HOMOGENTISIC ACID. 701 



acid has also been prepared synthetically by BAUMANN and FRANKEL, 

 starting with gentisic aldehyde and by NEUBAUER and FLATOW 1 from 

 o-oxyphenylglyoxylic acid with hydroquinone glyoxylic acid and hydro- 

 quinone glycollic acid as intermediary bodies. 



Homogentisic acid crystallizes with 1 mol. of water in large, trans- 

 parent prismatic crystals, which become non-transparent at the tem- 

 perature of the room with the loss of water of crystallization. They 

 melt at 146.5-147 C., and are soluble in water, alcohol, and ether, 

 but nearly insoluble in chloroform and benzene. Homogentisic acid 

 is optically inactive and non-fermentable. Its watery solution has the 

 properties of so-called alcaptonuric mine. It becomes greenish brown 

 from the surface downward on the addition of very little caustic soda 

 or ammonia with access of oxygen, and on shaking it quickly becomes 

 dark brown or black. It reduces alkaline copper solutions with even 

 slight heat, and ammoniacal silver solutions immediately in the cold. 

 It does not reduce alkaline bismuth solutions. It gives a lemon-colored 

 precipitate with MILLON'S reagent, which becomes light brick-red on 

 warming. Ferric chloride gives to the solution a blue color which soon 

 disappears. On boiling with concentrated ferric-chloride solution an 

 odor of quinone develops. With benzoyl chloride and caustic soda in 

 the presence of ammonia we obtain the amide of dibenzoylhomogentisic 

 acid, which melts at 204 C., and which can be used in the isolation of 

 the acid from the urine, and also for its detection (ORTON and GARROD). 

 Among the salts of this acid must be mentioned the lead salt containing 

 water of crystallization and 34.79 per cent Pb. This salt" melts at 

 214-215 C. 



In order to prepare the acid, heat the urine to boiling, add 5 grams 

 of lead acetate for every 100 cc., filter as soon as the lead acetate has 

 dissolved, and allow the filtrate to stand in a cool place for twenty -four 

 hours until it crystallizes (GARROD). The dried, powdered lead salt 

 is suspended in ether and decomposed by H 2 S. After the spontaneous 

 evaporation of the ether the acid is obtained in almost colorless crystals 

 (ORTON and GARROD 2 ). 



In regard to the quantitative estimation we proceed according to the sug- 

 gestion of BAUMANN by titrating the acid with a N/10 silver solution. For 

 details of this method the reader is referred to the works of BAUMANN, C. TH. 

 MORNER and MITTELBACH, GARROD and HURTLEY. DENIGES 3 has suggested 

 another method. 



Uroleucic acid, C 9 H 10 O 5 , is, according to HUPPERT, probably a dioxyphenyl- 

 lactic acid, C 6 H 3 (OH) 2 .CH 2 .CH(OH).COOH. This acid was first prepared by KIRK 

 from the urine of children with alcaptoriuria, which also contained homogentisic 

 acid. LANGSTEIN and MEYER 4 have also found a small amount of this acid in 



1 Baumann and Frankel, Zeitschr. f. physiol. Chem., 20; Neubauer and Flatow, 

 ibid., 52. 



2 Orton and Garrod, Joura. of Physiol., 27; Garrod, ibid., 23. 



3 Mittelbach, Deutsch. Arch. f. klin. Med., 71 (which contains the work of Bffumann 

 and Morner); Garrod and Hurtley, Journ. of Physiol., 33; Deniges Chem. Cenralbl. 

 1897, 1, 338. 



4 Huppert, Zeitschr. f. physiol. Chem., 23; Kirk, Brit. Med. Journ., 1886 and 188*8; 

 Langstein and Meyer, 1. c. 



