THE AROMATIC OXY-ACIDS. 267 



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 centim- 

 eters 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. Traces of acetone, varying between 0.008 and 0.027 

 gramme in the twenty-four hours are normally found in the urine. 

 Larger quantities are met with if the carbohydrates are withdrawn 

 from the diet, and in such cases from 0.2 to 0.7 gramme may be 

 excreted after the sixth day. If then carbohydrates are again 

 ingested, the elimination of the acetone rapidly reaches its origi- 

 nal figure ; the ingestion of fats, on the other hand, is without 

 effect in this respect. Acetonuria, however, is essentially a patho- 

 logical phenomonen, and is observed in its most pronounced form 

 in severe cases of diabetes, in which, as I have stated, it is fre- 

 quently met with in association with /3-oxybutyric acid and diacetic 

 acid. Like diacetic acid, however, 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. But while its import is 

 generally the same as that of its immediate antecedents, it appears 

 that it may originate also in the gastrointestinal tract as the result 

 of some abnormal form of albuminous putrefaction, and it is possi- 

 ble, indeed, that the so-called asthma-acetonicum may be of this 

 origin. That small amounts are formed also during the hydro- 

 lytic decomposition of the albumins with boiling mineral acids or 

 the caustic alkalies, has been mentioned, v. Jaksch, further, has 

 shown that acetone may be formed as a by-product during the 

 process of lactic acid fermentation, and it has been suggested 

 that the small amounts which are normally met with in the urine 

 may originate in this manner. At present, however, we are not 

 in a position to speak authoritatively of the origin of these normal 

 traces, and, pathologically at least, we can thus far acknowledge 

 but one source of the acetone, viz., the albumins of the body 

 tissues, and secondarily perhaps the circulating albumins. 



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 

 treated with several drops of a freshly prepared, concentrated solu- 

 tion of sodium nitroprusside, and a small amount of a dilute solti- 



