F-Centres in Metaphosphate Glass
A NUMBER of investigators1 have shown that glass on exposure to radioactive and X-radiation becomes coloured. Sheline, Sharp and Arner2 suggested that this may be due to F-centres similar to those produced in alkali halides when bombarded by X-rays and cathode rays. Yokota3 found that F-centres could be created in fused silica and α-quartz by X-irradiation. He further showed that alkali silicate and borate glasses become coloured on X-irradiation due to formation of F-centres4. Przibram5 showed that F-centres could also be created in borate glass by β- and γ-irradiation from radium.
V-centers in metaphosphate glass
Einige Autoren : ) h a b e n d a r a u f hingewiesel l , dab im t 8. Sol lnenf leckel lzyklus (f 944 bis 1954) die Zahl der ch romosph~rischel l E rup t ionen , die Pro tuberanzen t~ i t igke i t u n d die e r d m a g n e t i s c h e Akt iv i t i i t ger inger gewesen sind, als n a c h der H b h e der !Relat ivzahlen zu e rwar t en gewesen w/ire, u n d so is t die V e r m u t u n g e n t s t a n d e n 2), dab in d iesem Zyk lus die Fleckent / i t igkei t du rch die Re la t i vzah l mbgl icherweise t ibersch~tzt worden ist. Somi t is t eille N a c h p r f i f u n g der K o n s t a n z der R e l a t i v z a h l e n s k a l a m i t HiKe tier l lenerdings yon der Sternwar te Greenwich 3) ve r6 f fen t l i ch ten Lis te der Sollnenfleckenareale y o n In teresse . N a c h WALDMXlER 4) s ind die ] a h r e s m i t t e I R der t i iglich b e o b a c h t e t e n Sonnenf l eckenre l a t ivzah len dell J a h r e s m i t t e l n F der "c/~glichei1 F l~ ichensummen der Sollnenfleckell p ropor t iona l : F = t6,7R. U m eille i m Laufe der Zeit e twa e inge t re tene Ska lenXnderuug der Re la t ivzah len fes tzuste l len, habe ich den Z e i t r a u m yon t878 bis 1953, ftir den die mi t t l e r en Ciglichen F15.chensummen zur Ver f i igung s tehena) , in vier gleiche Abschn i t t e zu je 19 J a h r e n getei l t u n d fiir jedell dieser Abschn i t t e ge sonde r t den P r o p o r t i o n a l i t ~ t s f a k t o r a der Fo rme l F = a R d n r c h A u s g l e i c h u n g n a c h der Methode der k le ins ten Q u a d r a t e b e s t i m m t . I ch erhiel t folgende V~rerte m i t den angegebe l len m i t t l e r e n Feh le rn :
Die Bestrahlungsfarben des Steinsalzes in der Natur
Abstract A review is given of the present state of the interpretation of the yellow, violet and blue colours of natural rock salt as due to radiation. The yellow salt from Hall in the Tyrol and from Hallstatt is certainly coloured amicroscopically by radiation. The author has for a long time claimed the existence of an amicroscopic blue and violet colour in irradiated rock salt and this seems to be confirmed by the discovery of the R-centres ( Molnar, Seitz ). Many natural violet samples of rock salt are also optically empty and seemingly coloured by R-centres. According to a thorough investigation by L. Wieninger , the following groups of coloured rock salt can be distinguished : salt coloured only by amicroscopic centres, only by colloidal particles and by centres and colloidal particles simultaneously. As sources of radiation the following must be taken into consideration: the uranium-radium-contem of rock salt, its potassium-content and the extinct activity from radioactive thermal waters, according to O. Hahn , which can be deduced from the helium-content of rock salt. Also taking into consideration the fact that only a fraction of the available radiation is used for colouring, it can be shown that all these sources suffice for the explanation of the amicroscopic yellow and violet colour, the two last named also for that of the colloidal blue colour. That not all rock salt is coloured in Nature points to the necessity of sensibilizing and stabilizing impurities, which may also promote the formation of colloids.