ETHEREAL SULPHURIC ACIDS. 687 



The urine is first made faintly alkaline with soda, evaporated nearly to 

 dryness, and the residue thoroughly extracted with strong alcohol. 

 After the evaporation of the alcohol the residue is dissolved in water, 

 the solution acidified with sulphuric acid, and completely extracted by 

 agitating (at least five times) with fresh portions of acetic ether. The 

 acetic ether is then repeatedly washed with water, which is removed by 

 means of a separately funnel, then evaporated at a medium temperature 

 and the dry residue treated repeatedly with petroleum-ether, which 

 dissolves the benzoic acid, oxyacids, fats, and phenols, while the hippuric 

 acid remains undissolved. This residue is now dissolved in a little warm 

 water and evaporated at 50-60 C. to crystallization. The crystals are 

 collected on a small weighed filter. The mother-liquor is repeatedly 

 shaken with acetic ether. This last is removed and evaporated; the 

 residue is added to the above crystals on the filter, dried and weighed. 



Phenaceturic Acid, C 10 H n N0 3 = C 6 H 5 .CH2.CO.NH.CH 2 .COOII. This acid, 

 which is produced in the animal body by a combination of glycocoll with the phenyl- 

 acetic acid, CeH 5 .CH 2 .COOH, formed in the putrefaction of the proteins, has 

 been prepared from horse's urine by SALKOWSKi, 1 but it probably also occurs in 

 human urine. According to VASILIU 2 it is just as important a constituent of the 

 urine of herbivora as hippuric acid is. 



Benzoic Acid, C 7 H,,O 2 or C 6 H 5 .COOH, is found in rabbit's urine and sometimes, 

 though in small amounts, in dog's urine (\VEYL and v. ANREP). According to 

 JAARSVELD and STOKVIS and to KRONECKER it is also found in human urine in 

 diseases of the kidneys. The occurrence of benzoic acid in the urine seems to 

 be due to a fermentative decomposition of hippuric acid. Such a decomposition 

 may very easily occur in an alkaline urine or in one containing proteid (VAN DE 

 VELDE and STOKVIS). In certain animals pigs and dogs the kidneys, accord- 

 ing to SCHMIEDEBERG and MiNKOWSKi, 3 contain a special enzyme, SCHMIEDE- 

 BERG'S histozym, which splits the hippuric acid with the seoaration of benzoic 

 acid. 



Ethereal Sulphuric Acids. In the putrefaction of proteins in the 

 intestine, phenols, whose mother-substance is considered to be tyrosine, 

 indol and skatol are produced. These phenols directly, and the 

 two last-named bodies after they have been oxidized respectively into 

 indoxyl and skatoxyl, pass into the urine as ethereal sulphuric acids 

 after uniting with sulphuric acid. The most important of these ethereal 

 acids are phenol- and cresol-sulphuric acids which were formerly also 

 called phenol-forming substances indoxyl- and skatoxyl-sulphuric acids. 

 To this group also belong pyrocatechin-sulphuric acid, which occurs 

 only in very small amounts in human urine, and hydroquinone-sulphuric 

 acid, which appears in the urine after poisoning with phenol, and under 

 physiological conditions perhaps other ethereal acids occur which have 



thai as well as Pfeiffer, Bloch and Riecke, see Maly's Jahresber., 30 and 32. See also 

 Wiechowski, 1. c. 



1 Zeitschr. f. physiol. Chem., 9. 



2 Mitteil. d. landw. Inst., Breslau, 4. 



3 Weyl and v. Anrep. Zeitschr. f. physiol. Chem., 4; Jaarsveld and Stokvis, Arch. 

 f. exp. Path. u. Pharm., 10; Kronecker, ibid., 16; Van de Velde and Stokvis, ibid., 

 17; Schmiedeberg, ibid., 14, 379; Minkowski, ibid., 17. 



