282 THE URINE. 



monia. The mixture is shaken until it assumes a brick-red color. 

 From 10 drops to 2 c.c., according to the amount of diacetic 

 acid present, are treated with 15-20 c.c. of concentrated hydro- 

 chloric acid (sp. gr. 1.19), 3 c.c. of chloroform, and 2-4 drops 

 of an aqueous solution of ferric chloride. The tube is closed with 

 a. cork and gently agitated (so as to avoid emulsifi cation), when after 

 one-half to one minute a beautiful and very characteristic violet 

 tinge results if diacetic acid is present. In its absence the color is 

 yellowish or slightly reddish. The violet color persists for a long 

 time. Salicylic acid, phenacetin, antipyrin, phenol, and other drugs 

 are without disturbing influence upon the reaction. 



Allard states that both Arnold's test and that of Lipliawski give 

 a positive result also with acetone, when this is present to the extent 

 of more than 1 per cent. 



GERHARDT'S TEST. In its original form this test also reacts 

 with the common antipyretics, and it is hence necessary to isolate 

 the diacetic acid to a certain degree. To this end, a few cubic cen- 

 timeters of the urine are strongly acidified with sulphuric acid 

 and extracted with ether, which takes up the acid. The extract 

 is then shaken with a few cubic centimeters of a dilute solution of 

 the chloride of iron, when in the presence of diacetic acid the aqueous 

 layer assumes a violet or Bordeaux-red color. This, however, is 

 not permanent, and soon fades on boiling the solution. 



Acetone. 



The origin of acetone has been discussed above (see Oxybutyric 

 Acid). 



Traces varying between 0.008 and 0.027 gramme in the twenty- 

 four hours are normally found in the urine. 



Acetonuria is essentially a pathological phenomenon, and is ob- 

 served in most pronounced form in severe cases of diabetes, in 

 which, as I have stated, it is frequently met with in association 

 with /9-oxybutyric acid and diacetic acid. Like diacetic acid, how- 

 ever, it may occur in the absence of oxybutyric acid, and in the 

 milder forms of diabetes, as also under normal conditions it may be 

 present alone. 



Tests. Should diacetic acid be demonstrated in the urine, the 

 simultaneous presence of acetone may be directly inferred. If this 

 is not the case, it is best to distill from 250 to 500 c.c. of the urine, 

 after the addition of a small amount of phosphoric acid, and to 

 apply the following tests to the first 15 or 30 c.c. of the distillate 

 that has passed over. 



LEGAL' s TEST. A few cubic centimeters of the distillate are 

 rendered strongly alkaline with caustic soda solution and then treated 

 with several drops of a freshly prepared, concentrated solution of 

 sodium nitroprusside. In the presence of acetone a red color devel- 

 ops, which rapidly fades, however, but is replaced by a beautiful 



