Dawn". The Salyut programme was managed by Kerim Kerimov, chairman of the state commission for Soyuz missions.  A total of nine space stations were launched in the Salyut programme, with six successfully hosting crews and setting some records along the way. However, it was the stations Salyut 6 and Salyut 7 that became the workhorses of the program. Out of the total of 1,697 days of occupancy that all Salyut crews achieved, Salyut 6 and 7 accounted for 1,499. While Skylab already featured a second docking port, these two Salyut stations became the first that actually utilized two docking ports: This made it possible for two Soyuz spacecraft to dock at the same time for crew exchange of the station and for Progress spacecraft to resupply the station, allowing for the first time a continuous ("permanent") occupation of space stations.  The heritage of the Salyut programme continued to live on in the first multi-module space station "Mir" with the Mir Core Module ("DOS-7"), that accumulated 4,592 days of occupancy, and in the International Space Station (ISS) with the "Zvezda" module ("DOS-8"), that accumulated 4,310 days of occupancy. Furthermore, the Functional Cargo Block space station modules were derived from the Almaz programme, with the "Zarya" ISS module being still in operation together with "Zvezda".

First generation – The first space stations.

Salyut 1 (DOS-1).

Salyut 1 (DOS-1) (; ) was launched on 19 April 1971. It was the first space station to orbit the Earth.  Its first crew launched in Soyuz 10 but were unable to board due to a failure in the docking mechanism; its second crew launched in Soyuz 11 and remained on board for 23 productive days. The world's first successful crewed flight to a space station was however overshadowed when the crew was killed before the re-entry of Soyuz 11 on 30 June 1971. A pressure equalisation valve in the descent module of the Soyuz opened prematurely when the three modules of the spacecraft separated, suffocating all three. Salyut 1 was moved to a higher orbit between July and August 1971 to ensure that it would not be destroyed prematurely through orbital decay. In the meantime, Soyuz capsules were being substantially re-designed to allow pressure suits to be worn during launch, docking maneuvers, and re-entry. However, Salyut 1 ran out of supplies before the Soyuz redesign effort was concluded, and it was decided to fire the engines for the last time on 11 October, to lower its orbit and ensure prompt destructive re-entry over the Pacific Ocean. After 175 days in space, the first real space station came to an end.

DOS-2.

DOS-2 was launched on 29 July 1972. It was similar in design to Salyut 1. The second stage of its Proton rocket failed; DOS-2 never reached orbit and crashed into the Pacific Ocean.

Salyut 2 (OPS-1, military).

Salyut 2 (OPS-1) (; ) was launched on 4 April 1973. The space station was, despite its "Salyut 2" designation, slated to be the first military space station, part of the highly classified Almaz military space station program – the Salyut designation was chosen to conceal its true nature. Although it launched successfully, within two days Salyut 2 began losing atmospheric pressure as its flight control system failed. The cause of the failure was likely shrapnel from the discarded and exploded Proton rocket upper stage that pierced the station. On 11 April 1973, seven days after launch, an unexplained accident caused both solar panels to be torn loose from the space station, cutting off all power. Salyut 2 re-entered on 28 May 1973.

Kosmos 557 (DOS-3).

The module DOS-3 was launched on 11 May 1973 – three days before the launch of Skylab – and was slated to become the next civilian space station with a Salyut designation. Due to errors in the flight control system while out of range from ground control, the station fired its orbital-correction engines until it consumed all of its fuel. Since the spacecraft was already in orbit and had been registered by Western radar, the Soviets disguised the launch as "Kosmos 557" – it was revealed to have been a Salyut station only much later. It re-entered Earth's atmosphere a week later, and burned up on re-entry.

Salyut 3 (OPS-2, military).

Salyut 3 (OPS-2) (; ) was launched on 25 June 1974. Like Salyut 2, it was another Almaz military space station, although unlike its predecessor, it was launched successfully. It was used to test a wide variety of reconnaissance sensors, returning a canister of film for analysis. On 24 January 1975, after the station had been ordered to deorbit, trials of an on-board autocannon (either a 23 mm Nudelman aircraft cannon or its 30 mm counterpart) were conducted with positive results at ranges from 3000 m to 500 m. Cosmonauts have confirmed that a target satellite was destroyed in the test. The next day, the station was ordered to deorbit. Only one of the two intended crews successfully boarded and crewed the station, brought by Soyuz 14; Soyuz 15 attempted to bring a second crew but failed to dock. Nevertheless, it was an overall success. The station's orbit decayed, and it re-entered the atmosphere on 24 January 1975.

Salyut 4 (DOS-4).

Salyut 4 (DOS-4) (; ) was launched on 26 December 1974. It was essentially a copy of DOS-3, but was a complete success. Two crews made stays aboard Salyut 4 (Soyuz 17 and Soyuz 18), including one of 63 days duration. An uncrewed Soyuz capsule (Soyuz 20) remained docked to the station for three months, proving the system's long-term durability. Salyut 4 was deorbited on 2 February 1977, and re-entered the Earth's atmosphere the next day.

Salyut 5 (OPS-3, military).

Salyut 5 (OPS-3) (; English translation "Salute 5") was launched on 22 June 1976. It was the third and last Almaz military space station. Its launch and subsequent mission were both completed successfully, with three crews launching and two (Soyuz 21 and Soyuz 24) successfully boarding the craft for lengthy stays (the second crew on Soyuz 23 was unable to dock and had to abort). Salyut 5 reentered on 8 August 1977.  Following Salyut 5, the Soviet military decided that with the advent of more sophisticated spy satellites, the tactical advantages were not worth the expense of the program and withdrew from the program. The focuses for the last two Salyut stations shifted towards civilian research and prestige for the Soviet Union.

Second generation – Long-duration inhabitation of space.

In 1977 another marked step forward was made with the second generation of Salyut stations. The aim was to continuously occupy a space station with long-duration expeditions, for the first time in spaceflight.  Although Salyut 6 and Salyut 7 resembled the previous Salyut stations in overall design, several revolutionary changes were made to the stations and program for the aim of continuous occupation. The new stations featured a longer design life and a second docking port at the aft of the stations – crew exchanges and station "handovers" were now made possible by docking two crewed Soyuz spacecraft at the same time. Furthermore, the uncrewed Progress resupply craft was created based on the crewed Soyuz, to resupply the crew and station with air, air regenerators, water, food, clothing, bedding, mail, propellants, pressurant, and other supplies. While the Progress docked to the station's second docking port, the crew's Soyuz spacecraft could remain docked to the station's first port. The Progress spacecraft even delivered hardware for updating onboard experiments and permitting repairs to the station, extending its life.

Salyut 6 (DOS-5).

Salyut 6 (DOS-5) (; ) was launched on 29 September 1977. Salyut 6 was crewed between 1977 and 1981 by 16 spacecraft, bringing five long-duration crews ("expeditions") and 11 short-term crews. The very first long-duration crew on Salyut 6 broke a record set onboard Skylab, staying 96 days in orbit. The short-term crews included foreign cosmonauts from the Interkosmos programme setting several firsts: the first citizen in space of a nation other than the United States or the Soviet Union, the first black and Hispanic person in space and the first Asian person in space. The longest flight onboard Salyut 6 lasted 185 days. The third long-duration Salyut 6 crew deployed a 10-meter radio-telescope antenna delivered by an uncrewed cargo spacecraft.  After Salyut 6 crewed operations were discontinued in 1981, a heavy uncrewed spacecraft called TKS, developed using hardware left from the canceled Almaz programme, was docked to the station as a hardware test. Some unconfirmed reports say that the station was functionally capable of even more missions, but combating the ever-increasing mold in living quarters was becoming impossible, and in practice caused the retirement decision. Salyut 6 was deorbited on 29 July 1982.

Salyut 7 (DOS-6).

Salyut 7 (DOS-6) (; ) was launched on 19 April 1982. DOS-6 was built as the backup vehicle for Salyut 6 with very similar equipment and capabilities, though several more advanced features were included. The station was in orbit for eight years and ten months, during which time it was crewed by ten spacecraft bringing six long-duration crews ("expeditions") and 4 short-term crews (including French and Indian cosmonauts in the Interkosmos programme).  On 12 February 1985, during an uncrewed period, contact with Salyut 7 was lost. The station had become crippled by electrical problems, with all systems shut down and the station beginning to drift. It was decided to put together a salvage mission, and on June 1985 the Soyuz T-13 mission, in what was in the words of author David S. F. Portree "one of the most impressive feats of in-space repairs in history," managed to bring the station online again.  The Soyuz T-15 mission was the last to visit Salyut 7 in 1986, ferrying equipment from Salyut 7 to the new "Mir" space station; This was so far the only ferry flight between two space stations.  Aside from the many experiments and observations made on Salyut 7, the station also tested the docking and use of large modules with an orbiting space station. These modules, called "Heavy Cosmos modules", helped engineers develop technology necessary to build "Mir".  Salyut 7 was deorbited on 7 February 1991.

Salyut's heritage – Modular space stations.

After the second generation, plans for the next generation of Salyut stations called for the cores DOS-7 and DOS-8 to allow, for the first time in spaceflight, the addition of several modules to a station core and to create a modular space station. For this, the DOS modules were to be equipped with a total of four docking ports: one docking port at the aft of the station as in the second generation Salyuts, and the replacement of the front docking port with a "docking sphere" containing a front port and starboard docking port.  While the station cores DOS-7 and DOS-8 were built and flown, they never received the Salyut designation. Instead, DOS-7 evolved into the Mir Core Module for the "Mir" space station that followed the Salyut programme, and DOS-8 was used as the "Zvezda" Service Module for the International Space Station (ISS) which followed "Mir".  The heritage from the Almaz program is present even today. While the last space station from the Almaz programme was flown as Salyut 5 in 1976, the development of the Almaz TKS spacecraft evolved into the Functional Cargo Block, which formed the basis for several "Mir" modules, the experimental Polyus orbital weapons platform and the "Zarya" module of the ISS.

Mir Core Module (DOS-7).

DOS-7 continued to be developed during Salyut 7, becoming the Mir Core Module of the "Mir" space station – the first modular space station, with crewed operations lasting from 1986 to 2000.  The station featured upgraded computers and solar arrays, and accommodations for two cosmonauts each having their own cabin. A total of six docking ports were available on the Mir Core Module, which were used for space station modules and visiting spacecraft – the docking sphere design had been upgraded from its initial Salyut design to contain a maximum of five docking ports (front, port, starboard, zenith and nadir). And finally, the modules for "Mir" were derived from the Functional Cargo Block design of the Almaz programme.  The name of the "Mir" space station –, literally "Peace" or "World" – was to signify the intentions of the Soviet Union to bring peace to the world. However, it was during the time of "Mir" that the Soviet Union was dissolved in 1991, ending what was begun with the 1917 October Revolution in Russia. This dissolution had started with the Soviet "perestroika and glasnost" ("restructuring and openness") reform campaigns by Soviet leader Mikhail Gorbachev in the 1980s, had reached a preliminary endpoint with the revolutions of 1989 and the end of the communist Eastern Bloc (Warsaw Pact and the CoMEcon), finally to reach the Soviet Union itself in 1991.  While the Russian Federation became the successor to much of the dissolved Soviet Union and was in a position to continue the Soviet space program with the Russian Federal Space Agency, it faced severe difficulties: imports and exports had steeply declined as the economic exchange with CoMEcon nations had crumbled away, leaving the industry of the former Soviet Union in shambles. Not only did the political change in eastern Europe signify an end of contributions to the space program by eastern European nations (such as the East German Carl Zeiss Jena), but parts of the Soviet space industry were located in the newly independent Ukraine, which was similarly cash-strapped as Russia and started to demand hard currency for its contributions.  It was during this time of transition and upheaval that the Shuttle–Mir Program was established between the Russian Federation and the United States in 1993. The former adversaries would now cooperate, with "Phase One" consisting of joint missions and flights of the US Space Shuttle to the Mir space station. It was a partnership with stark contrasts – Russia needed an inflow of hard currency to keep their space program aloft, while in the US it was seen as a chance to learn from the over 20 years of experience of Soviet space station operations. It was "Phase Two" of this Shuttle-Mir Program that would lead to the International Space Station.

Zvezda ISS Service Module (DOS-8).

DOS-8 evolved into the Mir-2 project, intended to replace "Mir". Finally, it became the International Space Station (ISS) "Zvezda" Service Module and formed the core of the early ISS together with the "Zarya" module (which was derived from Almaz Functional Cargo Block designs).

Data table.

For comparison, the modules that were derived from the Salyut/DOS development: All data for "Zvezda" (DOS-8).

The "Salyut" programme (,, meaning "salute" or "fireworks") was the first space station programme, undertaken by the Soviet Union. It involved a series of four crewed scientific research space stations and two crewed military reconnaissance space stations over a period of 15 years, from 1971 to 1986. Two other "Salyut" launches failed. In one respect, "Salyut" had the task of carrying out long-term research into the problems of living in space and a variety of astronomical, biological and Earth-resources experiments, and on the other hand the USSR used this civilian program as a cover for the highly secretive military "Almaz" stations, which flew under the "Salyut" designation. "Salyut" 1, the first station in the program, became the world's first crewed space station.

礼炮计划()是由前苏联计划的首个太空站计划,其中包括了于1971年至1986年这15年间发射的一系列九个的单模块(single-module)太空站。


Explanation.

Deuterium is a hydrogen isotope with a nucleus containing a neutron and a proton; the nucleus of a protium (normal hydrogen) atom consists of just a proton. The additional neutron makes a deuterium atom roughly twice as heavy as a protium atom.  A molecule of heavy water has two deuterium atoms in place of the two protium atoms of ordinary "light" water. The weight of a heavy water molecule, however, is not substantially different from that of a normal water molecule, because about 89% of the molecular weight of water comes from the single oxygen atom rather than the two hydrogen atoms. The colloquial term 'heavy water' refers to a highly enriched water mixture that contains mostly deuterium oxide, but also some hydrogen-deuterium oxide (HDO) and a smaller amount of ordinary hydrogen oxide. For instance, the heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction—meaning that 99.75% of the hydrogen atoms are of the heavy type. For comparison, ordinary water (the "ordinary water" used for a deuterium standard) contains only about

Other heavy forms of water.

Semiheavy water.

Semiheavy water, HDO, exists whenever there is water with light hydrogen (protium, ) and deuterium (D or ) in the mix. This is because hydrogen atoms (hydrogen-1 and deuterium) are rapidly exchanged between water molecules. Water containing 50% H and 50% D in its hydrogen actually

Heavy-oxygen water.

Water enriched in the heavier oxygen isotopes and is also commercially available, e.g., for use as a non-radioactive isotopic tracer. It is "heavy water" as it is denser than normal water ( is approximately as dense as, is

Tritiated water.

Tritiated water contains tritium (H) in place

Physical properties.

The physical properties of water and heavy water differ in several respects. Heavy water is less dissociated than light water at given temperature, and the true concentration of D ions is less than ions would be for a light water sample at the same temperature. The same is true of OD vs. ions. For heavy water Kw DO (25.0 °C) = 1.35 × 10, and [D] must equal [OD] for neutral water. Thus pKw DO = p[OD] + p[D] = 7.44 + 7.44 = 14.87 (25.0 °C), and the p[D] of neutral heavy water at 25.0 °C is 7.44.  The pD of heavy water is generally measured using pH electrodes giving a pH (apparent) value, or pHa, and at various temperatures a true acidic pD can be estimated from the directly pH meter measured pHa, such that pD+ = pHa (apparent reading from pH meter) + 0.41. The electrode correction for alkaline conditions is 0.456 for heavy water. The alkaline correction is then pD+ = pH(apparent reading from pH meter) + 0.456. These corrections are slightly different from the differences in

History.

The American scientist and Nobel laureate Harold Urey discovered the isotope deuterium in 1931 and was later able to concentrate it in water. Urey's mentor Gilbert Newton Lewis isolated the first sample of pure heavy water by electrolysis in 1933.

Effect on biological systems.

Different isotopes of chemical elements have slightly different chemical behaviors, but for most elements the differences are far too small to have a biological effect. In the case of hydrogen, larger differences in chemical properties among protium (light hydrogen), deuterium, and tritium occur, because chemical bond energy depends on the reduced mass of the nucleus–electron system; this is altered in heavy-hydrogen compounds (hydrogen-deuterium oxide is the most common species) more than for heavy-isotope substitution involving other chemical elements. The isotope effects are especially relevant in biological systems, which are very sensitive to even the smaller changes, due to isotopically-influenced properties of water when it acts as a solvent.  Heavy water is the only known chemical substance that affects the period of circadian oscillations, consistently increasing the length of each cycle. The effect has been demonstrated in unicellular organisms, green plants, isopods, insects, birds, mice, and hamsters. The mechanism is unknown.  To perform their tasks, enzymes rely on their finely-tuned networks of hydrogen bonds, both in the active center with their substrates, and outside the active center, to stabilize their tertiary structures. As a hydrogen bond with deuterium is slightly stronger than one involving ordinary hydrogen, in a highly deuterated environment, some normal reactions in cells are disrupted.  Particularly hard-hit by heavy water are the delicate assemblies of mitotic spindle formations necessary for cell division in eukaryotes. Plants stop growing and seeds do not germinate when given only heavy water, because heavy water stops eukaryotic cell division. The deuterium cell is larger and is a modification of the direction of division. The cell membrane also changes, and it reacts first to the impact of heavy water. In 1972 it was demonstrated that an increase in the percentage content of deuterium in water reduces plant growth. Research conducted on the growth of prokaryote microorganisms in artificial conditions of a heavy hydrogen environment showed that in this environment, all the hydrogen atoms of water could be replaced with deuterium. Experiments showed that bacteria can live in 98% heavy water. However, all concentrations over 50% were found to kill plants.

Effect on animals.

Experiments with mice, rats, and dogs have shown that a degree of 25% deuteration causes (sometimes irreversible) sterility, because neither gametes nor zygotes can develop. High concentrations of heavy water (90%) rapidly kill fish, tadpoles, flatworms, and "Drosophila". Mammals (for example, rats) given heavy water to drink die after a week, at a time when their body water approaches about 50% deuteration. The mode of death appears to be the same as that in cytotoxic poisoning (such as chemotherapy) or in acute radiation syndrome (though deuterium is not radioactive), and is due to deuterium's action in generally inhibiting cell division. It is more toxic to malignant cells than normal cells but the concentrations needed are too high for

Toxicity in humans.

Because it would take a very large amount of heavy water to replace 25% to 50% of a human being's body water (water being in turn 50–75% of body weight) with heavy water, accidental or intentional poisoning with heavy water is unlikely to the point of practical disregard. Poisoning would require that the victim ingest large amounts of heavy water without significant normal water intake for many days to produce any noticeable toxic effects.  Oral

Heavy water radiation contamination confusion.

Although many people associate heavy water primarily with its use in nuclear reactors, pure heavy water is not radioactive. Commercial-grade heavy water is slightly radioactive due to the presence of minute traces of natural tritium, but the same is true of ordinary water. Heavy water that has been used as a coolant in nuclear power plants contains substantially more tritium as a result of neutron bombardment of the deuterium in the heavy water (tritium is a health risk when ingested in large quantities).  In 1990, a disgruntled employee at the Point Lepreau Nuclear Generating Station in Canada obtained a sample (estimated as about a "half cup") of heavy water from the primary heat

Production.

On Earth, deuterated water, HDO, occurs naturally in normal water at a proportion of about 1 molecule in 3,200. This means that 1 in 6,400 hydrogen atoms is deuterium, which is 1 part in 3,200 by weight (hydrogen weight). The HDO may be separated from normal water by distillation or electrolysis and also by various chemical exchange processes, all of which exploit a kinetic isotope effect. With the partial enrichment also occurring in natural bodies of water under particular evaporation conditions. (For more information about the isotopic distribution of deuterium in water, see Vienna Standard Mean Ocean Water.) In theory, deuterium for heavy water could be created in a nuclear reactor, but separation from ordinary water is the cheapest bulk production process.  The difference in mass between the two hydrogen isotopes translates into a difference in the zero-point energy and thus into a slight difference in the speed of the reaction. Once HDO becomes a significant fraction of the water, heavy water becomes more prevalent as water molecules trade hydrogen atoms very frequently. Production of pure heavy water by distillation or electrolysis requires a large cascade of stills or electrolysis chambers and consumes large amounts of power, so the chemical methods are generally preferred.  The most cost-effective process for producing heavy water is the dual temperature exchange sulfide process (known as the Girdler sulfide process) developed in parallel by Karl-Hermann Geib and Jerome S. Spevack in 1943.  An alternative process, patented by Graham M. Keyser, uses lasers to selectively dissociate deuterated hydrofluorocarbons to form deuterium fluoride, which can then be separated by physical means. Although the energy consumption for this process is much less than for the Girdler sulfide process, this method is currently uneconomical due to the expense of procuring the necessary hydrofluorocarbons.  As noted, modern commercial heavy water is almost universally referred to, and sold as, deuterium oxide. It is most often sold in various grades of purity, from 98% enrichment to 99.75–99.98% deuterium enrichment (nuclear reactor grade) and occasionally even higher isotopic purity.

Argentina.

Argentina is the main producer of heavy water, using an ammonia/hydrogen exchange based plant supplied by Switzerland's Sulzer company. It is also a major exporter to Canada,

Soviet Union.

In October 1939, Soviet physicists Yakov Borisovich Zel'dovich and Yulii Borisovich Khariton concluded that heavy water and carbon were the only feasible moderators for a natural uranium reactor, and in August 1940, along with Georgy Flyorov, submitted a plan to the Russian Academy of Sciences calculating that 15 tons of heavy water were needed for a reactor. With the Soviet Union having no uranium mines at the time, young Academy workers were sent to Leningrad photographic shops to buy uranium nitrate, but the entire heavy water project was halted in 1941 when German forces invaded during Operation Barbarossa.  By 1943, Soviet scientists

United States.

During the Manhattan Project the United States constructed three heavy water production plants as part of the P-9 Project at Morgantown Ordnance Works, near Morgantown, West Virginia; at the Wabash River Ordnance Works, near Dana and Newport, Indiana; and at the Alabama Ordnance Works, near Childersburg and Sylacauga, Alabama. Heavy water was also acquired from the Cominco plant in Trail, British Columbia, Canada. The Chicago Pile-3 experimental reactor used heavy water as a moderator and went critical in 1944. The three domestic production plants were shut down in 1945 after producing

India.

India is one of the world's largest producers of heavy water through its Heavy Water Board and also exports to countries like Republic of Korea and the US. Development of heavy water process

Empire of Japan.

In the 1930s, it was suspected by the United States and Soviet Union that Austrian chemist Fritz Johann

Norway.

In 1934, Norsk Hydro built the first commercial heavy water plant at Vemork, Tinn, with a capacity of 12 tonnes per year. From 1940 and throughout World War II, the plant was under German control and the Allies decided to destroy the plant and its heavy water to inhibit German development of nuclear weapons. In late 1942, a planned raid called Operation Freshman by British airborne troops failed, both gliders crashing. The raiders were killed in the crash or subsequently executed by the Germans.  On the night of 27 February 1943 Operation Gunnerside succeeded. Norwegian commandos and local resistance managed to demolish small, but key parts of the electrolytic cells, dumping the accumulated heavy water down the factory drains.  On 16 November 1943, the Allied air forces dropped more than 400 bombs on the site. The Allied air raid prompted the Nazi government to move all available heavy water

Canada.

As part of its contribution to the Manhattan Project, Canada built and operated a to per month (design capacity) electrolytic heavy water plant at Trail, British Columbia, which started operation in 1943.  The Atomic Energy of Canada Limited (AECL) design of power reactor requires large quantities of heavy water to act as a neutron moderator and coolant. AECL ordered two heavy water plants, which were built and operated in Atlantic Canada at Glace Bay, Nova Scotia (by Deuterium of Canada Limited) and Port

Iran.

Since 1996 a plant for production of heavy water was being constructed at Khondab near Arak. On 26 August 2006, Iranian President Ahmadinejad inaugurated the expansion of the country's heavy-water plant. Iran has indicated that the heavy-water production facility will operate in tandem with a 40

Pakistan.

The 50 MW heavy water and natural uranium research reactor at Khushab, in Punjab province, is a central element of Pakistan's program

Other countries.

Romania used to produce heavy water at the now decommissioned Drobeta Girdler sulfide plant for domestic and export purposes.  France operated a small plant during the 1950s and 1960s.  Heavy water exists

Applications.

Nuclear magnetic resonance.

Deuterium oxide is used in nuclear magnetic resonance spectroscopy when using water as solvent if the nuclide of interest is hydrogen. This is because the signal from light-water (HO) solvent molecules interfere with observing the signal from the molecule of interest dissolved in it. Deuterium has a different magnetic moment and therefore does

Organic chemistry.

Deuterium oxide is often used as the source of deuterium for preparing specifically labelled isotopologues of organic compounds. For example, C-H bonds adjacent to ketonic carbonyl groups can be replaced by C-D bonds, using acid or base catalysis.

Infrared spectroscopy.

Deuterium oxide is often used instead of water when collecting FTIR spectra of proteins in solution. HO

Neutron moderator.

Heavy water is used in certain types of nuclear reactors, where it acts as a neutron moderator to slow down neutrons so that they are more likely to react with the fissile uranium-235 than with uranium-238, which captures neutrons without fissioning. The CANDU reactor uses this design. Light water also acts as a moderator, but because light water absorbs more neutrons than heavy water, reactors using light water for a reactor moderator must use enriched uranium rather than natural uranium, otherwise criticality is impossible. A significant fraction of outdated power reactors, such as the RBMK reactors in the USSR, were constructed using normal water for cooling but graphite as a moderator. However, the danger of graphite in power reactors (graphite fires in part led to the Chernobyl disaster) has led to the discontinuation of graphite in standard reactor designs.  Because they do not require uranium enrichment, heavy water reactors are more of a concern in regards to nuclear proliferation. The breeding and extraction of plutonium can be a relatively rapid and cheap route to building a

Neutrino detector.

The Sudbury Neutrino Observatory (SNO) in Sudbury, Ontario uses 1,000 tonnes of heavy water on loan from Atomic Energy of Canada Limited. The neutrino detector is underground in a mine, to shield it from muons produced by cosmic rays. SNO was built to answer the question of whether or not electron-type neutrinos produced by fusion in the Sun (the only type the Sun should be producing directly, according to theory) might be able to turn into other types of neutrinos on the way to Earth. SNO detects the Cherenkov radiation in the water from high-energy electrons produced from electron-type neutrinos as they undergo charged current (CC) interactions with neutrons in deuterium, turning them into protons and electrons (however, only the electrons are fast enough to produce Cherenkov radiation for detection).  SNO also detects neutrino electron

Metabolic rate testing in physiology and biology.

Heavy water is employed as part of a mixture with HO for

Tritium production.

Tritium is the active substance in self-powered lighting and controlled nuclear fusion, its other uses including autoradiography and radioactive labeling. It is also used in nuclear weapon design for boosted fission weapons and initiators. Some tritium is created in heavy water moderated reactors when deuterium captures a neutron. This reaction has a small cross-section (probability of a single neutron-capture event) and produces only small amounts of tritium, although enough to justify cleaning tritium from the moderator every few years to reduce the environmental risk of tritium escape.  Producing a lot of tritium in this

Heavy water (deuterium oxide, ', ') is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium ( or D, also known as "heavy hydrogen"), rather than the common hydrogen-1 isotope ( or H, also called protium) that makes up most of the hydrogen in normal water. The presence of deuterium gives the water different nuclear properties, and the increase of mass gives it slightly different physical and chemical properties when compared to normal water.

重水(或称<unk>代水,化学式DO或者HO)是水的一种,它的摩尔质量比一般水要重。普通的水(HO)是由两个只具有质子的氢原子和一个氧16原子所组成,但在重水分子内的两个氢同位素<unk>,比一般氢原子有各多一个中子,因此造成重水分子的质量比一般水要重。地球上水中的氢原子大约有6,400分之一是<unk>。