Analyjis of the Spinel Ruby. 4? 



method I employed, and whatever cafe I took, T could never 

 obtain a larger quantity, and therefore it is very probable 

 that Klaproth was deceived in this refpeel:. 



Now, to eftabliih the proportions of the principles of tn$ 

 ruby, I mull here obferve, that of ioo parts fubjefted to 

 analyfis, 97 only were attacked; but 97 having furnifhed 

 85 of alumine (Exp. XII.), 3 of which were to be taken 

 away for the filiceous earth, 100 would have given 82*47 > 

 8*5 of magnelia having been obtained from thefe 97, 8*78" 

 would have been found in 100. In the like manner, inftead 

 of 6 of the chromic acid, we mould have had 6* 18, Thus, 

 100 parts of fpinel ruby confift of alumine 82*47, magnefi* 

 878, chromic acid 6 - i8, Lofs 2'SJ. Total 100. 



XIII. To prove the corre&nefs of the refults of the pre-' 

 ceding analyfis, I repeated it by following another method / 

 I heated ICO parts of ruby,, reduced to a fine powder, for fe- 

 veral hours with concentrated fulphuric acid. I obtained a 

 folution, almoft complete, by the addition of a fufficient 

 quantity of water. There remained nothing but 5 or 6 parts 

 of a grey powder, which had all the characters of filiceous 

 earth, and which was only mixed with a little chrome. 



The folution evaporated to the confidence of fyrup gave 

 radiated cryftals without folidityj but thefe cryftals, re-dif- 

 fblved in water, and the folution mixed' with a fumcient 

 quantity of the fulphat of potafii, gave octaedral cryftals of 

 alum. The whole ioo parts of the ruby thus diffolved in the 

 fulphuric acid furnifhed me, in feveral fucceifive cryftallifa- 

 tions, with about 800 parts * of alum, without reckoning the 

 latter portions which I could not entirely feparate from the 

 mother water. This mother water had a green colour, and 

 a bitter {lightly metallic tafte. I diluted it with water, and 

 mixed with it a folution of the carbonat of potaih. There 

 was formed a grcenifh white precipitate, which was a mix- 

 ture of alumine and the oxyd of chrome. The liquor filtered 



■'■ The f une ankle in the Anuale; de Chemic, Mdfidcr An, VI ftates 

 rim product ut 775. Ewt* 



and 



