THE COMPOSITION AND CHARACTERS OF THE URINE 1179 



sulphocyanate which has been previously standardised against the silver solution, a 

 ferric salt being used as indicator. 



The following solutions are required : 



(1) Standard silver nitrate solution either -- or so that 1 c.c. corresponds to -01 grm. 



NaCl. 



(2) Potassium sulphocyanate solution (8 grm. per litre). 



(3) Pure HNO 3 free from chlorides. 



(4) A saturated solution of iron alum. 



The potassium sulphocyanate solution must be standardised against the silver nitrate 

 solution. This is carried out as follows : Place 10 c.c. AgN0 3 solution with a pipette 

 in a beaker, add 5 c.c. pure HN0 3 , 5 c.c. iron alum solution, and 80 c.c. water. Now 

 run in the sulphocyanate solution from a burette until a permanent red tinge is obtained. 

 Note the amount required for the 10 c.c. AgN0 3 solution. 



The method of analysis is carried out as follows : Place 10 c.c. urine in a 100 c.c. 

 measuring flask with a pipette. Then add about 4 c.c. pure nitric acid and 10 or 20 c.c. 

 with a pipette of the standard silver nitrate solution. Now fill up to the mark with 

 distilled water, mix thoroughly, and filter into a dry vessel through a dry paper. Take 

 exactly 50 c.c. of the filtrate with a pipette and titrate with the sulphocyanate solution 

 until a permanent red colour is obtained, iron alum having been added before the titra- 

 tion is commenced. Calculation of results : 



50 c.c. filtrate = S c.c. KCNS 

 .-. 100 c.c. = 28 c.c. 

 Now x c.c. KCNS = 10 c.c. AgN0 3 



This is the excess'not utilised to precipitate the chlorides 



10 x 2$\ 

 .-. (20 ' J = amount of AgN0 3 solution used. 



From this the amount in grammes of NaCl passed in the urine in twenty-four hours 

 can be calculated. 



ESTIMATION OF PHOSPHATES. The method depends upon the precipitation 

 of all the phosphates by a standard solution of uranium acetate or uranium nitrate in 

 the presence of sodium acetate and acetic acid as (Ur 2 )HPO 4 . The determination of 

 the end-point, when soluble uranium salt is in solution, is shown by means of potassium 

 ferrocyanide, or by cochineal tincture which becomes green. 



The following reagents are required : 



(1) Acid sodium acetate solution (100 grm. NaAc, 30 grm. HAc, 1000 c.c. H 2 O). 



(2) Cochineal tincture (5 grm. cochineal extracted for several days with 150 c.c. alcohol 



and 100 c.c. water and then filtered). 



(3) Standard uranium solution (1 c.c. = '005 grm. P 2 O 5 or 5 mg.). 



This must be prepared by standardising against a standard phosphate solution. 

 Generally sodium phosphate is employed ; about 12 grms. are weighed out and dissolved 

 in 1000 c.c. water; 50 c.c. of this solution are evaporated to dryness, incinerated, and 

 weighed as pyrophosphate. From the weight of this the amount of P 2 5 in 50 c.c. can 

 be calculated and the remainder of the solution can be diluted, so that 50 c.c. contain 

 O'l grm. P 2 5 . It is simpler to use acid potassium phosphate, KH 2 P0 4 , which can be 

 weighed directly and dissolved in water, so that 50 c.c. contain 0*1 grm. P 2 5 . Fifty 

 cubic centimetres of this solution are titrated with the uranium solution (36 grm. in 

 one litre) in the manner described below, and the uranium solution is then diluted so 

 that 1 c.c. = 5 mg. P 2 5 . 



The method of analysis is carried out as follows : Place 50 c.c.- urine with a pipette 



