720 URINE. 



mixed diet islO-15 grams of NaCl per twenty-four hours. The quantity of 

 common salt in the urine depends chiefly upon the amount of salt in the 

 food, with which the elimination of chlorine increases and decreases. The 

 free drinking of water also increases the elimination of chlorine, which is 

 greater during activity than during rest (at night). Certain organic 

 chlorine combinations, such as chloroform, may increase the elimination 

 of inorganic chlorides by the urine (ZELLER, KAST *) . 



In diarrhoea, in quick formation of large transudates and exudates, 

 also in specially marked cases of acute febrile diseases at the time of the 

 crisis, the elimination of NaCl is materially decreased. The excretion of 

 chlorine may vary considerably in disease, but still the NaCl taken with 

 the food has here, as in physiological conditions, a great influence on the 

 NaCl excretion. 2 



The quantitative estimation of chlorine in the urine is most simply per- 

 formed by titration with silver-nitrate solution. The urine must not 

 contain 'either proteid (which if present must be removed by coagulation) 

 or iodine or bromine compounds. 



In the presence of bromides or iodides evaporate a measured quantity of the 

 urine to dryness, fuse the residue with saltpeter and soda, dissolve the fused 

 mass in water, and remove the iodine or bromine by the addition of dilute sul- 

 phuric acid and some nitrite, and thoroughly shake with carbon disulphide. 

 The liquid thus obtained may now be titrated with silver nitrate according to 

 VOLHARD'S method. The quantity of bromide or iodide is calculated as the 

 difference between the quantity of silver-nitrate solution used for the titration 

 of the solution of the fused mass and the quantity used for the corresponding 

 volume of the original urine. 



The otherwise excellent titration method of MOHR, according to which 

 we titrate with silver nitrate in neutral liquids, using neutral potassium 

 chromate as an indicate^ cannot be used directly on the urine in careful 

 work. Organic urinary constituents are also precipitated by the silver 

 salt, and the results are therefore somewhat high for the chlorine. If this 

 method is to be employed, the organic urinary constituents must first be 

 destroyed. For this purpose evaporate to dryness 5-10 cc. of the urine, 

 after the addition of 1 gram of chlorine-free soda and 1-2 grams chlorine- 

 free saltpeter, and carefully fuse. The mass is dissolved in water, acidified 

 faintly with nitric acid, and then neutralized exactly with pure calcium 

 carbonate. This neutral solution is used for the titration. 



The silver-nitrate solution may be a N/10 one. It is often made of 

 such a strength that each cubic centimeter corresponds to 0.006 gram 

 Cl or 0.01 gram NaCl. This last-mentioned solution contains 29.075 

 grams of AgNO 3 in 1 liter. 



1 Zeller, Zeitschr. f. physiol. Chem., 8; Kast, ibid., 11; Vitali, Chem. Centralbl., 

 1899, 2. 



2 On the elimination of chlorine in disease, see Albu and Neuberg, Physiol. u. Pathol. 

 des Mineralstoffwechsels, Berlin, 1906. 



