166 Dr. Percy on the Composition of Beudantite. 



rium. The precipitate, washed, dried and ignited, weighed 

 2-00 grs*. 



Loss by calcination^ determination of arsenic. — 3* 54 grs. of 

 the mineral reduced to powder were heated in a small closed 

 tube of Bohemian glass for a considerable time ; first over the 

 spirit-lamp, and afterwards at a bright red heat before the 

 blowpipe. The loss in calcination was 040, the calcined 

 mineral weighing 3*14 grs. This residue was red-brown, like 

 sesquioxide of iron. It was dissolved in hot hydrochloric acid, 

 and chloride of barium was added to the solution. The pre- 

 cipitate, washed, dried and ignited, weighed 0*90 gr. 



The solution was freed from baryta by sulphuric acid: ex- 

 cess of ammonia was added, and afterwards hydrosulphate of 

 ammonia. The determination of the arsenic was made as 

 previously described. The analytical data are as follow: — 

 Sulphur and sulphuret analysed weighed 3*13 

 Sulphur and sulphuret adhering to filter 0*07 



Free sulphur 0*50 



Sulphate of baryta 17*24 



Determination of Sulphuric Acid in part of the same specimen 

 of mineral used in the last determination. 

 2*40 grs. were dissolved in hydrochloric acid. Chloride of 

 barium was added. The precipitate, washed, dried and ig- 

 nited, weighed 0*83 gr. 



Results Tabulated. 

 First Analysis. 

 Weight of mineral 6*17 grs. 



Arsenic by loss 0*39 = 6*32 per cent. =9*68 (As O 5 ). 

 Phosphate of magnesia 0*14 = *09 (PO 5 ) = P46 per cent. 

 Sulphate of lead 2*05 = 1*51 (PbO) =24*47 per cent. 

 Sesquioxide of iron 2'62 = 42*46 per cent. 



Second Analysis. 

 Weight of mineral 6*64 grs. 

 Sulphate of lead 2*66= 1*96 (PbO) =29*52 per cent. 



* On the Separation of Sulphuric Acid from Su'p/iafe of Lead by Chloride 

 of Barium. — As the mineral under examination container] sulphuric acid and 

 oxide of lead, the correctness of the preceding determination of sulphuric 

 acid was tested by the following experiment. Of sulphate of lead, which 

 had been prepared some years previously, and of the absolute purity of 

 which I was not certain, 23*92 grains were weighed after heating, and dis- 

 solved in hot hydrochloric acid. The acid solution was poured into a hot 

 solution containing more than 20 grains of chloride of barium. The sul- 

 phate of baryta, washed, dried and ignited, weighed 1804. Now 2392 of 

 sulphate of lead contain of sulphuric acid 620, and 1804 of sulphate of 

 baryta contain of sulphuric acid 6*32. These results are sufficiently sa- 

 tisfactory. 



