20 Prof. H. Rose on the Inorganic Constituenls 



nionio-pliosphate of magnesia after it has been heated to red- 

 ness. 



By the analysis of the phosphates precipitated by ammonia, 

 the composition of the precipitated phosphate of lime and the 

 presence or absence of the perphosphate or pure peroxide of 

 iron in the precipitate may be determined. The liquid filtered 

 from the earthy phosphates contains either alkalies and phos- 

 phoric acid only, as is the case in the examination of allseeds 

 and animal matters, or it contains lime and magnesia only, 

 and these frequently in very considerable quantities. They 

 existed in the carbonized mass in the form of carbonates ; but 

 it is only in those cases in which they are present in consider- 

 able quantities, as in the analyses of the straw of peas and rape, 

 that a very distinct evolution of carbonic acid can be per- 

 ceived on treating the carbonized mass, after exhaustion with 

 water, with muriatic acid. As the carbonic acid cannot be 

 determined directly, it is calculated from the quantity of lime 

 and magnesia found in the liquid filtered from the earthy 

 phosphates. 



In the analysis of the carbonized mass of vegetable seeds 

 and animal substances, where, as has been previously men- 

 tioned, the liquid filtered from the earthy phosphates contains 

 both alkalies and phosphoric acid, this is treated with chloride 

 of barium; phosphate and, when sulphuric acid is present, 

 sulphate of baryta are then precipitated. Sulphuric acid has, 

 however, very rarely been found in the muriatic extract of the 

 carbonized mass. The phosphate of baryta is separated by 

 filtration, dissolved in muriatic acid, the baryta precipitated 

 from the solution by sulphuric acid, which is then supersatu- 

 rated with ammonia, and the phosphoric acid precipitated as 

 ammonio-phosphate of magnesia. 



The liquid which was separated from the phosphate of 

 baryta contains the alkalies. The excess of baryta is removed 

 by carbonate of ammonia, the filtered solution evaporated to 

 dryness, and the dry mass heated to redness to expel the am- 

 moniacal salts. The alkaline chlorides left are separated by 

 chloride of platinum. 



The examination of the second portion can be considerably 

 simplified when sulphuric acid is absent. The muriatic extract 

 is carefully evaporated. If it contains silica, the dry mass is 

 moistened with nitric acid, and the silica separated ; mercury 

 and nitric acid are added to the filtered liquid ; it is then eva- 

 porated to dryness with excess of mercury in the ordinary 

 way, and the bases separated from the phosphoric acid by 

 water. 



This simplified method has, however, two disadvantages. 



