COLOUPJNG-MATTERS OF URINE. 403 



and injection of benzoic acid into the blood, hippuric acid was found in the muscles, blood, and 

 liver, goes to show that it must be formed in other organs beside the kidneys. The power of 

 changing benzoic acid introduced into the human body, into hippuric acid, may even be 

 abolished in disease of the kidney. Under certain circumstances it seems that hippuric acid, 

 already formed, may be again decomposed in the tissues. 



It is greatly increased after eating pears, plums, and cranberries ; in icterus, some liver 

 affections, and in diabetes. When boiled with strong acid or alkalies, or with putrid substances, 

 it takes up H 2 and splits into benzoic acid and glycin. 



Preparation. Add milk of lime to the fresh urine of horses or cows to form calcic hippurate. 

 Filter, evaporate the filtrate to a small bulk, and precipitate the hippuric acid with excess of 

 hydrochloric acid. To purify the hippuric acid, crystallise it several times from a hot watery 

 solution. 



Cynuric Acid. C. 20 H 14 N. 2 O 6 + H 2 occurs in the urine of dogs (J. v. Liebig). 



Allantoin, C 4 H 6 N 4 3 , which occurs in the amniotic fluid of the cow, is found in 

 minute traces in normal urine after flesh food, and is more abundant during the 

 first weeks of life, and during pregnancy. 



After large doses of tannic acid, the amount is increased (Schottin), while in dogs feeding with 

 uric acid also increases it (Salkowski). 



Properties. It forms shining, prismatic crystals ; from the urine of sucking calves it 

 crystallises in transparent prisms. It is decomposed by ferments into urea, ammonium oxalate, 

 and carbonate, and another as yet unknown body. Preparation (a) the urine is precipitated 

 with basic lead acetate, the lead in the filtrate is removed by sulphuretted hydrogen, and the 

 filtrate itself is then evaporated to a syrup, from which the crystals separate, after standing 

 for several days. They are then washed with water, and recrystallised from the water 

 (Salkoivski). 



261. COLOURING-MATTERS OF THE URINE. 1. Urobilin is most 

 abundant in the highly coloured urine of fevers, but it also occurs in normal urine 

 (Jaffe). It is identical with the hydrobilirubin of Maly ( 117, 3, g). It is a de- 

 rivative of hsematin, which also yields the bile-pigments ( 177). It gives a red, or 

 reddish-yellow colour to urine, which becomes yellow on the addition of ammonia. 



[MacMunn, chiefly from spectroscopic observations, finds that two entirely different substances 

 have been included under the name of " urobilin," viz., that of normal and that of pathological 

 urine, and that hydrobilirubin is not identical with either. The pathological urobilin seems 

 to be closely connected with stercobilin ( 185).] 



Preparation. Prepare a chloroform extract of urine containing urobilin add iodine to the 

 extract, and remove the iodine by shaking the mixture with dilute caustic potash, which forms 

 potassic iodide. This potash solution becomes yellow or brownish-yellow, and exhibits beauti- 

 ful green fluorescence {Gerhardt). 



Urobilin may be extracted from many urines by ether {Salkoivski). When subjected to the 

 action of reducing agents, e.g., sodium amalgam, a colourless product is obtained, which on 

 exposure to the air absorbs 0, and becomes re transformed into urobilin. This colourless body 

 is identical with the chromogen which Jaffe found in urine. 



If urine is treated with soda or potash, the characteristic absorption-band lying between b and 

 F, passes nearer to b, becomes darker and more sharply defined. According to Hoppe-Seyler, 

 urobilin is formed in urine after it is voided, from another urobilin-forming body (Jaffe's 

 chromogen) absorbing oxygen. If urine containing urobilin be made alkaline with ammonia, 

 and zinc chloride be added, it exhibits marked fluorescence ; it has a green shimmer by reflected 

 light. When urobilin is isolated, it fluoresces without the addition of zinc chloride. In cases 

 of jaundice ( 180), where Gmelin's test sometimes fails to reveal the presence of bile-pigments, 

 urobilin occurs. This " urobilin-icterus " {Gerhardt) occurs chiefly after the absorption of large 

 extravasations of blood. . According to Cazeneuve, the urobilin is increased in all diseases 

 where there is increased disintegration of coloured blood-corpuscles. 



2. Urochrome ( Thudichum) is regarded as the chief colouring-matter of urine. It may be 

 isolated in the form of yellow scales, soluble in water, and in dilute acids and alkalies. The 

 watery solution oxidises, and when exposed to air becomes red owing to the formation of 

 uroerythrin. When acted on by acids, new decomposition -products are formed, e.g., urome- 

 lanin. Uroerythrin gives the red colour to deposits of urates ( 258). 



3. A brown pigment containing iron is carried down with uric acid, which is precipitated 

 on the addition of hydrochloric acid ( 258). By repeatedly adding sodic urate to the urine, 

 and precipitating the uric acid by hydrochloric acid, a considerable amount may be obtained 

 {Kunkel). 



4. Urine boiled with HC1 yields a garnet-red crystalline pigment, urorubin, to ether. 



In cases of melanotic tumours, there has been occasionally observed urine, which becomes 

 dark, owing to melanin ( 250, 4), or to a colouring-matter containing iron {Kunkel). . 



