U R I

U R I

( 4 1

Fourcroy and Vauquelin ." Its compofition hasbeen partially explained under the article Phof-phortts and Phofphats, as it was the fubftancefrom which phofphorus was firft extradited.

The fubftances which unqueftionably com-pofe healthy urine before any change has beeninduced by putrefaction or artificial heat, arethe following, viz. water, phofphoric acid,muriatic acid, uric acid, benzoic acid, carbonicacid, foda, potafh, ammonia, lime, magnefia,gelatin, and a very lingular fubftance peculiarto this fluid, to which was formerly giventhe vague term of a faponaceous extract, butwhich has more properly been called urea (uree )by the French chemifts above mentioned. Be-fides thefe component parts, Prouft and fomeother chemifts have admitted a peculiar refin, towhich the colour and odour is attributed;fulphur, and fulphuric acid, united partly withthe foda and partly with the lime. But thefethree laft fubftances are doubtful, and theymay be pafled over.

Of the above mentioned indubitable ingredi-ents of urine all the acids are nearly, but notentirely, faturated with one or other of therefpeftive bafes (for a flight excefs of acid isfliewn in recent urine by its reddening litmus)fo that a number of neutral falts are formed,and may be adlually extrafted by fimple pro-cefles. Of thefe the moil important are, muriatof foda and potalh ; phofphat of lime ; phof-phat of foda ; and phofphat of foda with ammo-nia, a fait long celebrated under the term Micro-tofmic fait, or Fuftble fait of Urine. Befides thefe,after putrefaction has begun in this fluid, aconfiderable quantity of ammonia is generated,which not only faturates the excefs of acid, butgives a very fenfibie aicalefcencv, and caufes theproduction of fome other neutral falts, particu-larly the uratof ammonia ; benzoat of ammonia;and, by uniting with the phofphat of magnefiait forms the triple ammoniaco-magnefian phof-'phat deferibed in the article of urinary calculus.

Urine, recently made by a perfon in health,is a clear yellow fluid, varying in fpecific gravityfrom 1.033 to I -°° 5 > ° according as it is moreor lefs watery, of a peculiar fmell, a very acridfaline tafte, and {lightly acidulous fo as to reddenlitmus. After Handing for fome hours it be-comes turbid, and a red matter is depofited,■which is chiefly uric acid, and may be re-dif-folved by heating the urine.

When urine is expoied to a gentle heat inan evaporating veffd a fieam a:ife. c , impreg-nated with an urinous odour, and a ieum arifes

‘ Aun.Chim tom. 31 & 3 *.

)0 )

with many globules of gas entangled in it,which are chiefly carbonic acid. d As the eva-poration advances the colour deepens to a darkred, and foon a whitifh flocculent coagulum isdepofited, and the fteam acquires an ammoni-acal fmell. At this period the excefs of acidexifting in recent urine is loft, and on the con-trary it turns fyrup of violets green, which,together with the acquired ammoniacal fmell,indicates the formation of a quantity of thisalkali by the a£tion of the heat. This circum-ftance too has another effect, which is to pre-cipitate the phofphat of lime which was held infolution by the excefs of acid, and the whitifhcoagulum confifts of this earthy fait, togetherwith an animal matter of the nature either ofgelatin or albumen, and of fome urat of ammo-nia. When the evaporation is continued tiilthe liquor has a fyrupy confiftence, this, whendecanted from the fedin ent, and fet in a coolplace depofits a confiderabl: quantity of browndirty cryftals. To feparate the whole of thefe,the fupernatant liquor fhould be alternately eva-porated and fet by to cool, till the whole isbrought nearly to drynefs. By re-difi'olving allthe foul cryftals in warm water and againcryftaliizing, the falts may be obtained pure ;but for the purpofe of analyfis it is better firftto digeft the entire mafs, both cryftals andrefidue, with good alcohol, which will not fen-fibly a£t on the falts, but will diflolve the ex-tradbive matter with which they are mixed, andthat of the refidue, which confifts chiefly ofthe urea.

The falts confift of the muriats of potafli andfoda, phofphat of foda, and of the phofphat offoda with ammonia, or fufible fait. If after beingrediflolved, the folution is ftrongly evaporatedand fet by to cool, a confufed aflemblage ofcryftals is formed, which was formerly confi-dered without much difiinction, as the nativefait of urine. But if the folution is allowed toevaporate fpoptaneoufly, the muriats firft fepa-rate, after which fmall cryftals of phofphat ofammonia are formed, and along with themlarger cryftals of Ample phofphat of foda, whichlatter may be diftinguiflied by their fize, bytheir form of compreffed four-fided prifms, byeflforefcing, and by running into an opakeglafs when melted ; whereas the pure phofphatof ammonia when heated parts with its alkali,and a clear globule of phofphoric acid is left.(For the further habitudes of thefe two falts feethe article Phofphats.)

The above fimple method of analyfis there?

• Crsikilunk. * 4