URINE: QUANTITATIVE ANALYSIS. 397 



of the argentic nitrate solution is present, continually shaking the 

 mixture during the addition of the standard solution. Allow the 

 flask to stand 10 minutes, then fill it to the 100 c.c. graduation 

 with distilled water and thoroughly mix the contents. Now filter 

 the mixture through a dry filter paper, collect 50 c.c. of the filtrate 

 and titrate it with standardized ammonium thiocyanate solution. 1 

 The first permanent tinge of brown indicates the end-point. Take 

 the burette reading and compute the weight of sodium chloride in 

 the 10 c.c. of urine used. 



Calculation. The number of cubic centimeters of ammonium 

 thiocyanate solution used indicates the excess of standard argentic 

 nitrate solution in the 50 c.c. of filtrate titrated. Multiply this 

 reading .by 2, inasmuch as only one-half of the filtrate was employed, 

 and subtract this product from the number of cubic centimeters of 

 argentic nitrate (20 c.c.) originally used, in order to obtain the 

 actual number of cubic centimeters of argentic nitrate utilized in 

 the precipitation of the chlorides in the 10 c.c. of urine employed. 



To obtain the weight in grams, of the sodium chloride in the 

 10 c.c. of urine used multiply the number of cubic centimeters of 

 the standard argentic nitrate solution, actually utilized in the pre- 

 cipitation, by o.oio. If it is desired to express the result in per- 

 centage of sodium chloride move the decimal point one place to the 

 right. 



In a similar manner the weight, or percentage of chlorine may 

 be computed using the factor 0.006 as explained in Mohr's method, 

 page 396. 



Calculate the quantity of sodium chloride and chlorine in the 

 twenty-four hour urine specimen. 



XIV. Acetone and Diacetic Acid. 



i. Folin-Hart Method. This method serves the same purpose 

 as the Messinger-Huppert Method, i. e., the determination of both 



1 This solution is made of such a strength that i c.c. of it is equal to i c.c. of 

 the standard argentic nitrate solution used. To prepare the solution dissolve 

 12.9 grams of ammonium thiocyanate, NJrUSCN, in a little less than a liter 

 of water. In a small flask place 20 c.c. of the standard argentic nitrate solution, 

 5 c.c. of the ferric alum solution and 4 c.c. of nitric acid (sp. gr. 1.2), add water 

 to make the total volume 100 c.c. and thoroughly mix the contents of the flask. 

 Now run in the ammonium thiocyanate solution from a burette until a 

 permanent brown tinge is produced. This is the end-reaction and indicates that 

 the last trace of argentic nitrate has been precipitated. Take the burette reading 

 and calculate the amount of water necessary to use in diluting the ammonium 

 thiocyanate in order that 10 c.c. of this solution may be exactly equal to 

 TO c.c. of the argentic nitrate solution. Make this dilution and titrate again to 

 be certain that the solution is of the proper strength. 



