36 On the Chemical Compositmi of Harmoiome. 



of platinum, which was added in some excess. The whole was 

 then evaporated to dryness at a gentle heat ; tlie dry mass di- 

 gested with alcohol ; the alcoholic solution mixed with water and 

 sulphate of ammonia, and evaporated to dryness. The residue 

 was then ignited, and treated with hot water. The solution by 

 evaporation gave efflorescent crystals of sulphate of soda. 



(g^ As in this analysis the relative quantities of potash and 

 soda were not determined, a new analysis was undertaken for 

 that purpose. 13.55 grains of harmotome crystals of the same 

 form were decomposed by muriatic acid, as before, and after 

 evaporating to dryness and re-dissolving, the whole earthy con- 

 tents of the mineral were thrown down at once by carbonate of 

 ammonia. The residual chlorides obtained, as in the preceding 

 process, weighed .38. Their solution was precipitated by mu- 

 riate of platinum, and the liquid left to spontaneous evapora- 

 tion. Well characterised prismatic crystals of the double chlo- 

 ride of platinum and sodium were formed. These were taken up 

 by digestion in alcohol. The residual chloride of platinum and 

 potassium, after being well washed with alcohol, and carefully 

 dried, weighed .58, equivalent to .17726 of chloride of potassi- 

 um. By subtraction we get .20274 for the chloride of sodium. 

 On distributing, in the same proportions, the .48 of soluble resi- 

 due of the first analysis, we get .2239 of chloride of potassium, 

 and .2561 of chloride of sodium, equivalent to .14163 of potash, 

 and .13647 of soda. I prefer taking the total soluble residue 

 of the first analysis to that of the second, because the crystals 

 analyzed were better formed, and of greater purity. 



We thus have in 16.07 grains of the mineral, exclusive of 

 water 



Silica, (h) (c) (d)(f) 7.56 



Alumina, ('c^ „. 2.45 



Baryta, (e) 3.3517 



Lime, (e) 0168 



Potash, r^; 1416 



Soda, (g) 1364 



Peroxide of Iron, 03 



13.6865 



