366 Analysis of Earths, 



sokuion, namely, lime, magnesia, and alumlne. In order 

 to separate them, proceed as follows : 



X. Boil the precipitaite in a ?okuion of caustic potash for 

 at least half an hour, dilute the fluid with water, and se- 

 parate the insoluble part by the lilter, the alumine will now 

 be dissolved bv the potash, and the other earths remain un- 

 touched. 



XI. To separate the alumine, neutralize the alkaline so- 

 lution by muriatic acid ; a precipitate falls down ; wash it, 

 and expose it to a red licat. It is the alumine which was 

 contained in the mineral. 



Xri. To separate the other earths, dissolve the residue of 

 Process X in nitric or muriatic acid, evaporate the solution 

 to drvncss, weigh the dry mass, and pour on it at least 

 double its weig'ht of sulphuric acid, and heat the mixture 

 till no more white ftimes rise. Digest the mass in twice 

 its weight of cold water, filter itj and dry the insoluble part 

 in a low red heat* 



XIII. The insoluble portion of the last process contain;; 

 tl)c lime combined with sulphuric acid. To ascertain iti* 

 quantity deduct from its weight 39 per cent, j the remainder 

 is the quantity of lime. 



XIV. To obtain the magnesia, concentrate the fluid ob- 

 tained in the Xllth Process to one-third of its original bulk ; 

 make it boiling hot and decompose it by a solution of car- 

 bonate of potash ; collect the precipitate, expose it to a red 

 heat till it does not eftervcsce by the addition of an acid. 

 It will then be the pure magnesia contained in the mineral. 



Stones insolulle in Diluted Nitric and Muriatic Acidsi 

 Process I. Take a determinate quantity of the stone re- 

 duced to an impalpable powder, mix it with at least three 

 times its weight of potash, and fuse the mass thoroughly 

 in a silver or platina crucible. From the phienomcna which 

 take place during this process, we may already form some, 

 conjecture concerning the nature of the stone submitted to 

 examination. If the mass fuses completely, siliceous earth 

 predominates ; but if the fusion remains imperfect, and the 

 mass cannot be rendered liquid, the other earths arc most 

 abundant. If it remains in a powdery form, and can partly 

 be rendered liquid, and if the bulk of the niass has been 

 considerably increased, then alumine mav be expected to be 

 the most prevalent part. If the mass in the crucible be of 

 a brownish red colour, it contains oxide of iron : a bright 

 green colour announces the presence of manganese, espe- 

 cially 



