558 Drushel — Estimation of Potassium in Animal Fluids. 

 K 2 0* 2 to 4 grm. Urea 30 grm. 



NaCl 10 " 15 



CaO and MgO 0*8 



NH 3 0-7 



P 2 5 (phosphates) 1*5 



H 2 S0 4 (sulphates).... 2-5 



Uric acid 0*7 



Creatinine _ 1*5 



Hippuric acid ._ 0*7 

 Other organic ._ 

 bodies 2*1 



a 



In this list of constituents ammonia and the organic bodies, 

 especially urea, are the only ones which should interfere with 

 the volumetric method as previously described. To remove 

 these bodies without the loss of potassium is apparently the 

 only new problem. 



In the experiments recorded in Table 1 aliquot portions of 

 urine of 10 to 50 cubic centimeters each were measured with 

 pipettes or a burette into small platinurn evaporating dishes, 

 and evaporated to dryness over the steam bath in a good 

 draught hood. The residues of the aliquots of the first speci- 

 men were treated with 5 cm3 of concentrated nitric acid and 

 again evaporated to dryness. These residues were then moist- 

 ened with concentrated sulphuric acid and ignited to a white 

 ash beginning with a low flame and increasing the heat until 

 the organic matter was burned off, and the ammonium sulphate 

 and excess of sulphuric acid completely removed. In subse- 

 quent experiments it was found more expeditious to treat the 

 dried urine residue with 5 cm3 to 10 cm3 of a 9 : 1 nitric-sulphuric 

 acid mixture, in a covered evaporating dish, removing the 

 cover when the first violent oxidation is over, evaporating to 

 dryness and igniting without the further addition of sulphuric 

 acid. By this treatment the ignition of the residue from 50 cm3 

 of urine could be readily made in 30 minutes without loss of 

 material. The residue thus prepared was treated with a little 

 water and a few drops of acetic acid to dissolve the alkalis. 

 Without filtering about 10 cm3 of concentrated sodium cobalti- 

 ' nitrite were added and the mixture evaporated to a pasty 

 condition. From this point the process was carried out as 

 previously described. In the control experiments the phos- 

 phoric acid was removed by a slight excess of calcium hydroxide, 

 and the calcium by ammonium oxalate, before the ignition of 

 the residue. 



The results obtained by the two methods from a number of 

 different specimens of human urine are given in the following 

 table. 



B. Potassium in circulatory fluids. 



An additional difficulty presents itself here in the presence 

 of a large amount of protein material which can not be removed 

 by coagulation and filtration without a considerable loss of 



* Taken from Hammerstein's Physiological Chemistry, (Mandel's Trans- 

 lation), 5th ed., p. 628. 



