THE AROMATIC CONSTITUENTS OF THE URINE. 263 



a little water and examined as follows : one portion is treated drop 

 by drop with a dilute solution of ferric chloride, when in the pres- 

 ence of pyrocatechin a green color develops, which turns to violet 

 upon the addition of a small amount of tartaric acid and ammonia. 

 The remainder of the solution is precipitated with lead acetate and 

 filtered. The filtrate contains the hydroquinon, while the pyro- 

 catechin is in the precipitate. The hydroquinon can then be isolated 

 by acidifying and extracting with ether, when the substance crys- 

 tallizes out on evaporation. It is dissolved in a little water, and 

 treated drop by drop with the dilute iron solution. Quinon, 

 C 6 H 4 O.,, results, and may be recognized by its penetrating odor. 



Quantitative Estimation. METHOD OF KOSSLER AND PENNY, 

 MODIFIED BY NsuBERG. This method is based upon the precipi- 

 tation of phenol and paracresol, by means of iodine, as tri-iodo- 

 phenol. From the amount of iodine which is thus used the corre- 

 sponding amount of monoxy-benzols can be calculated, and is 

 expressed either in terms of phenol or cresol, as the method does 

 not indicate the separate amount of the individual bodies that are 

 present. The reaction which takes place may be represented by 

 the equation : 



C 6 H 5 .OH + 61 = C 6 H 2 .I 3 OH + SHI. 



Five hundred c.c. of urine are rendered feebly alkaline and 

 evaporated to about 100 c.c. Any acetone which may have been 

 present is thus removed. The residual fluid is acidified with sul- 

 phuric acid, so as to contain 5 per cent, of the original volume, and 

 is then repeatedly distilled. The individual portions thus obtained 

 are shaken with calcium carbonate until the acid reaction has dis- 

 appeared, so as to remove any nitrous or formic acid that may be 

 present. The fluid is now again distilled, and the distillate treated 

 with a solution of 1 gramme of caustic soda and 6 grammes of lead 

 acetate in substance. The mixture is kept on a boiling water-bath 

 for about fifteen minutes. A portion of the lead oxide is thus dis- 

 solved by the phenol to form basic phenolates, while any aldehydes 

 or ketones that may have been formed from the small amount of 

 carbohydrates that are present in every urine escape. To remove 

 these entirely, the mixture is heated over a free flame connected with 

 a condenser until a few cubic centimeters of the distillate no longer 

 reduce an alkaline solution of silver nitrate. After five minutes 

 this point is usually reached. The fluid is then acidified with sul- 

 phuric acid as before, and is distilled, water being added from time 

 to time. The distillate is placed in a glass-stoppered bottle, treated 

 with a decinormal solution of sodium hydrate until the reaction is 

 markedly alkaline, and immersed in hot water. To the hot fluid a 

 decinormal solution of iodine is added in an amount which should 

 exceed that of the alkali solution by 15 to 25 c.c. The bottle is 

 now closed at once, shaken, and set aside until cool. The solution 

 is then acidified with dilute sulphuric acid, and the excess of iodine, 



