348 PHYSIOLOGICAL CHEMISTRY. 



Calcium phosphate > 85.7 per cent. 



Magnesium phosphate 1.5 



Calcium carbonate i i.o " 



Calcium fluoride and chloride i.o 



Ferric oxide 0.8 " 



100.0 



The presence of calcium, magnesium and phosphoric acid 

 may be shown in the weak hydrochloric acid extract of the 

 bone described above. 



Ex. To a few cubic centimeters of the filtered solution add some 

 ammonium molybdate solution. In a short time a yellow precipitate 

 appears, indicating presence of a phosphate, as familiar to the student 

 from the reactions of qualitative analysis. 



Ex. To a few cubic centimeters of the solution add solution of sodium 

 acetate until a distinct odor of acetic acid persists. Then add some solu- 

 tion of ammonium oxalate, which produces a white precipitate of calcium 

 oxalate. 



Ex. To another portion of the hydrochloric acid solution add ammonia 

 until a good alkaline reaction is obtained. A white precipitate of calcium 

 and magnesium phosphates settles out. Filter, and to the filtrate add 

 some ammonium oxalate solution. A further precipitate appears. This 

 is calcium oxalate and proves that the original solution contains calcium 

 in excess of that combined as phosphate. The calcium of the carbonate, 

 fluoride and chloride appears here. 



Ex. To detect the small amount of magnesium requires greater care. 

 To another and relatively large portion of the acid solution add enough 

 ammonia to give an alkaline reaction, and then acidify slightly with acetic 

 acid. This dissolves everything except ferric phosphate, which may be 

 filtered off and tested for iron. To the filtrate add enough ammonium 

 oxalate to precipitate all the calcium as oxalate. Separate this after long 

 standing by means of close-grained filter paper. In the clear filtrate the 

 magnesium may be thrown down with the phosphoric acid still present, 

 by the addition of ammonia water in slight excess. 



Bone Marrow. The pure marrow consists largely of fat 

 in which olein is abundant; cholesterol is present and some 

 nitrogenous extractive substances, which, however, have not 

 been very thoroughly examined. 



CARTILAGE. 



Collagen is probably the most abundant substance in the 

 cartilaginous tissue where it exists mixed or combined with 

 several other bodies, of which these have been described : 



