THE DETECTION OF ACETO-ACETIC ACID BY 

 SODIUM NITROPRUSSID AND AMMONIA^ 



V. J. HARDING AND R. F. RUTTAN 

 (Chemical Laboratory, McGill University, Montreal, Canada) 



The use o£ sodium nitroprussid and ammonia, followed by the 

 addition of an acid insufficient in amount to completely neutralize 

 the ammonia, was first suggested by Le Nobel as a method of de- 

 tecting small quantities of acetone. This test is based on the orig- 

 inal test of Legal but, as the two tests differ in result, it is proposed 

 to call the test depending on the use of ammonia, the Le Nobel test, 

 and to reserve the term Legal test exclusively for the action of 

 sodium nitroprussid and potassium (or sodium) hydroxid followed 

 by acidification. 



The two tests differ in the f ollowing points : ( i ) The Le Nobel 

 test gives with acetone a much bluer shade of purple and (2) is an 

 extremely delicate test for aceto-acetic acid. 



The usual way, in clinical work, of applying the Le Nobel test is 

 to first acidify the urine with acetic acid, add a few drops of a dilute 

 Solution of sodium nitroprussid and then overlay the Solution with 

 concentrated aqueous ammonium hydroxid Solution. On applying 

 this test, the authors discovered several anomalies which can be sum- 

 marized as follows : 



(A) Acetone in water and when added to urine, making concen- 

 trations similar to those occurring in cases of acetonuria, gives the 

 test very faintly and only after long standing — ^by no means as dis- 

 tinctly as the natural cases. 



(B) If some samples of urine which give a marked response to 

 the Le Nobel test be distilled with acids, the test given by the dis- 

 tillate (where the acetone is presumably ten to twenty times more 

 concentrated than In the original urine) is very much less marked. 



* Abstract of paper published in the Bio-Chemical Journal, 1912, vi, p. 445 

 (Oct). 



223 



