Drushel — Estimation of Potassium in Animal Fluids. 557 



posing it with boiling sodium hydroxide. Later it was found 

 that a half saturated sodium chloride solution is preferable to 

 cold water for washing the precipitate since it permits the 

 use of a coarser asbestos felt in filtering without danger of loss. 



The method used in the work on animal fluids is as follows : 

 A potassium salt solution was obtained free from mineral acids 

 and ammonia salts and treated with a liberal excess of concen- 

 trated sodium cobalti-nitrite in an evaporating dish. The mix- 

 ture was evaporated to a pasty condition over the steam bath. 

 After cooling the residue it was stirred up with enough cold 

 water to dissolve the excess of sodium cobalti-nitrite. The 

 precipitate was permitted to settle a few minutes, then it was 

 filtered on asbestos in a perforated crucible and washed with 

 the sodium chloride solution until the filtrate came through 

 colorless. The precipitate and felt were transferred by means 

 of a spray of water and a stirring rod to a beaker containing a 

 measured amount (being an excess) of standard decinormal or 

 fifth normal potassium permanganate, diluted about ten times 

 and heated nearly to boiling. The permanganate solution was 

 kept hot and stirred to facilitate the solution and oxidation of 

 the precipitate, the oxidation being completed by adding 5 cm3 to 

 10 cm3 of dilute sulphuric acid and stirring for a minute or two. 

 The excess of permanganate was then bleached by a measured 

 amount of standard decinormal oxalic acid, and the solution 

 titrated to color with standard permanganate. In this process 

 the cobalt is reduced to the bivalent condition and the nitrites 

 oxidized to nitrates, from which by a simple calculation it is 

 found that one cubic centimeter of strictly decinormal perman- 

 ganate is equivalent to 0*000857 grm. of K 2 0. 



The modified Lindo-Gladding method was used as a control 

 in the experimental work of this paper. The potassium was 

 obtained as the sulphate in the presence of sodium sulphate, 

 and possibly traces of calcium and magnesium sulphate. The' 

 solution of these sulphates was treated with an excess of chlor- 

 platinic acid, evaporated nearly to dryness, and the precipitate 

 washed free from the excess of chlorplatinic acid with 85 per 

 cent alcohol. The precipitate was then washed three or four 

 times with a 20 per cent solution of ammonium chloride satur- 

 ated with potassium chlorplatinate, and finally again two or 

 three times with 85 per cent alcohol. By this treatment the 

 sodium sulphate and the small amounts of calcium sulphate 

 and magnesium sulphate are completely removed. 



A. Potassium in urine. 



The following table gives approximately the amount of the 

 constituents present in a day's excretion of urine of an adult 

 in normal health and on an ordinary mixed diet : 



