168 THE URINE. 



the crisis, then an increase. In chronic diseases the amount 

 of chlorin gives some indication of the digestive power, 

 6 to 10 grammes per day being normal, and less than 5 

 grammes daily showing weakness of digestion, providing 

 that an excessive amount has not been removed by other 

 means, like serous exudations or diarrhoeic discharges. An 

 excessive excretion of chlorin (15 to 20 grammes daily) 

 is found in diabetes insipidus. In dropsical conditions it 

 is a favorable sign, showing the absorption of the fluid. 

 The quantity of chlorin can be determined by ascer- 

 taining how much silver nitrate is required to precipitate 

 it. 



NaCl + AgN0 3 = AgCl + NaN0 3 . 



58.4 parts 170 parts 



To ascertain when the chlorin has all united with the 

 silver a little yellow potassium chromate is added. The 

 silver forms first a white silver chlorid, and when the chlo- 

 rin has been precipitated it forms the red silver chromate. 



364. Acidify a portion of urine in a test-tube with 

 nitric acid and add a little silver nitrate. A white precipi- 

 tate which turns dark in the sunlight indicates the pres- 

 ence of chlorids. 



365. DETERMINATION OF QUANTITY or CHLORIN IN 

 URINE. For clinical purposes the following method is suf- 

 ficiently accurate : Measure with a pipette 10 cubic centi- 

 meters of urine and dilute with about 100 cubic centi- 

 meters of water. Add a few drops of yellow potassium 

 chromate solution ; then allow to flow into it from a burette 

 a solution which contains 17.000 grammes of fused silver 

 nitrate in a liter. As soon as the color of the precipitate 

 changes from white to reddish, read off the volume of silver 

 solution which has been used. Each cubic centimeter of 



