M. Ossan on some Bodies which strongly absorb Light. 159 



places alone are phosphorescent. This phosphorus, on that ac- 

 count, presents here and there points which shine with a pur- 

 plish red light. If it is exposed for a long time to an intense 

 heat, its light is discoloured, and ends with becoming entirely 

 white. 



3. PJwsphorus of Jrsenic.'^To obtain it, a kind of paste is 

 made of arseniate of barytes and gum-adragante, which is ex- 

 posed for half an hour to a red heat. Thus prepared, this phos- 

 phorus presents a greyish-yellow aspect, nearly the same as that 

 of Bologna phosphorus ; it diffuses a red light in the dark ; but if 

 it is heated longer than half an hour^ its colour becomes yellow ; 

 and under a longer heat, it ultimately becomes white. 



These three kinds of phosphorus are very luminous compa- 

 red with the following, which possess that property in a much 

 less degree. The dimmer phosphori are prepared in the same 

 manner as the phosphorus of antimony. The shells of oysters, 

 with mussive gold *, yield a phosphorus emitting a feeble bluish 

 light. With cinnabar there is obtained a phosphorus whose 

 light is yellow, nearly like that of Canton's phosphorus. With 

 white oxide of arsenic there is produced a bluish-yellow phos- 

 phorus; and with a very finely pulverised mixture of blend 

 and sulphur, a bluish phosphorus is obtained. The authors 

 obtained a very l)eautiful phosphorus, by treating Canton's phos- 

 phorus with realgar. 



All these compounds are kept in sealed vessels, or such as 

 are closed with a piece of bladder. They keep pretty long in 

 the open air ; for, at the end of three weeks, they had scarcely 

 lost any of their phosphorescence. It is only when the lime 

 falls into powder that their light is impaired. The phosphori of 

 antimony and realgar, however, lose the intensity of their colour, 

 when they are long exposed to the light. It is therefore a good 

 plan to keep them in blackened flasks. 



Phosphorus of arsenic is composed of equal parts of arsenic 

 and barytes, as Bologna phosphorus is of equal parts of barytes 

 and sulphur, and Canton's phosphorus of equal parts of lime and 

 sulphur. 



Cold favours the absorption of light, as heat favours its dis- 

 persion. Boiling water destroys the phosphoresscence. Phos- 

 • Mussive gold is bisulphuret of tin. 



