560 Drushel — Estimation of Potassium in Animal Fluids. 



potassium. This is particularly true of the blood, where most 

 of the potassium is intimately associated with the protein of 

 the corpuscles. It is necessary therefore to decompose the 

 protein material by oxidation. 



The nitric-sulphuric acid mixture was first used for oxidizing 

 the dried blood residue, but was found to work less satisfac- 

 torily than in the case of urine. In the ignition of the blood 

 residue oxidized in this way there was apparently a greater 

 tendency to spatter, probably due to the presence of the sul- 

 phuric acid. When, however, nitric acid alone was used for 

 the oxidation, there was a tendency for the residue to burn off 

 explosively on ignition. The analytical results from the first 

 specimen given in Table II were obtained by treating weighed 

 portions of defibrinated blood with about 2 cm3 of bromine 

 in covered evaporating dishes, allowing them to remain in a 

 warm place under the hood for about one hour. The excess 

 of bromine was then removed over the steam bath, the residue 

 evaporated to dryness, and ignited sufficiently to char the 

 organic matter. The residue was thoroughly extracted with 

 hot water and the extract evaporated off with a few drops of 

 sulphuric acid. The residue was then ignited to remove any 

 ammonium salt which might have escaped the action of the 

 bromine and any organic matter which might have passed 

 through the filter. 



The second specimen was a half liter of clotted sheep's 

 blood, from which no homogeneous portions could be taken. 

 The whole mass was, therefore, evaporated over a steam bath 

 and oxidized with concentrated nitric acid, getting everything 

 into solution except a little lipoid material. The solution was 

 made up to the original volume, and aliquots of 25 cm3 , repre- 

 senting 30 grm. of blood, were pipetted off. These portions 

 were evaporated to dryness and gently ignited, but not suffi- 

 ciently to produce explosive decomposition. The residues 

 were then moistened with concentrated sulphuric acid and 

 ignited carefully to remove the organic matter and the ammon- 

 ium salts. For the results of the second and third divisions of 

 Table II weighed portions of serum and lymph were similarly 

 oxidized with nitric acid and subsequently ignited with a little 

 sulphuric acid. The potassium in all the residues thus obtained 

 was estimated gravimetrically or volumetrically as previously 

 described. The results obtained for potassium in circulating 

 fluids are given in the following table. 



C. Potassium in milk. 



In addition to lactose and the inorganic salts, milk contains 

 a large amount of protein, chiefly casein, and varying amounts 

 of fat. The ease with which casein is precipitated suggested 

 the possibility of making a complete separation of the inorganic 

 salts and casein, but it was found that after thoroughly wash- 



