Tobacco smoke filter
United States Patent Harendza-Harinxma et a1.  
 TOBACCO SMOKE FILTER Inventors; Alfred Joseph Harendza-Harinxma,  
 Lawrcnccville. N..I.  
 Assignees: Peter J. Catanese, Trenton; Saumel A. LaPaglia, Deane W. Merry. both of Pennington. all of, NJ. part interest to each Filed: Oct. 23, 1973 Appl. No.: 408.990  
 Related US. Application Data Division of Ser. No. 368.442. June 8. 1973. Pat. No. 3,842,071), which is a continuation-in-part of Scr. No. 210.043 Dec. 20. 1971, abandoned. which is a continuation of Scr. No. 69.760. Sept. 4, 1971). abandoned.  
 US. Cl 131/266; 131/2 Int. Cl A24b 15/02 Field of Search 260/212;  
 Apr. 8, 1975 1561 References Cited UNITED STATES PATENTS 3.351.071 11/1967 Belfort 131/265 3.353.543 11/1967 Sproull et al. 131/265 3.513.640 5/1970 Moliskey 131/267 FOREIGN PATENTS OR APPLICATIONS 1.489.730 7/1967 France 131/265 Primary E.\&#39;uminerMelvin D. Rein [57] ABSTRACT A fluid filter, especially useful for cigarettes and the like, comprises a complex product resulting from rcacting cellulose with an inorganic metal nitrate, such as manganese nitrate.  
 Other constituents, such as activated charcoal. tobacco. powdered pumice and thermoplastics may be added to the oxidized cellulose to modify the filtering action. The filter may also have application in the automobile industry.  
 7 Claims, 2 Drawing Figures PATENIEBAPRBIQH 3.875.949  
 FIG. 2  
  M/VE/VTUR A. J. HARENDZA-HAR/NXMA BY 3w. ATTORNEY TOBACCO SMOKE FILTER CROSS-REFERENCE TO RELATED APPLICATION This application comprises a division of application Ser. No. 368.442 filed June 8. 1973. now US. Pat. No. 3.842.070 which in turn is a continuation-in-part of copending application Ser. No. 210.043 filed Dec. 20. I971 which was a Rule 60 continuation of applications Ser. No. 69.760 filed Sept. 4. 1970 the two latter applications being abandoned.  
 BACKGROUND OF THE INVENTION l. Field of the invention Broadly speaking. this invention relates to filtration. More particularly. in a preferred embodiment. this invention relates to the filtration of noxious and offensive gases. particulate material and vapors, from the tobacco smoke.  
 2. Description of the Prior Art The rapid increase in the death rate due to lung cancer. emphysema. bronchitis and similar respiratory diseases has been traced to the growing amount of pollution in the air we breath. including the so-called personal air-pollution&#34; caused by cigarette smoking. The number of pollutants in the atmosphere are too numerous to list in detail but some of the principal components comprise carbon monoxide and lead from auto mobile exhausts; sulphur dioxide and soot from the burning of fossil fuel; and. in the case of cigarettes. nicotine. acrolein. phenol. tars. organic acids such as alcohol. acetic acid. ketones. esters. and other hydrocarbons and carbon dioxide. carbon monoxide and oxides of nitrogen.  
  Medical research has proved beyond doubt that many of the above-described pollutants are carcinogenic and some. such as acrolein (CH :CH.CHO). are ciliastatic. that is to say. they paralyze the cilia which line the trachea and bronchioles. Normally, these whip like appendages beat to and fro. in rhythmic fashion. and by this action carry foreign bodies up and out of the respiratory tract. thereby preventing foreign particulate matter from accumulating in the respiratory system. When the activity of the cilia is inhibited by acrolein or similar pollutants. harmful particulate material. including in the case of cigarette smoking any tar particles contained in the smoke. easily pass by the paralyzed cilia and collect in the lungs.  
  In view of the pressing health problem, vast research projects have been conducted. particularly in the cigarette industry, in an attempt to find a filter which will attenuate. or better still. eliminate most of these harmful elements. Unfortunately. the results to date have not been spectacular. While the smoker of a commercially manufactured filter cigarette is undoubtedly better off than if he were smoking a non-filtered cigarette. he nevertheless. runs a significant risk of contracting bronchitis or emphysema or other more dangerous illnesses.  
  Commercially available cigarette filters typically comprise a solid absorbent. such as activated charcoal or silica gel. sandwiched between a pair of cellulose acetate filter plugs. This type of filter removes from the tobacco smoke a proportion of the liquid or semi-liquid droplets passing through it. This is accomplished by a combination of diffusional. impactive. and direct collision of the droplets with the filter fibers. Upon collision. the droplets are retained on the fibers by the surface attraction between the extremely small particles and the relatively large fiber. Such fibrous filters are. however. not particularly effective for removing vaporized components from the smoke stream by the processes of physical and chemical adsorption. The smooth and non-porous nature of the commonly used fibrous filtering materials. while effective in capturing tobacco smoke droplets. does not present a sufficient surface area to effectively adsorb gaseous molecules. It has been calculated that an ordinary cellulose acetate cigarette filter plug has a surface area ranging from 1.000 to l0.000 square centimeters per gram of material. This affords insufficient surface area for effective adsorption of gaseous molemules. and has no significant selectivity. in some instances. where a vaporazied material is sufficiently soluble in the fibrous material so that its surface concentration is rapidly depleted. a significant removal can be achieved by the process of absorption. An example of such a material present in tobacco smoke is phenol. which has a pronounced solubility in cellulose acetate filtering material. Cellulose acetate filters allow both hydrogen cyanide and hydrogen sulfide to pass through in undesirably high concentration.  
  in attempts to improve the adsorptive properties of tobacco smoke filters. various treatments of ordinary filtering material and various new fibrous filtering materials have been proposed. Among the materials and treatments proposed. a number of well-known adsorbents such as activated charcoal. alumina. natural and synthetic clays and silica gel have been proposed as additives to tobacco smoke filters. These materials are classified as absorbents and are used in gas-stream treatment because they possess in common the characteristic that their specific surface area exceeds a million square centimeters per gram of material. A good grade of gas adsorbent quality activated carbon. for example. has a specific surface area in excess of 5 million square centimeters per gram. In general. the preferred method heretofore used of including these adsorbents in tobacco filters has been by dusting. spraying. tumbling. slurrying. or otherwise incorporating the finely-divided absorbent into the fibrous material which forms the filter or a part thereof.  
  Such adsorbent-containing tobacco smoke filters are only partially effective for several reasons. One is that the adsorbent is often rendered ineffective by the incorporation process and subsequent handling in the cigarette manufacturing and distribution process. in that water. plasticizing agents. glues. adhesives and volatile flavoring materials. in prolonged close contact with the finely-divided adsorbent. partially or completely utilize the adsorbent surface. thus decreasing its capacity to adsorb gaseous molecules from the smoke stream.  
  Another reason is that when adsorbent and fibrous filtering materials are intimately mixed. condensed droplets tend to be deposited in such a filter on or near an adsorbent particle. with the result that relatively nonvolatile smoke constitutes quickly permeate the adsorption and thus reduce its capacity for adsorption of gaseous molecules.  
  Further disadvantages of such known adsorbent filters are that the inclusion of considerable quantities of adsorbent in a tobacco smoke filter has both a marked effect upon the draw resistance of the smoking article. and upon the taste of the smoke stream. A powdered of finely divided adsorbent dispersed in a matrix of fbrous filtering elements impedes the flow of smoke through the filter and requires that the smoker apply additional suction to withdraw his normal amount of smoke. If enough adsorbent is included to remove considerable quantities of deleterious materials. the draw resistance is well above a desirable and comfortable levelv On the other hand. segregation of the adsorbent into a portion of the filter separated from the fibrous portion thereof. has pronounced deleterious effects on the taste of the smoke. When adsorbents such as charcoal. alumina. or silica gel are incorporated in a cigarette fil ter (segregated from the cellulose acetate filter) in sufficient quantities to considerably reduce the levels of gaseous materials. it is found that the taste ofthe smoke stream is far from pleasing to experienced smoke tasters. Although some irritating factors are reduced. the smoke is found to have an astringent. bitter. drying taste. Other mineral adsorbents have a similar overall effect. with minor modification in taste and aroma de pending on the particular adsorbent. The general result is that a pleasing smoke is obtained only when the amount of adsorbent is reduced to the point where it is well in minor proportion to the fibrous filtering agent.  
 When present at such diminished levels. it is insufficiently effective in removing undesirable smoke eonstitutents.  
  The problem then is to find a filter which does not rely on adsorption alone for its filtering action but which. nevertheless. is highly efficient in removing particulate. vapor and gaseous pollutants from the atmosphere. The filter should have application to the control of industrial pollution in general. and to the automobile industry in particular. and should also be of use in the cigarette industry. In this latter regard. the filter should be inexpensive. tasteless and should not add significantiy to the amount of draw required from the cigarette.  
 SUMMARY OF THE INVENTION As a solution to this problem an illustrative embodiment of the invention comprises a fluid filter which comprises cellulose which has been reacted with an inorganic nitrate of the formula Me(NO.-ilH&#39;H- O where Me represents a metal atom selected from the group consisting of Manganese. Nickel. Aluminum. Calcium. Iron. Sodium. Zinc and Copper and n is l. 2. 3 depending on the valence number ofthe corresponding metal.  
  Yet another embodiment of the invention comprises a method of manufacturing a filter material comprising the steps of forming an aqueous solution of an inorganic nitrate of the formula Me(NO;,)n&#39;H- O where Me represents a metal atom selected from the group consisting of Manganese. Nickel. Aluminum. Calcium. Iron. Sodium. Zinc and Copper and n equals l. 2 or 3. depending on the valence number of the corresponding metal; adding a cellulose-containing material in said aqueous solution; and heating said material to evaporate offthc aqueous solution remaining and decompose the nitrate.  
  The invention and its mode of operation will be more fully understood from the following detailed description. taken in conjunction with the drawings. in which:  
 DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric. partially cut-away view of an LII illustrative cigarette utilizing the flluid filter of this invention; and  
  FIG. 2 is a cross-sectional view of an illustrative to bacco pipe utilizing the fluid filter according to this invention.  
 DETAILED DESCRIPTION OF THE INVENTION The instant invention arose out of research which was directed towards finding an improved cigarette filter. It was quickly realized, however. that the filter material according to this invention may advantageously be used. by way of example and not of limitation, in the exhaust path of an internal combustion engine; in the flue or smoke-stack of an industrial plant; and at the input or output of an air-conditioning unit. or the like. When so used. the filter is highly efficient in removing unwanted gaseous and particulate pollutants.  
  The filter will be described in connection with its use as a cigarette filter; however. its use as a filtering medium for other applications should be borne in mind at all times.  
  Inorganic nitrates. may be defined as chemical compounds of the formula Mc(NO -,),,&#39;m H O. where Me represents a metal atom and it may be I. 2. or more. depending on the valence number of the metal. At ordinary temperatures nitrates are crystalline solids or solutions and may be white or colored. depending on the metal constitutent. As a group they are the most water soluble of all metal salts and are prepared by reaction of the desired metal. its oxide or its carbonate with nitric acid.  
  As will be seen from the specific examples to be given below. the filter material according to this invention is prepared by reacting cotton with a metallic nitrate to form a complex organic compound. The reaction is not fully understood.  
  The resulting complex organic compound may be mixed with other chemical constitutents to modify the filtering properties or it may be used alone. Again. the reaction between the filtering material and the pollutants is not fully understood. It is believed to be a true reaction (not merely ad adsorption) in which the pollutants are oxidized. This view is strengthened by the results of gas cheomatography experiments made on the fluid to be filtered before and after filtration. These experiments indicate an increase in the percentage of oxygen which could not occur in an adsorption process alone.  
  The inability to properly characterize the filtering material and the manner in which it operates is. of course. no bar to patentability nor to the successful use of the material in filters of various types.  
 EXAMPLE I 4.5 grams of cotton was added in lOO mil of a 50 percent by weight Manganese Nitrate in a porcelain dish and heated on a hotplate to a temperature of approximately 250C for approximately 3 hours. or until all the remaining Manganese Nitrate solution had evaporated. and the remaining nitrate decomposed. During the decomposition of nitrate. N0 gas was observed.  
  The material remaining was then ground into a fine black powder and mixed with water to form a suspension.  
  Fresh cotton was then soaked in the suspension and dried to form the filtering material.  
 EXAMPLE II In the process disclosed in Example I. rather than form a suspension of the black powder in water. the black powder is ground with fresh cotton to impregnate the cotton with the powdered material and form the filter. For use as a cigarette filter. from 60 to 350. preferably I50 mg. of the black powder is ground into about 60 mg. of cotton.  
 EXAMPLE lll Seventy mi] of 50 percent Manganese Nitrate (MnNO;,) &#39;6H O solution was mixed with 30 mil of an 85 percent solution by weight of Phosphoric Acid (HH t).  
  Next. 4.5 mg. of cotton was added to the mixture and left to soak for approximately l2 hours. or until the cotton began to decompose.  
  The resulting gel was placed in a porcelain dish and heated on a hotplate at a temperature of approximately 250C until the remaining liquids were evaporated and the nitrate decomposed. A yellowish-brown powder was obtained which may be used as the filtering agent.  
 EXAMPLE IV A filter was formed by mixing the following ingredients:  
 43.4 grams of the black powder of Example I 2.] grams pure shredded tobacco 34.4 grams of the yellow-brown powder of Example ll L8 grams charcoal [7.2 grams 120 mesh Pumice l.l grams granular thermoplastic powder The charcoal was included to remove any odor which may be added to the taste of the cigarette smoke by the other ingredients. The 120 mesh. partially ground. pumice is an inert material added to increase the porosity of the filter. The thermoplastic material was obtained for convenience. from commercially available HUNTbrand xerographic toner. but obviously other thermoplastic powders could also be used.  
 EXAMPLE V I2 ml. of 50% Manganese Nitrate lMn(NO;,)- &#39;6H Ol was mixed with 0.5 g charcoal and 0.5 g cotton and left for approximately l2 hours. or until the cotton began to dissolve. Next. the mixture was placed in a porcelain dish and heated on a hotplate at a temperature of approximately 250C until all the remaining liquid had been evaporated and the Nitrate decomposed.  
  The material remaining was black in color and when ground yielded a fine black powder. similar in appearance to that obtained in Example I.  
 EXAMPLE VI Zinc Nitrate [Zn(NO;,)-,&#39;6H O] was dissolved in distilled water to form a 507: solution by weight.  
  l0 ml ofthe above solution was mixed with 0.5 grams of cotton and permitted to stand for approximately 12 hours. or until the cotton began to decompose. Next. the mixture was placed in a porcelain dish and heated on a hotplate until the remaining solution was evaporated and Nitrate decomposed.  
  A grayish-white powder was obtained and used as the filter material.  
 EXAMPLE Vll I25 grams of Aluminum Nitrate [Al(NO );,&#39;9H O] and 7.5 grams of cotton was dissolved in a mixture of I50 ml. of H 0 and 16 ml. of concentrated Nitric Acid (HNO3) strength.  
  After about 30 minutes. the partially dissolved cotton was removed and placed in a porcelain dish. The dish was then heated on :1 250C hotplate until the remaining liquid had evaporated and Nitrate decomposed. The resulting solid material was ground to a fine white powder to provide the filter material.  
 EXAMPLE Vlll The mixture set forth in Example V&#34; was permitted to remain in solution for approximately 90 minutes. or until the cotton had totally dissolved.  
  The mixture was then evaporated on a hotplate. as in Example Vll. During evaporation. N0 gas was ob served being driven off. Again. the residue was ground to a fine white powder.  
 EXAMPLE lX Ferric Nitrate [Fe(NO;,); 9H O] was dissolved in distilled water to form a 50 percent solution by weight.  
  Five grams of cotton were then dissolved in I00 mil of concentrated 70 percent Nitric Acid (HNQ-g). Then. l0 mil of the Fe(NO; );,-9H O solution were mixed with l5 mil of the HNO cotton mixture and an additional l.75 grams of cotton added. The resultant material was permitted to stand for approximately 12 hours. or until the cotton was completely dissolved. Next. the remaining material was heated on a hotplate at 250C until all remaining liquid was evaporated and Nitrate decomposed.  
  A brownish-yellow powder was obtained which was used as a filter material.  
 EXAMPLE X One hundred grams of Calcium Nitrate ICa{NO r4- H O] was dissolved in I00 mil of H 0.  
  2.25 grams of cotton was then added to 50 mil of the above solution and 3 mi] of concentrated 70 percent Nitric Acid. The cotton was dissolved in the solution.  
  An additional 2.5 grams of cotton was then added in the solution. Excess HNO,, and Ca(NO; were then removed by a water rinse.  
  The cotton was then permitted to dry and after a flash fire burned to dark grey powder which formed the filter material.  
 EXAMPLE XI One hundred grams of Copper Nitrate lCu(NO )-,&#39;3- H O] was dissolved in l00 mil H O. Next. the L grams of cotton were placed in 20 mil of the above solution and permitted to stand for 12 hours.  
  The resulting mass was placed in a porcelain dish and heated on a hotplate at 250C. The mixture burned fiercely leaving a dark brown residue which was then ground into a fine powder.  
 EXAMPLE Xll Ten grams of Sodium Nitrate (NaN l were dissolved in 20 mils of H 0.  
  Then 0.25 grams of cotton were dipped in the above solution for 30 minutes and then placed in a crucible and dried.  
  Next. to remove any excess NaNO remaining. the cotton was subjected to a water rinse and another dry ing cycle. Finally, approximately three drops of the Nitric Acid solution described in Example IX was added ton. crepe paper. etc. and the filter material may comprise any of the compositions listed in Examples I through Xll.  
 FIG. 2 illustrates how the filter may be used in a dist the Cottoh- After approximately 30 mthutesthe 6131&#39; posable cartridge for a pipe. or cigarette. or cigar cible was placed in a furnace at 400C and heated until h ld remaining hquld h h evtlpmllted unfit the As shown. pipe 20 comprises a bowl 2] and a stem trate decomposed. yielding the filter material which 22 h dbl md thereto was gtttytsh btowh 4 A filter cartridge 23 is positioned within the bore of The filter material which was produced in Examples Stem 22 d Comprises a porous a er cylinder filled and he YTIIXL&#34;;I with with filter material as described in Examples l Xll. watetto totth sttspehstoh and t or other slmlhlr The filter arrangements for use with automobiles, air matenah ppe 1h the Suspehslhh 10 form the that conditioners, etc. are entirely analogous and are not filter. as descri d n i P l and shown in detail. It will. of course. be necessary to utilize Attethatlvetyi tohiltfeo- Charcoal: p ep different kinds and quantities of inert filler material. may be used to dltute the fittetlhg matenflt as but this is well within the scope of a person skilled in scnbed in Exampie IV. h n  
  Actuuttye ttttet rhtttettat pmdtlced according to The amount of filtration attainable with the filter ma- Ptocesses of thts tm&#39;ehtloh $0 efficte&#39;ht that some &#39;8 terial according to this invention is truly spectacular. arette smokers may find its tar and nicotine removing Table behw li h rcsutts f tnhnrntory |y abilities ObJECtlOnllblC. In that event. the filter material i on cofnmgrcially il bl cigarettes, both filtered be dthttett y the addttloh 0f more and more and unfiltered. as well as the same commercially availmtltetlttts- Such as tobacco or P Of course this able unfiltered cigarette in combination with several increases the amount of harmful material in the smoke. diff types f the n according to this invention TABLE A Concentration it Volume/Volume Methane Carbon Carbon Tars mg/ A: Nitric Mon- Di- Cigarette Cigarette Puffs Oxygen Oxide oxide oxide Commercial Cigarette A l3.2 3 l-Ul .35 3.3 5.8 (No Filter) 0 12.0 .39 3.2 9.7 Commercial Cigarette B l7.) 3 14.0 .52 2.7 8.3 [No Filter) (1 l2.(l .49 3.2 l 1.2 Commercial Cigarette A 0.4 3 lti.0 .25 [.2 4.6 (Short Filter (1 H1) .38 L8 6.7 No. l) Commercial Cigarette A 3.5 3 14.0 .52 3.5 8.8 (Short Filter 6 l4.0 .49 3.4 9.3 No. 2|M Commercial Cigarette A 4.4 3 l-H) .34 3.2 8.6 [Long Filter 6 I20 .ol 5.4 l2.3 No. 4] Commcrcial Cigarette A 3.3 3 I .38 2.5 8.4 (Long Filter t I20 .62 3.8 10.4 No. 4-2) Commercial Cigarette D 12.4 3 l4.0 .45 2.6 8.3 lFiltered) 6 I20 .57 4.3 l0.2  
 Zsec.)  
  Unlike conventional adsorption-type filters. which are generally spent after one cigarette. it is an impor tant aspect of this invention that the filter material remains active and may be used for two. three or more cigarettes. It is ideally suited. therefore. for use as a disposable filter element for pipes. cigar holders. cigarette holders. etc.  
  FIG. 1 illustrates a typical use of the filter material according to this invention.  
  As shown. cigarette 10 comprises shredded tobacco ll rolled with a paper cylinder 12. A filter 13 is posi tioned at an extreme end of the cigarette and comprises first and second filter retaining means 15 and 16 between which the filter material proper 17 is sandwiched. The filter retaining means may comprise cot- The sampling and analyses were performed as fol lows:  
  The cigarette was inserted into a special Gelman holder. containing a tared Cambridge Filter. The holder was attached to a vacuum system drawing one 35 cc puff in 2 seconds every minute. Samples of the third and sixth puff were removed in glass syringes. and injected onto chromatographic columns for analysis.  
  The Oxygen. Methane Nitric Oxide. and Carbon Monoxide analysis was achieved on a molecular sieve column maintained at C. Separation of other constituents, except Carbon Dioxide. was achieved on a 12 ft one-fourth in. Porapak 0 Column 2 in. Porapak R Column programmed from 90C to 220C at 30C/minute. The carbon dioxide was separated on a 6 ft X onefourth in. silica gel column maintained at 90C.  
  The tar values were obtained by weighing the Cambridge Filter before and after smoking the cigarette.  
  Table 8. below. gives the result ofa chromatographic analysis on the smoke of the same cigarettes tested in Table A.  
 TABLE B PEAK HEIGHT (DIVISIONS) Commercial Commercial Commercial Commercial Reten- Commercial Commercial Cig. A Cig. A Cig. A Cig. A Commercial lion Cig. A No. l Short No. 2 Short No. 4 Long No. 4-2 Long (&#39;ig. D Time Constituents Drag No Filter No Filter Filter Filler Filter Filter Filtered 2.0 Unidentified 3rd I280 I600 315 I570 I I80 I200 I380 6th I600 I600 I I70 I540 I600 I600 I600 4 4 Unidentified 3rd I40 208 I I80 I56 I72 220 6th 180 252 I28 I88 2l2 220 272 5.6 Unidentified 3rd 2 I2 262 I44 240 I96 I92 400 bth 240 400 I60 232 263 256 400 9.5 3rd I76 2 I 6 I20 200 I60 I64 204 Hydro en 6th I96 248 I44 I92 220 220 236 Cyanit e 9.8 3rd I44 I76 I00 I60 124 I24 I64 6th I56 I88 I32 I68 I64 I76 I92 I00 Unidentified 3rd 48 b4 32 48 48 56 44 6th 56 52 32 48 (18 54 52 I Formaldehyde 3rd I2 lb 4 8 4 ti 8 (1th I2 20 8 I2 I2 12 24 I l. Acetaldchyde rd I70 I92 I00 I94 I I90 I62 6th I (14 I70 I04 I72 200 200 I 82 I2.b Unidentified 3rd 68 84 48 7X 60 72 74 6th 72 90 56 72 82 90 82 I 3.0 Unidentified 3rd 50 56 34 56 46 56 6th (i2 40 50 5h 58 42 I40 Unidentified 3rd lb I8 8 I8 6 22 I0 6th In 20 I0 20 30 24 I4 I50 Acrolein 3rd 84 92 52 98 (10 I04 82 6th 78 94 6O 80 I I0 98 84 l5.8 Unidentified 3rd 2 2 l 2 I 4 2 mh 2 2 i 2 2 4 2 I Unidentified 3rd I02 98 74- I I4 66 I I0 6th 82 6o 82 98 I22 lib 20.4 Unidentified 3rd I8 I2 I0 20 8 20 I2 6th I0 I2 I0 I2 22 I6 I2 It will be noted that when applicants filter is used. the tar content drops from a high of I79 mg. to a dramatic low of 0.4 mg. Similarly, the oxygen content of the smoke increases from a concentration of 14.0% to l6.0/i; carbon dioxide drops from a high of 3.3% to a low of 1.27r; carbon dioxide drops from a high of 5.8% to a low of4.67r and on subsequent puffs when the unfiltered cigarette rises to I 1.2%. the filtered cigarettes according to this invention only rises to 6.7%. Methane and Nitric Oxide also drop from a high of 0.52% to 0.25%  
  Acralein. an important carcinogen. drops from a high of 92 to a low of 52 while hydrogen cynanide drops from a high of I76 to a low of I20. Formaldehyde similarly drops from I4 to l2.  
  In these analytic tests. the filters used were similar to the Manganese Nitrate filters described in Examples I through III. Similar. or better. results have been obtained with the filter material described in Examples IV through XII.  
  The various times. temperatures. concentrations and masses in the Examples are not unduly critical and wide variation is possible. Similarly. the percentages of the various constitutents in the filters are not critical and wide variation is again possible.  
  One skilled in the art may make various changes and substitutions in the processes disclosed. without departing from the spirit and scope of the invention.  
 What is claimed is:  
  I. In combination with a smoker&#39;s article of the type wherein a quantity of tobacco is ignited and smoke is drann therefrom by a smoker. the improvement which comprises a filter means interposed between the acting cellulose with an inorganic nitrate ofthe formula Me(NO;,)n where Me represents a metal atom selected from the group consisting of Manga nese. Nickel. Aluminum. Calcium. Iron. Sodium, Zinc and Copper and n is a number corresponding to the valence number of the metal atom; and  
 b. from at least 15 to approximately 90 percent by weight ofinert granular material to increase the p0 rosity of said plug.  
  2. The filter according to claim I wherein said inert granular material comprises Pumice.  
  3. The improvement according to claim wherein said smokers article is a cigarette comprising a tobacco section and a filter section. said filter section including said plug and at least one filter retaining element, said plug being interposed between said tobacco section and said at least one filter-retaining means and being disposed adjacent to said tobacco section.  
  4. The improvement according to claim 1 wherein said plug further includes a minor part by weight of ac tivated charcoal.  
  5. The improvement according to claim 1 wherein said plug further includes a minor part by weight of a granular thermoplastic powder.  
  6. The improvement according to claim I wherein said smokers article is a pipe having a tobacco-burning bowl and a stern. said plug being positioned in said stern in the path ofthe smoke which is drawn from said bowl.  
  7. The improvement according to claim I wherein said smokers article is a cigar; the combination further including a cigar-holder for receiving an end of the cigar and including said filter-plug.