jt|o Hfemoir on the Stones faid ta 



If we might Aippofe that the iron contained in this ftone 

 exifts in the perfect metallic ftate, we might eafily find, by 

 the increafe of weight which it acquires in confequence of 

 oxygenation, the proportion of fulphur; but as it is certain 

 that this metal is oxidated in it in an unknown quantity, that 

 of (he fulphur cannot be determined. 



A hundred parts of this ftone, freed as far as could poflibly 

 be done from ferruginous matters, were treated with muri- 

 atic acid diluted with a little water. The mixture produced 

 immediately, with a ftrong effervefcence, a gas which had 

 the odour of fulphurated hydrogen gas. The matter affumed 

 the form of a gelatinous mafs, which feems to prove, as al- 

 ready faid, that the filex exifts in this ftone in a ftate of com- 

 bination either with iron or with other fubftances. 



When the effervefcence had fubfided, and the mixture had 

 boiled for fome time, it was diluted with water and filtered. 

 The liquor had a green colour analogous to that of muriate 

 of iron, but a little darker. The refiduum when wafhed was 

 white, and weighed 49 parts. 



The muriatic folution and wafhings being united together 

 were precipitated by ammonia added in excefs, and were 

 ftirred for fome time with the precipitate. 



It has been remarked, that oxidated iron, precipitated in 

 this manlier by ammonia, has a more intenfe colour than 

 that of iron obtained under the fame circumftances. This 

 iron, waflied and dried, weighed 42 parts. 



The liquor containing the fuperabundant ammonia in the 

 precipitation of the iron had acquired a violet colour, which 

 neither the heat nor the contaft of the air made it lofe. Al- 

 kaline carbonates produced in it no alteration ; on the other 

 hand, fixed cauftic akalies formed in it a white precipitate 

 pretty abundant, which when waftied and calcined weighed 

 twelve parts. This matter combined with fulphuric acid 

 gave fulphate of magnefia, coloured green by a fmall quan- 

 tity of nickel which the magnefia had carried down with it. 



The liquor from which this earth had been feparated by 

 potafli had loft a part of its violet colour; it, however, ftill 

 formed a black precipitate with fulphurated hydrogen. From 

 what I had before obferved, 1 entertained no doubt that the 

 fubftance which coloured the magnefia green, and was pre- 

 cipitated black by hodro-fulphuret of ammonia, was nickel. 

 I therefore feparated, by means of this reagent, the portion 

 which remained in folution and that which was mixed with 

 the fulphate of magnefia: I united them, and having cal- 

 cined them to feparale the fulphur, I obtained a green oxide, 

 which weighed three parts and a half. 



The 



