UKIC ACID, CREATINE, CREATININE, AND ALLANTOIN 239 



Make up to 100 ml. and store in a brown bottle in a refrigerator. 



Hypochlorite Solution. Dissolve as much as possible of 25 g. of 

 ground and sifted calcium hypochlorite in 300 ml. hot water. With 

 stirring, add 135 ml. 20% potassium carbonate soln. which had 

 been boiled to drive out ammonia. Heat briefly to about 90°, cool, 

 and dilute to 500 ml. Filter a little of the soln. and test for calcium 

 ion by adding some of the potassium carbonate soln. and heating 

 in boiling water a few min. In the absence of calcium ion the 

 solution remains crystal clear. If the test is positive, add more 

 carbonate until a negative test is obtained. Filter the final soln. 

 and store in small brown bottles in a refrigerator. This soln. 

 should be water clear and contain 1.30-1.40% free chlorine. Test 

 for free chlorine by adding 10 ml. water, 2 ml. 5% potassium 

 iodide, and 1 ml. glacial acetic acid to 2.00 ml. of the hypochlorite 

 solution. Titrate with 0.100 A^ thiosulfate; 7.5-8.0 ml. should be 

 required. Occasionally retest the solution. The soln. may also be 

 prepared from Clorox (page 58), 



0.003 M Manganous Chloride or Sulfate. 



PROCEDURE 



1. Place 1.5 ml. sample in neutral or acid solution not stronger 

 than 0.01-0.02 A^ (containing 0.5-6.0 /xg. ammonia nitrogen) in a 

 colorimeter tube, cooled by an ice bath. Add 1 drop manganous salt 

 soln., 1 ml. cold alkaline phenol reagent, and 0.5 ml. cold hypochlorite 

 solution. Mix by gentle rotation and place at once in a boiling water 

 bath for about 5 min. 



2. Cool, dilute to a convenient volume such as 6 or 10 ml., and 

 measure the color intensity with light of about 625 m/x. 



URIC ACID, CREATINE, CREATININE, AND ALLANTOIN 



Borsook (1935) reported colorimetric methods for uric acid, 

 creatine, creatinine, and allantoin which were modifications of pro- 

 cedures already in use, but which are in the_ category of micro 

 methods, even though no special micro equipment is required. The 

 colorimetric measurements were carried out spectrophotometrically 

 in cuvettes taking 3.0-3.5 ml. With the present availability of micro- 

 cuvettes, these methods could be adapted to the analysis of much 

 smaller quantities of the substances by substituting smaller test 

 tubes for the 125 X 9 mm. (inside dimensions) tubes used. 



