URINE 557 



Calculate the quantity of sodium chloride and chlorine in the 24-hour urine 

 specimen. 



Interpretation. From 10-15 grams of chlorine, expressed as sodium 

 chloride, are excreted per day, on the average, by normal adults. The 

 amount is, however, closely dependent upon the chloride content of 

 the food ingested. In fasting, the chloride excretion falls rapidly to 

 a very minimal quantity. On high water ingestion it is increased. 

 In pneumonia and certain other acute infectious diseases the excretion 

 of chlorides may be markedly diminished particularly during the 

 periods in which exudates are forming. In convalescence and with 

 resolution of the exudates the chlorine excretion rises again. A de- 

 crease has also been noted in nephritis associated with edema. 



2. Volhard-Harvey Method. 1 Principle. This procedure differs 

 from the Volhard-Arnold method in that the excess of silver nitrate 

 is titrated directly without filtering and hence in the presence of the 

 silver chloride. The procedure is thus more rapid but the exact end 

 point is more difficult to determine. 



Procedure. Introduce 5 c.c. of urine into a small porcelain evaporating 

 dish or casserole and dilute with about 20 c.c. of distilled water. Precipitate 

 the chlorides by the addition of 10 c.c. of standard silver nitrate solution 2 and 

 add 2 c.c. of acidified indicator. 3 Now run in a standard ammonium thiocyanate 

 solution 4 from a burette until a faint red-brown tint is visible throughout the 

 mixture. This point may be determined readily by permitting the precipitate 

 to settle somewhat. Calculate the sodium chloride value as indicated below. 



(If a red tint is produced when the first drop of thiocyanate is added an addi- 

 tional 10 c.c. of the standard silver nitrate solution must be introduced. The 

 titration should then proceed as above described and proper allowance made in 

 the calculation for the extra volume of silver nitrate employed.) 



Calculation. Since 2 c.c. of the ammonium thiocyanate solution is equivalent 

 to i c.c. of the silver nitrate solution, divide the burette reading by 2 and sub- 

 tract the quotient from 10 c.c., the quantity of silver nitrate solution taken. 

 This value is the number of cubic centimeters of silver nitrate solution actually 



1 Harvey: Archives of Internal Medicine, 6, 12, 1910. 



2 See p. 556. 



3 This is prepared as follows: To 30 c.c. of distilled water add 70 c.c. of 33 per cent 

 nitric acid (sp. gr. 1.2) and dissolve 100 grams of crystalline ferric ammonium sulphate in 

 this dilute acid solution. Filter and use the filtrate which is a saturated solution of the iron 

 salt. This single reagent takes the place of the nitric acid and ferric alum as used in Vol- 

 hard-Arnold method, and insures the use of the proper quantity of acid. 



4 This is a solution of ammonium thiocyanate of such a strength that 2 c.c. is equivalent 

 to i c.c. of the silver nitrate solution. First make a concentrated solution by dissolving 13 

 grams in i liter of water. To determine the requisite dilution to make such a solution that 

 2 c.c. shall be equivalent to i c.c. of the silver nitrate solution proceed as follows: Introduce 

 10 c.c. of the silver nitrate solution into a small porcelain evaporating dish or casserole, add 

 3050 c.c. of distilled water, 2 c.c. of the acid indicator and titrate as described above with 

 the ammonium thiocyanate solution. The total volume of the concentrated thiocyanate 

 solution excluding that used in this titration is divided by 10, and the result multiplied by 

 the difference between this burette reading and 20 c.c. This will give the volume of dis- 

 tilled water which must be added to the concentrated thiocyanate solution to render 2 c.c. 

 equivalent to i c.c. of the silver nitrate solution. 



