THE INORGANIC CONSTITUENTS OF THE URINE. 235 



of a rubber-tipped glass rod. The precipitate is washed with hot 

 water for half an hour, and at intervals of a few minutes hot 

 ammonium chloride solution (5 per cent.) is substituted for the 

 water, so that in all five or six additions of ammonium chloride take 

 place in the course of the first twenty minutes' washing. In the 

 end a specimen of the washings must no longer be rendered cloud) 7 , 

 even on standing a few minutes, after the addition of a drop of dilute 

 sulphuric acid. 



The paper filter is partially dried by folding and pressing gently 

 between filter paper. It is then placed in a weighed crucible cov- 

 ered with 3 to 4 c.c. of alcohol and the alcohol ignited. The ash is 

 heated, at first moderately, and almost completely covered with the 

 lid, then only half covered, for from five to seven minutes, until the 

 contents of the crucible are white. The crucible, when cooled, is 

 placed in a desiccator and weighed, the difference between the first 

 and second weighing giving the weight of the barium sulphate 

 obtained from 50 c.c. of urine. 



Quantitative Estimation of the Conjugate Sulphates 



(Folin). 200 c.c. of urine (diluted to a liter if necessary) are 

 treated with 100 c.c. of a 10 per cent, solution of barium chloride, 

 at ordinary temperature. The mixture is set aside for twenty- 

 four hours and the clear supernatant fluid poured into a dry beaker 

 by decanting. This preliminary decanting is necessary, as the 

 barium sulphate precipitate will otherwise go through the paper. 

 The decanted liquid is filtered, 150 c.c. of the clear filtrate repre- 

 senting 100 c.c. of urine, measured into an Erlenmeyer flask, treated 

 with 10 to 15 c.c. of concentrated hydrochloric acid and 10 to 15 c.c. 

 of a 4 per cent, solution of potassium chlorate. The mixture is then 

 heated to boiling and kept upon a boiling water-bath until the barium 

 sulphate has settled and the supernatant fluid is clear. The precip- 

 itate is filtered off, washed, dried, and weighed, as described above. 

 The weight thus obtained and deducted from the amount found 

 according to the first method, indicates the amount referable to the 

 mineral sulphates. The molecular weight of BaSO 4 being 232.82, 

 that of SO 3 79.86, of H 2 SO 4 97.82, and of S 32, the figure express- 

 ing the amount of H 2 SO 4 , SO 3 , or S, corresponding to 1 gramme 

 of BaSO 4 , is found according to the following equations : 



232.82 : 79.86 : : 1 : x ; tmdx= 0.34301. .-. 1 gramme of BaSO 4 

 = 0.34301 gramme of SO 3 . 



232.82 : 97.82 : : 1 : x ; and x = 0.420.15. /. 1 gramme of BaSO 4 

 = 0.42015 gramme of H 2 SO 4 . 



232.82 : 32 : : 1 : x ; and x = 0.13744. .-. 1 gramme of BaSO 4 = 

 0.1 3744 gramme of S. 



To calculate results, it is only necessary to multiply the weight 

 of the BaSO 4 by 0.34301, 0.42015, or 0.13744, in order to ascertain 

 the amount of sulphuric acid contained in 50 c.c. of urine, in terms 

 of SO 3 , H 2 SO 4 , or S, respectively. 



