254 THE U1UXK. 



on treating with concentrated hydrochloric acid, and on subsequent 

 oxidation the liberated skatoxyl yields pigments which are for the 

 most part of a red color. Of their chemical nature, however, 

 nothing is known. One of these may possibly be identical with 

 Rosin's urorosciii. Rosin, to be sure, claims that the chromogen of 

 urorosein is not a conjugate sulphate but we know that a portion of 

 the skatol also appears in combination with glucuronic acid in the 

 urine, and it is hence possible that his pigment may be derived from 

 this source. Urines containing notable quantities of skatoxyl 

 become darker on exposure to the air, and may gradually turn a 

 reddish-violet or almost a black color. This change, as in the 

 phenol urines, begins at the surface and gradually extends down- 

 ward. 



Tests. To demonstrate the presence of skatoxyl in urine, this 

 is strongly acidified with hydrochloric acid and extracted with 

 amyl alcohol, which takes up the coloring-matter. Chloroform 

 and ether do not dissolve this in acid solution, but do so in neutral 

 or alkaline solution, providing that the pigment has been freshly 

 formed. 



Test for Urorosein (so-called). A few cubic centimeters of urine 

 are treated with an equal amount of concentrated hydrochloric acid 

 and one or two drops of a strong solution of calcium hypochlorite. 

 The indigo-blue is extracted with chloroform, and it will now be 

 observed that the supernatant fluid presents a red color. On shaking 

 with amyl alcohol this takes up the red pigment, which is thus 

 manifestly not identical with indigo-red. Upon the addition of 

 sodium hydrate to the alcoholic solution the color disappears, but 

 reappears upon the subsequent addition of hydrochloric acid. On 

 standing, the color gradually disappears. Under normal conditions 

 this reaction is not well marked, but becomes quite distinct in cases 

 in which intestinal putrefaction is much increased. 



A portion of the skatol, as I have already stated, appears in the 

 urine as skatol-carbonic acid : 



3C.COOH. 



The substance is usually present in exceedingly small amounts, 

 however, and has not been isolated in substance. To demonstrate 

 its presence even, it is necessary to work with several liters of 

 urine. To this end, the fluid (5000-6000 c.c.) is evaporated to a 

 syrup ; the residue is extracted with absolute alcohol, the alcoholic 

 solution is evaporated, and the remaining material extracted with 

 ether after acidifying strongly with sulphuric acid. From the 

 ethereal solution the substance is obtained in aqueous solution by 

 shaking with a dilute solution of sodium hydrate. The alkaline 

 solution is then evaporated and the residue extracted with alcohol. 

 This extract is now concentrated to about 100 c.c. and precipitated 



