404 INDICAN AXD ITS TESTS. 



262. INDIGO, PHENOL, KRESOI, PYROKATECHIN, AND SKATOL- 



FORMING SUBSTANCES. 1. Indican [C s H 7 NS0 4 ], or indigo-forming sub- 

 stance (Schunck), is derived from indol, C S H 7 N, the basis of indigo, which is 

 formed in the intestine by the pancreatic digestion of proteids ( 170, II.), but it 

 also arises as a putrefactive product ( 184, 6). Indol, when united with the 

 radical of sulphuric acid, HS0 3 , and combined with potassium, forms the so-called 

 indigogen or indican of urine (Brieger, Baumann). This substance (CsH^NSC^K 

 = potassium indoxyl-sulphate) forms white glancing tablets and plates ; readily 

 soluble in water and less so in alcohol. By oxidation it forms indigo-blue; 

 2 indican + Oo = C 1(5 H 10 N 2 O 2 (indigo-blue) + 2HKS0 4 (acid potassic sulphate). It 

 is more abundant in the urine in the tropics, and it is absent from the urine of 

 the newly-born {Senator). 



Tests. (1) Add to 40 drops of urine, 3 to 4 c.c. of strong fuming hydrochloric acid, and 2 

 to 3 drops of nitric acid. Boil, a violet-red colour (with the deposition of true crystalline 

 indigo-blue (rhombic) and indigo-red attests its presence. Putrefaction causes a similar decompo- 

 sition in indican ; hence, we not unfrequently observe a bluish-red pellicle of microscopic crystals 

 of indigo-blue, or even a precipitate of the same. (2) Mix in a beaker equal quantities of urine 

 and hydrochloric acid, and add two drops of solution of chlorinated lime ; the mixture at first 

 becomes clear, then blue (Jaffe). Add chloroform, and shake the mixture vigorously for some 

 time ; the chloroform dissolves the blue colouring matter, which is obtained as a deposit, 

 when the chloroform evaporates (Senator, Salkowski). (3) Heat to 70 one part of urine with 

 two parts of nitric acid, and shake up with chloroform ; the chloroform dissolves the indigo 

 which is formed, assumes a violet colour, and gives an absorption band between C and D, 

 slightly nearer D (Hoppe-Seyler). Quantity. Jafle found in 1500 c.c. of normal human urine, 

 4*5 to 19 - 5 milligrammes of indigo ; horse's urine contains 23 times as much. The subcutaneous 

 injection of indol increases the indican in the urine (Jaffe). E. Ludwig obtained indican by 

 heating hee matin or urobilin with a caustic alkali and zinc dust. It has also been found in the 

 sweat (Bizio). 



Pathological. The indican in the urine is increased when much indol is formed in the 

 intestine ( 172, II.), e.g., in typhus, lead colic, trichinosis, catarrh, and haemorrhage of the 

 stomach, cholera, carcinoma of the liver and stomach ; obstruction of the bowel or ileus, 

 peritonitis, and diseases of the small intestine. 



2. Phenol, C (5 H O (carbolic acid, 252), was discovered by Stadeler in human 

 urine (more abundant in horse's urine). It does not occur as carbolic acid, but in 

 combination with a substance from which it is separated by distillation with dilute 

 mineral acids. The "phenol-forming substance" is, according to Baumann, 

 " phenolsulphonic acid " (C 6 H 5 0, S0 3 H), which in urine is united with potash. 



rhenol is derived from the decomposition of proteids by pancreatic digestion ( 172, II.), 

 and also from putrefaction ( 184, 6), the mother-substance being tyrosin. Hence, the forma- 

 tion of phenolsulphonic acid is analogous to the formation of indican. 



If in the employment of carbolic acid it be absorbed, the phenolsulphonic acid becomes greatly 

 increased in amount, so that sulphuric acid must be united with it ; hence, alkaline sulphates 

 are decomposed in the body, so that the latter may be absent from the urine (Baumann). 

 Living muscle or liver, when digested in a stream of air for several hours with blood to which 

 phenol and sodic sulphate are added, yields phenolsulphonic acid ; while, under the same cir- 

 cumstances, pyrokatechin forms ethersulphonic acid. 



Carboluria. When carbolic acid is used externally or internally, and it is absorbed, it causes 

 a deep dark-coloured urine due to the oxidation of phenol into hydrochinon (orthobioxy benzol 

 ^ C fl H 6 Oo), which for the most part appears in the urine as ethersulphonic acid (Baumann and 

 others). 



3. Parakresol (hydroxyltoluol, C 7 H s O), with its isomers ortho- and meta-kresol 

 (the latter in traces), is more abundant in urine (Baumann, Preusse). It also 

 occurs in combination with sulphonic acid. 



Test for phenol (and also kresol) : Distil 150 c.c. urine with dilute sulphuric acid. The 

 distillate gives a brown crystalline deposit of tribromophenol with bromine water, as well as a 

 red colour with Millon's reagent. 



Hydroxybenzol (pyrokatechin, hydrochinon) is obtained from urine, when it is heated for a 

 long time with hydrochloric acid. 



Resorcin, which is an isomer of hydrochinon, when administered internallv, also appears in 

 the urine as ethersulphonic acid. Toluol and naphthalin behave similarly. Benzol is oxidised 

 to phenol. 



