466 



PEACTICAL PHYSIOLOGY 



creatinin to form a salt of known composition. By collecting this salt 

 on a weighed filter, or better, by estimating its nitrogen, the amount of 

 creatinin which it contains can be determined. 



Solutions necessary. 1. Alcoholic zinc chloride. A concentrated 

 watery solution of zinc chloride is poured into 90 per cent, alcohol 

 until the specific gravity of the latter rises to 1-20. 



2. Milk of lime prepared by shaking quicklime with water. 



3. 5 per cent calcium chloride solution. 



Determination. 480 c.c. urine are mixed with milk of lime until 

 faintly alkaline in reaction, and then with calcium chloride solution 

 until no further precipitation of phosphates results. The volume is 





FIG. 273. Creatinin zinc chloride, x 300. 



made up to 600 c.c. by adding water, and the solution is filtered. 500 

 c.c. of the filtrate are rendered slightly acid by the careful addition of 

 10 per cent, acetic acid, then placed in a large evaporating dish, and 

 evaporated, at first over a flame, but afterwards on a water-bath, until the 

 volume is about 40 c.c. The resulting syrup is then transferred to a 

 stoppered measuring cylinder of at least 200 c.c. capacity, the last trace 

 of the fluid being washed into the cylinder by means of absolute 

 alcohol. The solution is made up to 200 c.c. with absolute alcohol, and 

 is then allowed to stand 24 hours so that all the sodium chloride 

 may become precipitated. The solution is filtered through a dry filter 

 paper, and of the filtrate two samples of 80 c.c. each are measured into 

 small beakers, and mixed with 1 c.c. of alcoholic zinc chloride. The 

 beakers are covered with a ground glass plate and placed in a cool 

 place for at least three days, the contents being briskly stirred at 

 least once a day. The creatinin zinc chloride separates out as a dirty 



