CREATININ. URIC ACID. 167 



N 



From the quantity of -- H 2 SO 4 originally measured into 



the receiver (C) subtract the cc NaOH used to neutralise 



the uncombined acid, and multiply the difference by 0*0014, 

 which will give the grammes of nitrogen contained in 10 cc 

 of urine. The percentage will be obtained by multiplying 

 by 10. 



Creatinin. l g or over in 24 hours. Is derived from the 19 

 fleshy part of food. It comes next in importance quantita- 

 tively after urea. Is freely soluble in water and has an 

 alkaline reaction. 



1. It reduces copper oxide, hence may be taken for small 



quantities of sugar. The reduced copper collects at 

 the bottom of the tube. Try normal urine. 



2. WeyVs reaction. Add to a quarter tube of urine a very 



dilute solution of sodium nitroprusside, and then drop 

 by drop a dilute solution of NaOH, a ruby red colour 

 appears which lasts only a few minutes and passes 

 into a clear straw colour. Add some acetic acid, the 

 ruby colour rapidly decolourises. Compare with the 

 reaction for acetone. 



Uric Acid, 0-5 a little more in 24 hours. 

 Properties : 



1. Its solubility is very low 1 to 14,000 in cold, and 1 to 



1,800 in boiling water. Most important from a clinical 

 point of view, as consequently it readily appears as a 

 sediment in the urine. 



2. It crystallises ordinarily in urine in the form of whet- 



stone - shaped crystals, coloured brownish - red by 

 entangled urinary pigment (uroerythrin). When crystal- 

 lised pure it forms rhombic prisms. 



