Analyfis bj the Spinel Ruty. 43 



iJiflblvech atleaft for the greater part, by additional quantities 

 of the acid. I warmed the iblution by a gentle heat, and 

 having filtered it, there remained on the paper three parts of 

 a rofe-coloured powder, which was ruby, not deeompofedi 

 This I placed apart, that I might operate only on that por- 

 tion which had been attacked. 



V. The muriatic folution above mentioned having been 

 evaporated to drynefs by a gentle heat, I poured upon the 

 refiduum a large quantity of diftilled water : almoft the 

 whole of it was diflblved. There remained only five parts of 

 a grey powder, which melted with borax, to which it com- 

 municated a green colour. 



VI. I fubjefted thefe five parts to different tefts, which 

 fhewed, that they were filiceous earth mixed with a little alu- 

 mine, and coloured by a matter, of which I {hall fpeak here- 

 after*. 



VII. I precipitated the muriatic folution of Exp. V. with 

 carbonat of ammonia. When I judged that I had added a 

 fufficient quantity, I boiled the mixture for a quarter of an 

 hour, in order to expel the carbonic acid, and favour the pre- 

 cipitation of the lime or rnagnefia, if there were any of thefe 

 in it. By thefe means I obtained an abundant white preci- 

 pitate, which I boiled with a folution of cauftic potafli. The 

 greater part of this precipitate was diflblved. There remained 

 only iql parts of a brown fubftance inclining to violet, but 

 which turned to a yellowifh-green colour/ by drying in a 

 gentle heat. 



* In another analyfis of the ruby I had for refiduum, after the evapo- 

 ration of the muriatic folution, but five parts and a half of filiceous earth, 

 (lightly coloured green, and without any mixture of abimine. This dif- 

 ference arifes from the degree of heat given to the matter towards the end 

 of the evaporation, or from the faline mafs not being equally ftirrcd 

 throughout. In the latter cafe it happens that there arc paits which dry 

 top much, and others which do not dry fufficiently. Hence it happens that 

 ' jnolcculae of alumine arc abandoned by the acid, while moleculae of filcx 

 in combined ; and this was the cafe in my firft. analyfis. 



, VIII. Thefe 



