30$ POTASH IN SCHIST. 



This was ur^levtakcn for the purpose of finding the quail* 

 tity of the potash, the presence of which was certain, and 

 of the silex, which had not been obtained with certainty. 

 Third analysis. 10 gram. [154 grs.] of the fossil were kept a long time at 

 a red heat with five times their weight of caustic barytes. 

 The mixture having grown pasty, it was diluted with water 

 and pure muriatic acid. Being* evaporated to dryness, the 

 silex was collected. It weighed 7*05 gr. It was fused again 

 with potash, and diluted in water and a little sulphuric acid. 

 There was a residuum of 0*4 of a gr., to which muriate of 

 silver gave a violet colour. It was heated red hot with car- 

 bonate of potash, and washed with distilled water. The 

 liquor contained sulphuric acid. Great part of the residuum 

 dissolved in muriatic acid. It contained barytes and silver* 

 The 0*4 of a gr. therefore consisted of barytes, muriate of 

 silver, and a little silex; so that we may reckon the whole of 

 the silex at 7*1 gr. 



The barytes was precipitated from the muriatic solution 

 by sulphuric acid ; the earths, and oxide of iron, by carbo- 

 nate of ammonia. The filtered liquor having been evapo- 

 rated to dryness, a residuum was obtained, which, being cal- 

 cined with sulphuric acid, was reduced to 0*65 of a gr. It 

 was redissolved in a very small quantity of water, and con- 

 centrated muriate of platina was added to the solution. A 

 precipitate took place, which was collected. The superna- 

 tant liquor, decomposed by hidrosulphuret of ammonia, 

 filtered, and evaporated afresh, left a residuum of 0"2 of a 

 gr., consisting entirely of lime and magnesia. The least 

 trace of soda was not to be found. There remained then 

 0*45 of sulphate of potash, containing about 0*25 of alkali. 

 Method of cis- I satisfied myself, that the basis of this sulphate was pot- 

 tinguishing ^ ^y a very convenient method, which Mr. Descotils has 



Ihe tnsule of , , .- t i • i • •• 



platina with made public, and which serves immediately to distinguish 



potash from t j, e triple muriate of platina and potash from that of platina 

 that with am- . _ . . , ...* . . „A •,. 



raon'ia. and ammonia. It consists in boiliugthe precipitate m nitro- 



muriatic acid. If it be the ammoniacal salt, it is decom- 

 posed, the ammonia is burned, and the platina dissolved. 

 On the contrary, if it be the trisule with potash, it remains 

 untouched; unless the quantity of the liquor be too great, 



in 



