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Scientific Proceedings (127) 



inorganic phosphate really represents all inorganic phosphate pres- 

 ent, for it might be thought that the above results are nuerely a 

 simulation of what we claim, due to limitations of the method 

 used. We, therefore, added to a sample of blood, sodium phos- 

 phate equivalent to 1 mgm. of P per 100 c.c. of blood. The table 

 shows the results. We find a complete recovery both in the in- 

 organic phosphate and the determinations after boiling within 

 the limit of error of the method. 



To demionstrate the completeness of hydrolysis of the hydro- 

 lysable substance, we have done further experiments in which 

 hydrochloric acid or nitric acid were added to the filtrate before 

 boiling. The trichloracetic acid is probably all decomposed be- 

 fore the end of the two hours boiling. Either of these acids 

 when added in amounts to produce a concentration of about N/4 

 will somewhat interfere with an accurate determination by the 

 Tisdall method, so that after two hours boiling lower results 

 are obtained. However, when we continued the boiling for four 

 hours and then applied the Tisdall method, the results were 

 identical with those obtained on boiling with only trichloracetic 

 acid present in the filtrate. (11.1 mgm. with HNO G against 

 11.3 without HN0 3 on beef blood.) 



It might still be objected that the micromethod is not applica- 

 ble. We have, therefore, repeated the experiments on a larger 

 scale, with 200 c.c. of blood filtrate using for the determinations 

 of phosphorus the well-recognized method of preliminary pre- 

 cipitation with ammonium molybdate, precipitation and repre- 

 cipitation with magnesia mixture, ending with gravimetric de- 

 terminations as magnesium pyrophosphate. The small amount 

 of phosphorus which results even from the 200 c.c. of filtrate 

 does not allow an accurate quantitative determination, but it 

 clearly shows that boiling with acid yields a relatively constant 

 figure distinctly higher than the inorganic and distinctly not 

 equal to the total phosphorus of the filtrate. 



The only objection still remaining, is the possibility of incom- 

 plete precipitation in blood filtrates by all molybdic acid reagents 

 and a partial removal of an inhibiting substance by boiling with 

 acid. A determination of the phosphate obtained by precipitat- 

 ing the blood filtrate directly with magnesia mixture (heated, 

 and allowed to stand over night) gives values which are incor- 

 rect, due to impurities in the precipitate. We have, however, 



