464 APPENDIX 



the closed portion of the U tube is filled with the hypobromite solution, and the urine 

 introduced by allowing it to run in from the side tube by opening the glass cock 

 arranged for that purpose. After the gas has risen and the instrument has stood 

 for a short time the readings may be made in grams to the liter, or in percentage. 



This urea determination is only a rough clinical one. 



Urea Determination by Urease Method. Put i or 2 c.c. of toluol into each of 

 two 200 c.c. Erlenmeyer flasks; to one, add exactly 5 c.c. of a specimen and TOO c.c. 

 of distilled water; to the other, one Urease-Dunning tablet, crushed and dissolved 

 in about 5 c.c. of water, using a small glass mortar. Rinse the mortar with several 

 portions of distilled water until about 100 c.c. have been introduced into second flask 

 and then add exactly 5 c.c. of the urine specimen. Stopper both flasks with cork 

 and agitate contents. If time is not a consideration, allow flasks to stand at room 

 temperature, at least eight hours, or use two tablets and digest at 4oC. for one hour. 

 Rapid determination may be made by using but i c.c. of urine, two tablets and 100 

 c.c. of distilled water and digest between 40 and 50 C. for thirty minutes only. 



After the elapse of proper time, titrate the two solutions to a distinct pink color 

 with N/io HC1 and methyl orange. The amount of HC1 required to neutralize 

 the urease-treated specimen, less the amount required for the control, will give the 

 urea content, estimated upon its equivalent in ammonium carbonate. 



The controls of a large number of determinations made at one time may be ti- 

 trated, as to existing alkalinity, with N/io HC1 and methyl orange, one after another, 

 in the same flask, at the time the portions to be examined for urea are prepared in 

 separate flasks. In such cases, a sufficient number of Urease-Dunning tablets, 

 for all, may be rubbed up in a mortar with a measured quantity of distilled water 

 and an aliquot portion, with 100 c.c. of distilled water, added to each of the separate 

 specimens treated. See urease method for blood. 



Gerhardt's Test for Diacetic Acid 



Add a few drops of ferric chloride solution to 10 to 50 c.c. of urine as long as a 

 precipitate continues to form. Then filter and to the filtrate add more ferric chloride 

 solution. A bordeaux red color shows diacetic acid. The test is sensitive. As a 

 control to show that the color is not due to drug elimination (antipyrine, salicylates, 

 etc.) boil a specimen which gave the test for three to five minutes. If the color was 

 due to drugs it will be obtained with a boiled sample while such treatment drives off 

 the diacetic acid. In Hurtley's test add 2.5 c.c. HC1 and i c.c. of i% sol. of sod. 

 nitrate to 10 c.c. urine. Shake and allow to stand two minutes. Now add 15 c.c. 

 strong ammonia followed by 5 c.c. of 10% sol. ferrous sulphate. The slow produc- 

 tion of a violet color shows positive test (two hours). Shows i part aceto-acetic 

 acid in 50,000. 



If the urine shows a well-marked Gerhardt reaction it is well to test for /3-oxy- 

 butyric acid. 



The following modification of Lange's test by Hart is a satisfactory one, The 

 principle involved is the removal of acetone and diacetic acid by heat, then oxidizing 

 /3-oxybutyric acid to acetone with hydrogen peroxide and then testing for acetone. 



Method: Take 20 c.c. of urine, dilute with an equal amount of water and add a 

 few drops of acetic acid. Next boil in a beaker until the original amount of diluted 



