422 PHYSIOLOGICAL CHEMISTRY. 



to dissolve freshly-precipitated HgO. A mercuric-chloride solution 

 is precipitated by alcoholic caustic potash. To this add the liquid 

 to be tested for acetone, shake well and filter. In the presence of 

 acetone the filtrate contains mercury, which may be detected by 

 ammonium sulphide. This test has about the same delicacy as 

 GUNNING'S test. 



LEGAI/S Sodium-nitroprusside Test. If an acetone solution is 

 treated with a few drops of a freshly-prepared sodium-nitroprusside 

 solution and then with caustic-potash or soda solution, the liquid 

 is colored ruby-red. Creatinin gives the same color ; but if we sat- 

 urate with acetic acid, the color becomes carmine or purplish red in 

 the presence of acetone, but yellow and then gradually green and 

 blue in the presence of creatinin. If we use ammonia instead of 

 the caustic alkali (LE NOBEL), the reaction takes place with acetone 

 but not with creatinin. LEGAI/S test indicates even 0.1 milligrm. 

 acetone. 



PENZOLDT'S indigo test depends on the fact that orthonitroben- 

 zaldehyde in alkaline solution with acetone yields indigo. A warm 

 saturated and then cooled solution of the aldehyde is treated with 

 the liquid to be tested for acetone and then with caustic soda. 

 In the presence of acetone the liquid first becomes yellow, then 

 green, and lastly indigo separates; and this may be dissolved with 

 a blue color by shaking with chloroform. 1.6 milligrms. acetone 

 can be detected by this test. 



Aceto-acetic Acid, or DIACETIC ACID, 4 H 6 3 or C 2 H 3 O.CH 2 . 

 COOH. This acid is a colorless, strongly-acid liquid which mixes 

 with water, alcohol, and ether in all proportions. On heating to 

 boiling with water, and especially with acids, this acid decomposes 

 into carbon dioxide and acetone, and therefore gives the above- 

 mentioned reactions for acetone. It differs from acetone in that it 

 gives a violet-red or brownish-red color with a dilute ferric-chloride 

 solution. This color decreases even at the ordinary temperature 

 within 24 hours, and more quickly on boiling. It differs in this 

 from phenol, salicylic acid, acetic acid, or sulphocyanides. 



Detection of Acetone and Aceto-acetic Acid in the urine. Before 

 testing for aceto-acetic acid test for acetone, and as this acid gradu- 

 ally decomposes on allowing the urine to stand, the urine must be 

 as fresh as possible. In the presence of aceto-acetic acid the urine 



