344 ANALYSIS OF URINE. [CH. xill . 



and beaker. Now transfer the paper, precipitate and disc to the 

 marked beaker, by means of a glass rod which has a fine curved point. 

 Remove the funnel from the filtering flask and wash it down into the 

 beaker with a jet of hot water. Also wash the pointed glass rod. 

 Add hot water to make a total volume of 100 cc., as indicated by 

 the label. Add 20 cc. of the 45 per cent, sulphuric acid and stir 

 with a thermometer. The whole of the precipitate must be dis- 

 solved, if necessary by the aid of heat, before the titration is com- 

 menced. Cool or heat to 65 C. Titrate with the standard perman- 

 ganate, reading the meniscus by the aid of a lighted match held 

 behind the burette. The permanganate must be added rather 

 slowly, with constant stirring. The end point is reached when the 

 addition of a couple of drops causes a faint pink flush through the 

 whole body of the fluid. A very considerable addition has to be 

 made for the pink to be permanent, but the empirical valuation of 

 the permanganate is based on the end point described above. 



Calculation. Since 150 cc. of the urine were treated with 30 cc. (one- 

 fifth volume) of colloidal iron, 6 cc. of the filtrate from this correspond to 5 cc. 

 of urine. 



If u cc. of the filtrate have been taken and .p cc. of 0-05 N. permanganate 

 used, then u cc. contain/) x 3-7 mgms. uric acid, and 100 cc. of urine contain 



6 100 i p 



p x 3-7 x jx -jj- x-^ gram. = - x 0-444 gram. 



NOTE. Whilst this edition was passing through the press the author 

 has found that the best method of filtering off the urate is to use a Hirsch 

 funnel with a fixed perforated plate, and to use asbestos instead of paper 

 pulp. The filtering mat is prepared in the way described for a Gooch 

 crucible (seep. 389), the drying being omitted. The mat with the layer of 

 urates can be very neatly removed and the whole process is much facilitated. 

 The time required for the estimation is considerably overstated above. The 

 whole process can be accomplished in 40 minutes, it being unnecessary to 

 allow the fluid to stand for more than 10 minutes after the addition of the 

 ammonia. 



G. Glucose. 



The estimation of sugar in urine when there is a considerable amount 

 present can be carried out by any of the standard methods, as, owing to the 

 dilution necessary or the small amount required, there is little interference 

 by the normal urinary constituents. If the concentration is less than 0-8 per 

 cent, the author prefers to use the Wood-Ost method (p. 131), and to dilute 

 the urine at least three times with water. Though the amount of permanga- 

 nate required is small, the results are quite satisfactory. With Benedict's 

 method of direct titration (p. 127) the end point is apt to be very uncertain 

 with low concentrations of sugar. The polarimetric method referred to on 



