April, 1918 



C. U. C. P. ALUMNI JOURNAL 



61 



The hemoglobin decomposes the hy- 

 drogen peroxide (catalysis) and the lib- 

 erated oxygen oxidizes the benzidine. 

 The sensitiveness of the benzidine reac- 

 tion is greater when applied to aqueous 

 solutions than when applied to the urine. 

 According to Ascarelli the benzidine re- 

 action serves to detect blood when pres- 

 ent in a solution of i .-3,000,000. Walter 

 has also shown the test to be very deli- 

 cate, and claims it to be more satisfac- 

 tory than the guaiac test. Lyle, Curt- 

 man and Marshall have investigated the 

 benzidine reaction very carefully. They 

 suggest a new procedure in preparing the 

 reagent and in conducting the test : Into 

 a perfectly clean dry test-tube introduce 

 1.4 mils benzidine solution, add 0.2 mils 

 of water or glacial acetic acid, then i mil 

 of the fluid to be tested and finally 0.4 

 mils of 3 per cent, hydrogen dioxide. 

 Note the appearance of a blue color, 

 which reaches its maximum in five to 

 six minutes. 



The acetic acid keeps the benzidine in 

 solution. An excess diminishes the deli- 

 cacy of the reagent. 



Hydrogen dioxide supplies oxygen for 

 the reaction and also bleaches the blue 

 color. An excess of dioxide interferes 

 with the reaction by destroying the 

 catalytic power of the blood and by re- 

 acting with the benzidine itself, with the 

 formation of products which appear to 

 have an inhibitory action. It is very es- 

 sential that the hydrogen dioxide be 

 added last. 



The benzidine solution should be di- 

 lute. Such solutions are exceedingly sen- 

 sitive and permit the detection of blood 

 when present in ratio i :5,ooo,ooo. 



Benzidine solution may be prepared as 

 follows : Place 4.33 mils of glacial acetic 

 acid in a small Erlenmeyer flask, warm 

 to 50° and add 0.5 gramme of benzidine. 

 Heat the flask for eight to ten minutes in 

 water at 50°. To the resultant solution 

 add 19 mils of distilled water. This so- 

 lution may be kept for several days with- 

 out deterioration. 



Whitney's Reagent.— T. B. S., New 

 York, asks for the formula for Whitney's 

 reagent for glucose in urine. In the 

 Druggists Circular 58.1914,407 we find 

 the following formula said to be very 

 similar to that of the proprietary article. 



Solution A. 



Ammonium sulphate 1.2 grammes 



Copper sulphate 2.6 grammes 



Water 50.0 mils 



Solution B. 

 Potassium hydroxide .... 20.0 grammes 

 Water -. 50.0 mils 



Dissolve, then add 



Glycerin 50.0 mils 



Ammonia water (28%) 300.0 mils 



Before using, add Solution A to Solu- 

 tion B and make up with water to 500 

 mils. 



In using this solution, a fluidrachm of 

 the solution is heated to boiling in a test 

 tube and to the boiling fluid the urine is 

 added drop by drop until the blue color 

 of the mixture is discharged. It has 

 been arbitrarily determined that when 3 

 minims of urine discharge the color, glu- 

 cose is present in the proportion of 10 

 grains to the fluid ounce, that 5 minims 

 represent 5 grains to the fluid ounce ; that 

 9 minims represent 2 grains to the fluid 

 ounce; and that 17 minims represent I 

 grain of sugar to the fluid ounce. 



