370 Analyjis of a Stone 



I neverthelefs began to precipitate it by means of ammo- 

 nia, Which does not precipitate lime. I then poured into 

 the liquor, united to the warnings of the precipitate, fome 

 drops of a folution of common carbonat of potafh, and I 

 obtained the lime combined with the carbonic acid. I re- 

 diffolved, for the third time, in nitric acid, the earth mixed 

 with the oxyd of manganefe, and added, in fmall quantities 

 at a time, a folution of hydro-fulphuret of potafh, in order 

 that I might precipitate only the metallic parts, which, with 

 a little attention, I was able to effe6l. 



I had then the earth alone, fo that nothing was neceffary 

 to obtain it pure but to precipitate it by ammonia. 



Analyjis of the Gadolinite by Potafh. 



I Hill employed another method, which alfo fucceeded, to 

 feparate the different elements which conftitute the gadoli- 

 nite: it confifts in filling it with two parts of cauftic pot- 

 afh, wafhing the mufs with boiling water, and filtering the 

 liquor, which has a beautiful green colour. 



In evaporating this liquor, the manganefe, which gave it 

 its colour, was gradually precipitated under the form of a 

 black powder, which could be eafily collected by decanting 

 the fupernatant water. 



When it is obferved that there is no more oxyd of manga- 

 nefe, the liquor muft be faturated with nitric acid : on the 

 other hand, the fediment muft be put to digeft with the fame 

 acid much diluted with water : by thefe means the earth 

 alone diflblves, producing a great deal of heat ; and the filex, 

 and the iron too much oxydated, do not diffolve. 



This folution with the above liquor, faturated with nitric 

 •acid, muft be evaporated to drynefs, in order that if any parts 

 of iron and filex have remained they maybe Separated : in other 

 refpe&s the procefs is the fame as before. The latter has 

 the advantage of feparating the manganefe from the other 

 principles, and of rendering unneceffary an operation the 

 fuccefs of which is difficult. 



The gadoli lite might alfo, rigoroufly fpeaking, be ana- 

 lysed by directly attacking it by the fulphuric and muriatic 

 acids; but as thefe acids diffolve at the fame time, and 



without 



