326 ANALYSIS OF URINE. [CH. XIII. 



To the fluid thus obtained add a few drops of a 0-02 per cent, 

 solution of methyl red and titrate with standard CO 2 - free sodium 

 hydroxide, which may be between o-i and 0-15 N. 



Calculation, see p. 323. 



395. Kjeldahl's method (steam distillation). The incinera- 

 tion is conducted as described in the previous exercise, but a 

 smaller Kjeldahl flask may be used if desired. After the fluid 



Fig. 41. Kjeldahl apparatus. Steam distillation. 



has cooled, add 50 cc. of distilled water, shake round well and 

 transfer the solution to D, a round-bottom flask of i or 2 litres, 

 with a neck sufficiently wide to carry a well-fitting rubber stopper 

 that will allow 3 tubes to pass through, as shewn in the figure. 

 Wash out the Kjeldahl flask twice more, using about 25 cc. of 

 distilled water each time. Measure the requisite amount of standard 

 acid into K, and assemble the apparatus. Arrange the wooden 

 blocks, L, so that the end of the delivery tube, H, just dips under 

 the surface of the acid. (It is incorrectly drawn in the figure.) E is 

 a tap-funnel containing 40 per cent. soda. G is a condenser, the 

 double-surface variety being the most efficient. 



