182 METHODS FOR THE ANALYSIS OF BLOOD 



ing the process. The extracts kept cool in the dark and tightly 

 stoppered will remain unchanged for two or three months. They 

 may also be used for determination of other blood lipoids as well 

 as " lecithin." 



Alcohol-ether has been found to make an exact separation of 

 the lipoid from the acid-soluble forms of phosphoric acid com- 

 bination in blood. Tests have been made for water-soluble phos- 

 phoric acid in these extracts. At no time was there found more 

 than a trace of phosphoric acid which may have originated from 

 the lecithin even in cases of severe nephritis where the inorganic 

 phosphate was known to be much above the normal value. As 

 further confirmation of the completeness of the separation, the 

 sum of acid-soluble and lipoid phosphoric acid has been found in 

 both plasma and corpuscles to be very nearly equal (probably 

 within the limits of error of the various determinations) to the 

 total phosphates. Hence if one is known the other may be deter- 

 mined by difference with a good degree of accuracy. 



Because of the tendency of the unknown phosphoric acid con- 

 stituent of the acid ammonium sulfate extract (especially that from 

 the corpuscles) to decompose, yielding phosphoric acid, the deter- 

 minations of inorganic phosphate should be carried out at once 

 after filtering. 



Cold (room-temperature) extraction with acid ammonium 

 sulfate for at least ten minutes was found to give complete extrac- 

 tion of both inorganic and unknown acid-soluble phosphoric acid 

 in whole blood and plasma but not of the unknown in the cor- 

 puscles. For this reason heating for two minutes was necessary 

 to recover all of this substance from the corpuscles. Whether 

 heating increased the amount of inorganic phosphoric acid ex- 

 tracted from corpuscles could not be determined because heat- 

 ing decomposes the unknown, yielding phosphoric acid. For 

 that reason inorganic phosphates could be determined only in the 

 extract made in the cold. Since, however, cold treatment gave 

 complete extraction of inorganic from plasma and since added 

 phosphate was completely recovered from corpuscles by the cold 

 extraction, it is believed that it is adequate for the determi- 

 nation of inorganic phosphates in the corpuscles. 



To avoid a multiplicity of standards, directions are given for 

 the use in most cases of a single standard. In case a single deter- 

 mination is to be made on a large number of samples it is better 



