646 PHYSIOLOGICAL CHEMISTRY 



PzOs. If stronger than this dilute accordingly and check again by 

 titration. 



Urease. 1 (a) Soy Bean Meal. Grind the soy bean to a powder 

 which will pass through a 2o-mesh sieve. 



(b) Solid Urease Preparation. Digest i part of soy bean meal with 

 5 parts of water at room temperature, with occasional stirring for an 

 hour, and clear the solution by filtration through paper pulp or centri- 

 fugation. Pour this extract slowly, with stirring, into at least 10 volumes 

 of acetone. The acetone dehydrates the enzyme preparation. Filter, 

 dry in vacuum and powder. For standardization procedure see the 

 determination of urea in urine. 



(c) Enzyme Solution. Dissolve 2 grams of urease, prepared as above, 

 together with 0.6 gram of di-potassium-hydrogen phosphate and 0.4 

 gram of mono-potassium-dihydrogen phosphate "in 10 c.c. of water. 

 The solution may be kept under toluene for two weeks, without losing 

 activity. 



(d) Alcoholic Urease Solution. Place 3 grams of permutit in a flask, 

 wash once with 2 per cent acetic acid, then twice with water; add 5 

 grams of fine jack bean meal and 100 c.c. of 30 per cent alcohol. Shake 

 gently but continuously for 10 to 15 minutes and filter. The filtrate 

 contains practically all of the urease and extremely little of other 

 materials. 



Uric Acid Reagents. 2 (a) Silver Lactate Solution. A solution of 

 5 per cent silver lactate in 5 per cent lactic acid. 



(b) Standard Uric Acid Solution. In a 500 c.c. flask dissolve 

 exactly i g. of uric acid in 150 c.c. of water by the help of 0.5 g. lithium 

 carbonate. Dilute to 500 c.c. and mix. Transfer 50 c.c. to a liter 

 flask, add. 500 c.c. of 20 per cent sodium sulphite solution, dilute to 

 volume and mix. Each c.c. of this solution is then equal to o.i mg. of 

 uric acid. Transfer to small bottles (cap. 200 c.c.) and stopper tightly. 

 Thjs standard uric acid solution keeps almost indefinitely in unopened 

 bottles, because the sulphite prevents the spontaneous oxidation of 

 the .uric acid. In used bottles the standard usually remains good for 

 2-3 months. 



(c) Sodium Carbonate Solution. Dissolve 200 grams of anhydrous 

 sodium carbonate in warm water, cool and dilute to i liter. 



(d) Uric Acid Reagent. Introduce into a flask 700 c.c. of water, 

 100 g. of sodium tungstate, and 80 c.c. of phosphoric acid (85 per cent. 

 H 3 P0 4 ). Partly close the mouth of the flask with a funnel and a small 

 watch glass and boil gently for 2 hours. Dilute to i liter. 



1 Determination of urea, pp. 278, 285, and 514. 

 ^Determination of uric acid, p. 281 and p. 530. 



