150 



CHEMISTRY. 



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rirsh unne differs considerably in its appearance, ac- 

 cording to the e person, and the time at which 



it it voided. la general, healthy urine is a transparent 

 liquid of a li^ht amber colour, an aromatic odour resem- 

 bling that of violets, and a disagreeable bitter taste. Its 

 specific fjrnvity varies, according to Mr Cniick-hanks, 

 from 1.005 to 1.033. When it cools, the aromatic sn-..-ll 

 leaves it, and i> succeeded by another, well known by 

 the name of urinous tmcll. 



1. Urine reddens paper stained with turnsole and with 

 the juice of radishes, and therefore contains an acid. 

 This acid has been generally considered as the phospho- 

 ric ; but Thcnard has shown that it is in reality the 

 acetic. 



2. If a solution of ammonia be poured into fresh urine, 

 a white powder precipitates, which has the properties of 

 phosphate of lime. 



3. If the phosphate of lime precipitated from urine 

 be examined, a little magnesia will be found mixed with 

 it. Fourcroy and Vauquelin have ascertained, that this 

 is owing to a little phosphate of magnesia which urine 

 contains, and which is decomposed by the alkali of lime 

 employed to precipitate the phosphate of lime. 



4. Proust informs us, that carbonic acid exists in urine, 

 and that its separation occasions the froth which appears 

 during the evaporation of urine. 



5. Proust has observed, that urine kept in new casks 

 deposites small crystals, which effloresce in the air and 

 fall to powder. These crystals possess the properties of 

 the carbonate of lime. 



6. When fresh urine cools, it often lets fall a brick- 

 coloured precipitate, which Scheele first ascertained to 

 be crystals of uric acid. All urine contains this acid, 

 even when no sensible precipitate appears when it cools. 



7. During intermitting fevers, and especially during 

 diseases of the liver, a copious sediment of a brick-red 

 colour is deposited from urine. This sediment contains 

 the rosacic acid of Proust. 



8. If fresh urine be evaporated to the consistence of 

 a syrup, and muriatic acid be then poured into it, a pre- 

 cipitate appears, which possesses the properties of ben- 

 zoic acid. 



9. When an infusion of tannin is dropt into urine, a white 

 precipitate appears, having the properties of the combi- 

 nation of tannin and albumen or gelatine. Their quan- 

 tity in healthy urine is very small, often indeed not sen- 

 sible. Cruickihariks found that the precipitate afford- 

 ed by tannin in healthy urine amounted to -j^th part of 

 the weight of the urine. 



10. If urine be evaporated by a slow fire to the con- 

 tistence of a thick syrup, it assumes a deep brown co- 

 lour, and exhales a fetid ammouiacal odour. When al- 

 lowed to cool, it concretes into a mass of crystals, com- 

 posed of all the component parts of urine. If four times 

 its weight of alcohol be poured into this mass, at inter- 

 valt, and a slight heat he applied, the greatest part of it 

 is dissolved. The alcohol which has acquired a brown 

 colour, is to be decanted off, and distilled in a retort in 

 sand heat, till the mixture has boiled for some time, 

 and acquired the consistence of a syrup. By this time 

 the whole of the alcohol has passed off, and the m, it'-r, 

 n cooling, crystallizes in quadrangular plates which in- 

 tersect each other. This substance is urea, which com- 

 pote* /o-t'fM of the urine, provided the watery part be ex 

 eluded. To this substance the taste and smell of urine 

 arc owing. It is a substance which characterises urine, 



and constitutes it what it is, and to which the greater 

 part of the very singular phenomena of urine are to be 

 ascribed. 



11. According to Fourcroy and Vauquelin, the co- 

 lour of urine depends upon the urea: the grea:er the pro- 

 portion of urea, the deeper the colour. But Proust has 

 detected a resinous matter in urine similar to the resin 

 of bile j and to this substance he ascribes the colour of 

 urine. 



1 '_'. If urine be slowly evaporated to the consistence of 

 a syrup, a number of crystals make their appearance on 

 its surface j these possess the properties of the muriate. 

 of soda. 



13. The saline residuum which remains after the sepa- 

 ration of urea from crystallized urine by means of alcohol, 

 has been long known by the names of fusible salt o/ 

 urine and microeosmrc sail. 



When these salts are examined, they are found to have 

 the properties of phosphates. The rhomboidal prism" 

 conMst of phosphate of ammonia united to a little pho.-- 

 phate of soda ; the rectangular tables, on the contrary, 

 are phosphate of soda, united to a small quantity ui 

 phosphate of ammonia. Urine, then, contains phosphate 

 of soda and phosphate of ammonia. 



14. When urine is cautiously evaporated, a few cubic 

 crystals are often deposited among the other salts ; these 

 crystals have the properties of muriate of ammonia. 



15. When urine is boiled in a silver bason, it blackens 

 the bason ; and if the quantity of urine be large, small 

 crusts of sulphuret of silver may be detached. Hence 

 we see that urine contains sulphur. 



Urine, then, contains the following substances : 



l-'i.imina- 

 (itm of 

 Nature. 



10. Albumen. 



11. Urea. 



12. Resin. 



13. Muriate of soda. 



14. Phosphate of soda. 



15. Phosphate of ammonia. 



16. Muriate of ammonia. 



17. Sulphur. 



foinpori- 

 tjon. 



1. Water. 



2. Acetic acid. 



S. Phosphate of lime. 



4. Phosphate of magnesia. 



5. Carbonic acid. 



6. Carbonate of lime. 



7. Uric acid. 



8. Rosacic acid. 



9. Ben/oic acid. 



These are the only substances which are constantly 

 found in healthy urine ; but it contains also occasionally 

 other substances. Very often muriate of potash may be 

 distinguished among the crystals which form during its 

 evaporation. The presence of this salt may always be 

 detected by dropping cautiously some tartaric acid into 

 urine. If it contains muriate of potash, there will preci- 

 pitate a little tartar, which may be easily recognized by 

 its properties. 



Urine sometimes also contains sulphate of soda, and 

 even sulphate of lime. The presence of these salts may 

 be ascertained by pouring into urine a solution of muriate 

 of barytes ; a copious wliitt? precipitate appears, consist- 

 ing of the barytes combined with phosphoric acid, and 

 with sulphuric acid, if any be present. This precipitate 

 must be treated with a sufficient quantity of muriatic 

 acid. The phosphate of barytes is dissolved, but the 

 sulphate of barytes remains unaltered. 



SECT. XXII. Of Morbid Concretions. 



Hard substances occasionally make their appearance in Morbid 

 different parts of the animal body, both in the solids and concrc- 

 the cavities destined to contain the fluids. In the first tioiw. 

 case they are denominated concretions or otsi/icati ns ; 

 in the second calculi. Their formation is an irregularity 

 in the animal oeeouomy, and they often produce the most 

 excruciating diseasts. They may be divided into five 



