PHOSPHATES. 761 



was necessary to produce the final reaction, then for 100 cc. of the filtrate 

 ( = 10 cc. urine) 9.2 cc. of this solution are necessary. 9.2 cc. of the 

 sulphocyanide solution corresponds to 4.6 cc. of the silver solution, 

 and since 204.6 = 15.4 cc. of the silver solution was necessary to com- 

 pletely precipitate the chlorine in 10 cc. of the urine, then 10 cc. con- 

 tains 0.154 gram of NaCl. The quantity of sodium chloride in the urine 

 is therefore 1.54 per cent, or 15.4 p. m. If we always use 10 cc. for the 

 determination, and always 20 cc. of AgNOa solution, and dilute with 

 water to 100 cc., the quantity of NaCl in 1000 parts of the urine is found 

 by subtracting from 20 the number of cubic centimeters of sulphocyanide 

 (R) required with 50 cc. of the filtrate. The quantity of NaCl p. m. 

 therefore under these circumstances = 20 R, and the percentage of 



XT , 20-R 

 NaC1= __ 



If it is necessary to destroy the organic urinary constituents before titration, 

 this can be best performed, according to DEHN, 1 by evaporating the urine (10 cc.) 

 to dryness on the water-bath after the addition of a small amount of sodium per- 

 oxide, then faintly acidifying with nitric acid and then titrating according to 

 VOLHARD. Incineration is unnecessary. 



For the approximate estimation of chlorine in the urine EKEHORN has made 

 use of VOLHARD'S titration method by using for the determination a glass tube 

 closed at one end and divided into half cubic centimeters and called the chlorom- 

 eter. The reagents necessary are: (a) a mixture of 20 cc. silver-nitrate solution 

 (according to VOLHARD), 5 cc. nitric acid and water to 100 cc.; (6) 40 cc. sul- 

 phocyanide solution and 60 cc. of a ferric alum, chlorine free and saturated at 

 the ordinary temperature. The silver-nitrate solution, of which each cubic 

 centimeter corresponds to 0.002 gm. NaCl, is equivalent to the iron sulphocyanide 

 solution. First 2 cc. of the urine are placed in the graduated tube and then 0.5 

 cc. sulphocyanide solution, and the silver-nitrate solution gradually added (shak- 

 ing the tube closed with a rubber stopper) until the coloration of the sulphocyanide 

 just disappears. 0.5 cc. is subtracted from the silver solution for the 0.5 cc. of 

 the sulphocyanide; the tube is so graduated that the quantity of NaCl in the 

 urine in parts per thousand is read off directly on the tube. The difference 

 between these results and those obtained by VOLHARD'S titration method amounts 

 only, according to C. TH. MORNER,* to 0.25 to at most 0.5 p. m. 



The approximate estimation of chlorine in the urine (which must be free from 

 protein) is made by strongly acidifying with nitric acid and then adding to it, 

 drop by drop, a concentrated silver-nitrate solution (1:8). In a normal quantity 

 of chlorides the drop sinks to the bottom as a rather compact cheesy lump. In 

 diminished quantity of chlorides the precipitate is less compact and coherent, 

 and in the presence of very little chlorine a fine white precipitate or only a 

 cloudiness or opalescence is obtained. 



Phosphates. Phosphoric acid occurs in acid urines partly as dihydro- 

 gen, MH2PO4, and partly as monohydrogen, M2HP04, phosphates, 

 both of which may be found in acid urines at the same time. The 

 proportion of these may vary considerably; acid urines contain chiefly 

 dihydrogen phosphate and in many cases the urine seems to contain only 

 dihydrogen phosphate and sometimes indeed only a small quantity of phos- 



1 Zeitschr. f. physiol. Chera., 44. 



2 Ekehorn, Hygiea, Stockholm, 1906; Morner, Upsala Lakaref. Forh. (N. F.), 11. 



