URINE 343 



of 10% sodic hydrate to each, and let stand for ten minutes. 

 If the alkaline solution is used, add, with a cylinder, 20 c.c. to 

 each flask. At the end of ten minutes dilute to the mark with 

 water and mix. 



Read the standard against itself in the colorimeter at 20 mm. 

 until the correct value (20 mm.) can be obtained. The error in 

 reading should not exceed .2 mm. Rinse the right-hand cup 

 and prism with the unknown, and determine its color in terms 

 of the standard set at 20 mm. Twenty divided by the reading 

 gives the creatinin in milligrams in the quantity of urine taken 

 (1-5 c.c.). 



Calculate the total creatinin. 



Indican. 



By applying the qualitative test for indican, already per- 

 formed by the student, and comparing the color produced with 

 that of Fehlirig's solution as a standard, at least a comparative, 

 if not a quantitative estimation of indican may be made. 



Allantoin. 



For details of the estimation of allantoin consult a larger 

 work. 



Oxalic Acid. 



Oxalic acid may be estimated by the isolation of its calcium 

 salt. 



Chlorides. 



42. Volliard Method. All of the chlorides of the urine are 

 precipitated by adding excess (a known volume) of standard sil- 

 ver nitrate. The excess silver nitrate then is determined by 

 titration with thiocyanate, using a ferric salt as indicator. The 

 thiocyanate is made up so that 1 c.c. exactly corresponds to 1 

 c.c. of the silver nitrate. Silver thiocyanate (white) precipitates 

 first. When all the silver is precipitated, red ferric thiocyanate 

 is formed. 



Into a 100 c.c. volumetric flask measure accurately with a 



