106 LABORATORY WORK IN PHYSIOLOGICAL CHEMISTRY. 



Quantitative Estimation. 



To 25 c.c. of urine in a flask add 15-20 grms. of powdered 

 potassium oxalate and two drops of phenolphthalein. Allow 

 the oxalate to partly dissolve by shaking and titrate the 



mixture immediately with ^ NaOH until the first faint 



pink coloration is discernible. The acidity in this case is 



N 

 expressed in terms of j~ acid for 100 c.c. of urine. 



CHLORIDES. 



The quantity of chlorine excreted in the urine during the 

 24 hours is subject to great variations. On a mixed diet it 

 usually amounts to from 10 to 15 grms., calculated as NaCl. 

 Under normal conditions the quantity eliminated is depend- 

 ent upon the quantity of chlorine and water ingested; but 

 in pathological states, such as the formation and subsequent 

 absorption of exudates, it is respectively markedly decreased 

 and then increased. In starvation the amount becomes 

 minimal. 



Quantitative Estimation. 



The principle of the method is the following: 

 To the urine is added an excess of AgN0 3 over and above 

 what is necessary to precipitate all the chlorides present. 

 The excess of Ag is then determined by means of a sulpho- 

 cyanide solution, using iron alum as an indicator. 

 Reagents necessary: 



1. A AgN0 3 solution, each c.c. of which precipitates 0.01 

 grm. NaCl (29.075 grms. AgNO 3 in a liter). 



2. A saturated solution of iron alum. 



3. Chlorine-free HN0 3 of a specific gravity 1.2. 



