METALLIC StfLPHUR-ETS. 



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All thefe cinnabars differ with refped to their (hades of co- Thefe cinnabars 

 lour and finenefs ; fome are of a tinge approaching to purple, b l eau r t - ful pi g" y 

 violet, &c. That of fublimate combines with a great degree menu 

 of tenuity, a vivid fcarlet brilliancy. It is niuch iuperior to 

 the richeft vermilions, and it is to be wiflied that painters 

 might become acquainted with it. 



Others are pulverulent, of a dark or dull colour ; fuch are 

 thofe which the fulphuret of potafti yields ; they have neither 

 the luftre nor the tenuity of the others, for they are cry ftalline. 

 For the reft, all thefe cinnabars prefent no extraordinary ap* 

 pearances in fublimation ; by this procefs they lofe the bril- 

 liancy which they owed to their ftate of divifion. 



Tin, which has fo great an affinity with oxigen, takes how- Tin takes ful- 

 ever nothing elfe than fulphur from cinnabar ; if the latter SJUL ; r °b™t no" 

 contained alfo oxigen, it would take it from it with the fame oxigen : that 

 facility as it does the fulphur ; and the prefence of the one FjJJ prcfcnt. 

 would certainly be no impediment to the tin becoming charged 

 with the other : for if we heat a mixture of cinnabar and oxide 

 of tin at the maximum, we obtain mercury, fulphurated oxide 

 of tin, and fulphureous acid. This lad is here produced, as in 

 the cafe where fulphur is treated with the oxide of tin, by a 

 Teduclion which brings this oxide from the maximum to a mi- 



o 



nimum of oxidation, of which I do not yet know the numeri- 

 cal value, 



Sulphuret of Arfenic. 



This is alfo one of thofe which have long deceived me by The fulphuret* 



the analogy which its tranfparency and colour teems to indi- £**■" * on " 

 C>J r J tain no oxigen* 



cate. 



The arfenical acid and white oxide, treated with fulphur, 

 lofe their oxigen, yield fulphureous gas, and are reduced into 

 a fulphuret, which is tranfparent, vitreous, of a yellowilh red 

 colour, and capable of being raifed in diftillation. 



Pure arfenic, treated in the fame manner, yields the fame 

 kind of fulphuret, of perfect volatility, colour, and tranfpa- 

 rency. 



In whatever ways we may expofe thefe fulphurets to the 

 action of pulverifed charcoal, iron, tin, &c. they remain un- 

 alterable. Minute portions of fulphureous gas, and fulphurated 

 and arfenicated hidrogen, appear at firft in confequence of the 

 moifture, but nothing more. 



I 2 The 



