1 270 



URINE 



is now precipitated witli acetate of baryta> in 

 order to rid it of sulphuric acid. The sulphate 

 of baryta is collected on a filter, and the 

 filtered liquor neutralised with ammonia, and 

 then again thrown down with the acetate, 

 which now causes a precipitate of phosphate 

 of baryta.* This is to be collected, and the 

 filtered liquor evaporated in order to drive 

 oft' the ammonia ; or, what is better, it may be 

 neutralised by acetic acid. Neutral acetate of 

 lead is now added to the solution, which 

 causes a copious precipitate. This must 

 be collected and washed, and then decom- 

 posed by sulphuretted hydrogen, which pre- 

 cipitates sulphuret of lead, and leaves the 

 animal extractive in solution. This may be 

 obtained by evaporation. This extractive is, 

 however, but part of that meant to be under- 

 stood as the " animal extractive soluble in 

 water only," so often mentioned in analyses. 

 The remainder of it may be procured by pre- 

 cipitating the liquor (in which the precipitate 

 by neutral acetate of lead subsides), by means 

 of the di-acetate of lead ; then collecting the 

 precipitate, decomposing it as before by sul- 

 phuretted hydrogen, and procuring the ex- 

 tractive from the clear liquor. It must be re- 

 membered that each of these extractives has 

 peculiar properties, perhaps dependent on the 

 processes used to obtain them. There is 

 also a portion of animal extractive left unpre- 

 cipitated by the di-acetate of lead. It is 

 easily obtained from the liquor by ridding the 

 solution of any lead which may exist in it by 

 means of sulphuretted hydrogen, filtering, and 

 then evaporating to dryness. 



It is a mixture of these three peculiar ex- 

 tractives which constitutes the "animal ex- 

 tractive soluble in water only" of Berzelius. 



The properties of the extractive matter pre- 

 cipitated by the neutral acetate of lead are 

 as follows : 



It is of a brownish colour, translucid, and 

 doi>s not deliquesce ; has no taste, and scarcely 

 affects litmus paper. 



Its solution is rendered cloudy by corrosive 

 sublimate, and more so by the protochloride 

 of tin. 



The extractive precipitable by the di-ace- 

 tate of lead has the following properties: 



It is of a yellowish brown colour ; it has a 

 slightly bitter taste, and does not deliquesce. 



The watery solution of this extract is of a 

 deep yellow colour. 



It is not precipitable by the solution of bi- 

 chloride of mercury ; but the protochloride of 

 tin, the di-acetate of lead, and nitrate of silver 

 precipitate it of a dark brown colour. 



The third extractive, which was precipitated 

 neither by the acetate nor di-acetate of lead, 

 possesses the following characters: 



It is of a yellow colour. Solutions of bi- 

 chloride of mercury, protochloride of tin, and 

 nitrate of silver precipitate its aqueous solu- 

 tion. The precipitate produced by the last of 



* Both these precipitates produced by acetate of 

 baryta contain animal matter, which, in the latter 

 case, is in very considerable proportion. 



these re-agents is of a dirty yellowish red 

 colour.* 



Colouring matters. These are two in num- 

 ber, Haemaphaein or the brown; and Uroery- 

 thrin, or the red. 



a. HcBmaphcein. This is the substance which 

 gives the yellow or brownish yellow tint to 

 urine, and according to its proportion the 

 urine assumes a lighter or deeper colour. Ac- 

 cording to Scharling, the odour also of the 

 urine depends on this principle. It is soluble 

 in alcohol, and the alcoholic solution reddens 

 litmus. The odour, when concentrated, is 

 said to resemble that of castor. Scharling be- 

 lieves this colouring matter to be an oxide 

 of a radical, to which he has given the name 

 of omichmyle. 



/3. Uroerythrin. This exists but in very 

 minute quantity in healthy urine ; it attaches 

 itself especially to the lithic acid, being pre- 

 cipitated with that principle on all occasions. 

 It becomes abundant in some forms of disease. 



Mucus. For the history of this substance 

 see article Mucus. 



Uric or lithic acid. This acid may be pro- 

 cured from the urine by the addition of a few 

 drops of strong hydrochloric acid, which, after 

 the lapse of some hours, produces a reddish 

 crystalline precipitate of lithic acid. This red 

 colour is caused by an admixture of colouring 

 matter of urine, for pure lithic acid is per- 

 fectly white. It may be obtained in a pure 

 state from the red crystals by being dissolved 

 in caustic potash, and then precipitated from 

 its solution by the addition of hydrochloric 

 acid. The precipitate may now be collected, 

 and washed on a filter. 



Lithic acid possesses the following chemical 

 properties : 



It is insoluble in water. 



It is easily soluble in a solution of caustic 

 alkali, and precipitated from such solution by 

 the addition of an acid. 



It is dissolved by nitric acid with efferves- 

 cence ; and, by careful evaporation to dry- 

 ness, yields a red or rather pink colour, which 

 becomes of a fine violet tint when ammonia 

 is dropped on it, or even when it is subjected 

 to the action of strong ammoniacal fumes. 

 This reaction of ammonia is very useful, in- 

 asmuch as it prevents the yellow stain which 

 many animal matters produce with nitric acid 

 from being mistaken for this reaction of lithic 

 acid. In the former case, the ammonia in- 

 creases the yellow tinge to an orange colour, 

 which is very distinct from the beautiful violet 

 tint of what is now known as murexid. 



Before the blowpipe, this substance emits a 

 fetid smell of burnt horn, mixed with an odour 

 approaching to that of hydrocyanic acid. 



The ultimate analysis of lithic acid shows 

 its composition to be C 5, N 2, H 2, O 3. 



Hippuric acid. This acid is considered by 

 Liebig to be constantly present in human 

 urine. 



* For farther examination of these extractive 

 matters, see the article by Berzelius, in his Tniite 

 de Chimie, vol. vii. p. 380. ; Sur les Matieres iiide'- 

 terminc'es dans 1'Urine. 



