of Organic Bodies. 21 



The large amount of chlorine present produces a large quan- 

 tity of protochloride of mercury, which remains mixed with 

 the protophosphate of mercury ; hence this insoluble mixture 

 requires a large quantity of carbonate of soda for its decom- 

 position. The second disadvantage is, that when the earths 

 form the principal constituents of the acid extract, it cannot 

 be accurately determined whether they are combined with 

 phosphoric or carbonic acid. 



Part III. — This part of the investigation comprises the de- 

 termination of the inorganic constituents existing in the car- 

 bonized mass after exhaustion with water and muriatic acid, or 

 rather which are produced by oxidation. 



This incineration of the carbonaceous mass is accompanied 

 by no small difficulties. 1 formerly effected it by heating it to 

 redness in a crucible, the lid of which was perforated, and a 

 silver tube, which conducted a current of oxygen to the heated 

 mass, was fitted to the aperture. The incineration succeeded 

 perfectly in this manner; but in a very large number of cases 

 it was impossible to incinerate the carbonized mass merely by 

 the access of atmospheric air without the aid of oxygen. But 

 on combustion in oxygen gas, an elevated temperature is pro- 

 duced and the substance of the crucible is powerfully attacked 

 by the phosphates formed by the oxidation. If a platinum 

 crucible be used, it is completely spoiled when alkaline phos- 

 phates and carbon act upon it at an elevated tempera- 

 ture. Nor can a porcelain crucible be used ; because when 

 the greater portion of the carbon has been burnt, the alkaline 

 phosphates, being in a state of fusion, dissolve the glaze. This 

 is particularly the case with porcelain crucibles of Meissen 

 manufacture ; but even those manufactured at Berlin cannot 

 resist the action, although they are far less acted upon than 

 the former. Silver crucibles do not stand the high tempera- 

 ture, and begin to melt. When the combustion of the car- 

 bonized mass is effected in a glass tube heated to redness in a 

 furnace by a charcoal fire, it succeeds tolerably well ; but the 

 high temperature produced by the combustion of the carbon 

 in oxygen fuses the alkaline phosphates, and they unite with 

 the glass, so that they cannot afterwards be separated from it 

 mechanically. The combustion was finally effected in small 

 earthenware crucibles, which answered in every respect tole- 

 rably well, and were but slightly acted upon by the alkaline 

 phosphates; but one important difficulty still remained un- 

 conquered, — a considerable quantity of alkaline phosphate 

 is constantly volatilized. This is very large; and the vola- 

 tilization cannot in any way be avoided when the combus- 

 tion is effected in oxygen gas, even when the current is slo\y. 



