428 A MANUAL OF PHYSIOLOGY 



Or, instead of being estimated by weighing, the uric acid crystals 

 may, after having been washed with the cold distilled water as 

 described, till free from chlorides, be washed again with hot water 

 off the filter (which need not in this case be a weighed one) into a 

 capsule. The capsule is filled up with distilled water, i c.c. of 10 

 per cent, sodium carbonate solution added, and the contents heated 

 to boiling to dissolve the uric acid. The solution is allowed to cool, 

 and then emptied into an Erlenmeyer's flask with a mark roughly 

 corresponding to 100 c.c. The solution is made up to 100 c.c. with 

 distilled water. A burette is filled with standard potassium per- 

 manganate solution (a twentieth-normal solution made by dissolving 

 1*581 grammes of the permanganate in a litre of water). 20 c.c. of 

 strong sulphuric acid are poured into the flask, which is then shaken. 

 The permanganate is now run in with constant shaking of the flask. 

 At first the pink colour produced where the drops of permanganate 

 fall into the liquid disappears at once without spreading through the 

 liquid. When a certain amount has been run in, however, the whole 

 liquid becomes pink, although the colour soon disappears. This 

 indicates that enough of the permanganate has been added. Each 

 c.c. of the permanganate used is equivalent to 0*00375 gramme uric 

 acid. One milligramme must be added, as before, to the result for 

 each 15 c.c. of the mother liquor from which the uric acid crystals 

 were deposited. 



10. Kreatinin. Qualitatively ', kreatinin may be recognised in very 

 small amounts by Weyfs test. A few drops of a dilute solution of 

 sodium nitro-prusside are added to urine, and then dilute sodium 

 hydrate drop by drop. A ruby-red colour appears, which soon turns 

 yellow. If the urine is now strongly acidified with acetic acid and 

 heated, it becomes first greenish and then blue. Enough acid must 

 be added to more than neutralize the alkali. 



Kreatinin forms crystalline compounds with various acids and salts. 

 One of the best known of these is kreatinin-zinc-chloride, formed 

 on the addition of zinc chloride to an alcoholic or watery solution of 

 kreatinin, often in the shape of beautiful thick-set rosettes of needles. 

 Neubauer has made this reaction the basis of a method for the 

 quantitative estimation of kreatinin (Fig 120, p. 389). 



11. Hippuric Acid. From horse's or cow's urine hippuric acid is 

 prepared by evaporating to a small bulk, and adding strong hydro- 

 chloric acid. The crystalline precipitate is washed with cold water, 

 then dissolved in hot water, and filtered hot. Hippuric acid separates 

 out from the filtrate in the cold in the form of long four-sided prisms 

 with pyramidal ends. Heated dry in a test-tube, the crystals melt, 

 and benzoic acid and oily drops of benzonitrile, a substance with a 

 smell like that of oil of bitter almonds, are formed. 



ABNORMAL SUBSTANCES IN URINE. 



12. Proteids. (i) Qualitative Tests.(d) Boil and add a few 

 drops of nitric acid. A precipitate on boiling, increased or not 

 affected by the acid, shows the presence of coagulable proteids 



