THE AROMATIC CONSTITUENTS OF THE URINE. 249 



paracresol, the normal urine of man is said also to contain minute 

 amounts of meta- and ortho-cresols. The total elimination of 

 cresols and phenols, however, normally corresponds to only about 

 0.03 gramme in the twenty-four hours. 



Urine which contains much hydroquinon or pynocatechill gradually / 

 assumes a dark-brown color on standing if the reaction is alkaline, / 

 and it is noted that this change in color begins in the upper layers j 

 and gradually extends downward. Ultimately the urine becomes 

 almost black. This change is referable to oxidation of the clioxy- 

 ben/ols, but of the resulting compounds nothing is known. Urines 

 of this character are mostly observed in poisoning with carbolic acid, 

 following the administration of benzol, of phenol sulphates, etc. 



To demonstrate the presence of phenol or of paracresol, 1000 

 c.c. of urine are treated with 70 c.c. of concentrated hydrochloric 

 acid, and distilled until about one- fourth of the total amount 

 has passed over. The conjugate sulphates are thus decomposed, 

 and phenol and cresol are found in the distillate. Their presence 

 can here be demonstrated by testing with Million's reagent or by 

 adding bromine-water, when tribromophenol crystallizes out on 

 standing. If much phenol is present, it may further be possible 

 to obtain a positive reaction with ferric chloride solution if this is 

 added drop by drop in very dilute solution. Hydroquinon and 

 pyrocatechin remain in the acid solution. To demonstrate their pres- 

 ence, the solution is evaporated to about 100 c.c., and on cooling is 

 extracted with an equal volume of ether. Hydroquinon and pyro- 

 catechin together with the aromatic oxy-acids are thus removed. 

 On adding a dilute solution of sodium carbonate to the ethereal solu- 

 tion the aromatic oxy-acids are transformed into the corresponding 

 sodium salts. The ethereal extract, which now contains only the 

 dioxy-benzols, is evaporated to dryness ; the residue is dissolved in 

 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 2 , results, and may be recognized by its penetrating odor. 



Quantitative Estimation. METHOD OF KOSSLER AND PENNY, 

 MODIFIED BY XEUBERG. 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 



