of Organic Bodies. 23 



yet the carbon continues to glow for a long time; frequently, 

 when the quantities are not too small, for several hours ; even 

 portions taken out with the platinum spatula continue to burn. 

 The more concentrated the solution of platinum is, the more 

 readily does the combustion ensue. When the mass ceases 

 to glow on the continued application of heat, and still appears 

 black, it must be again moistened with chloride of platinum. 

 The less carbon the residue contains, the more readily does 

 the combustion ensue. If the solution of platinum is concen- 

 trated, twice moistening and heating are usually sufficient to 

 produce the combustion of the whole of the carbon. A second 

 moistening with the solution of platinum is not strictly requi- 

 site. After the mass has been once moistened and then heated 

 to redness, the residue may be treated with aqua regia and 

 evaporated, so as to render the platinum again active; how- 

 ever, this is a somewhat tedious proceeding; great care 

 must also be taken that no loss is occasioned by the spirting 

 of the mass. As the whole of the platinum used is usually 

 recovered, the method does not entail any pecuniary loss; it 

 is therefore preferable to moisten the mass a second time with 

 chloride of platinum. 



When all the carbon has been burnt, the residuary mass is 

 of a pure ash-gray colour. Before it is treated with muriatic 

 acid, it must be heated to redness in a porcelain crucible in a 

 current of hydrogen gas, so that the double compounds of the 

 alkaline chlorides with the chloride of platinum may be com- 

 pletely decomposed, which can onl}' be accomplished with 

 difficulty with large quantities by merely heating them in atmo- 

 spheric air. If the treatment with hydrogen gas be omitted, 

 the subsequent separation of the platinum from the muriatic 

 solution of the ash is accompanied with several inconveniences. 

 The mass, after having been treated with hydrogen gas, is df- 

 gested for a long time v^ith muriatic acid in a flask, the residue 

 separated by filtration, and washed with water containing mu- 

 riatic acid. The resulting solution, which usually contains 

 the same constituents as the muriatic extract of the carbon- 

 ized mass, is analysed in exactly the same manner. 



The platinum remaining undissolved, which is also mixed 

 with the sand and silica of the organic substance, may be sepa- 

 rated from these substances by two methods. The whole is 

 either boiled in a platinum capsule with a solution of carbonate 

 of soda, which dissolves the silica, leaving the platinum and 

 the sand, which may then be separated by aqua regia ; or the 

 mass is treated at once with aqna regia, when the sand ana 

 silica remain undissolved, and may be separated from each 

 other by boiling with a solution of carbonate of soda. The 



