U R I
U R I
( 45 .
'The yellow ox yd when mixed with the com-mon enamelling flux, tinges porcelain of a deeporange yellow.
The alloys of uranium are as yet wholly un-ion wit.
UREA. See Urine.
UlTC, or LITHIC ACID. See Uri-Ni ; v Cai.cui.cs.
URINARY CALCULUS.
In the bladder of many animals, and particu-larly of man, hard round concretions, ftony inappearance, .are frequently formed, which pro-duce mo ft dreadful paroxvfms of pain andgeneral difeafe, for which no radical cure hashitherto been difcovered, except a very feriousiitrgical operation.
The Hone of the bladder has been examined■with extreme attention by fevcral molt excellentchemifts, who have been frimuiated by the ad-ditional hope of finding a foivent which mightremove it altogether, or at leaft mitigate thefeverity of the fymptoms which it produces,and it was early difcovered that a confiderablebenefit -was derived from the internal ufe of al-kaline medicines, taken in as large quantity ascould be borne, and for a length of time.
The firft and by far the molt important dif-covery relating to the chemical nature of calcu-lus, was made by Scheele , in 1776/ who ob-tained from it a large proportion of a peculiarcryftallizable fubftance till then unknown, whichhad all the properties of a very -weak acid, par-ticularly in reddening litmus, and neutralizingalkaline and .earthy bafes. This fubftance wasafterwards denominated the Lithic Acid , andmore lately the Uric Acid . This difeovery gavea new intereft to the examination of calculi,and many additional obfervations have beenadded by other chemifts. Bergman, who wasemployed on the fame fubjed at the fame timewith Scheele , gave feme further remarks on itshabitude with acids. Dr. Wollafton b has{hewn that the gouty calculus, or chalk Jlone ,as it is generally called, confifts of the lithicacid neutralized by foda, and has alfo addedlargely to our knowledge of the varieties ofurinary calculi, by difeovering that phofphat ofammonia and magnefia is the compofition ofone fpecies ; that pure phofphat of lime formsanother .fpecies; and that the variety known tofurgeons by the name of the mulberry calculus,confifts of phofphat and oxalat of lime. c Dr.Pearfon in analyfing 200 fpecimens of calculi,has found the lithic acid of Scheele in all butfix, in very various proportions, but he confiders
*.£ flays. * Phil. Ttwi'. for 1797. e Ibid, for 1798.
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this peculiar fubftance rather as an animal'oxydthan an acid. Brugnatelli and other chemiftswhom it is needlefs to enumerate, have thrownfome further light on this fubjed; and laftly,a long and moft elaborate feries of experimentshas been made by Meflrs. Fourcroy and Vau-quelin, which gives the fulleft and moft com-preheniive view of the fubjed. d
From all thefe authorities we may colledthe following particulars :
The greater number of urinary calculi orftones of the bladder, are of a round or ovalfhape, varying in fize from that of a bean tothe bignefs of a pullet’s egg; brittle, hardenough to take a good poliih ; when fawnthrough obvioufly compofed of concentric lami-nae formed round a fmall nucleus; of a dullyellow to a red gravelly colour, often inter-iperfed with blood-red fpots; and the fpecificgravity of even the heavieft, does not quiteamount to 2. Thefe are the calculi in whichthe lithic or uric acid enters as a conftituentpart, but even in thefe there is a confiderablevariety of texture, and appearance, the furfacebeing fometimes fmooth and polifhed, fome-times rough, with fmall protuberances, and oc-cafionally interfperfed with cryftals, which latterare the ammoniaco-magnefian phofphat.
The mulberry calculi, as they are called, arediftinguilhed by their mamillated, and ufuallypolifned furface, refembling that of the mul-berry, and their colour too is generally muchdarker. Thefe, as before mentioned, have beenfound by Dr. Wollafton to confift chiefly ofoxalat of lime. The analyfis of this and of theother rarer varieties, will be mentioned after wehave described the common lithic calculus,which is particularly diftinguilhed by its lamellartexture, its toughnefs, and the uniform brownyellow colour of the inner part, a good dealrefembling petrified wood in appearance.
When this calculus is boiled for fome timein water, a folution is obtained holding about8 grains in 5 oz. of liquid, which reddens lit-mus paper.' As it grows cold the greateft:part of the diflolved portion of calculus feparatesagain in the form of fine cryftals, which are thepure Lithic or Uric acid. The muriatic acidhas no effed on this calculus. Concentratedfulphuric acid diflolves it by the affiftancc ofheat. But the moft charaderiftic efl'eds are thofeproduced by the nitric acid. When this acid,iomewhat dilute, is boiled on the calculus, thelatter is entirely diflolved, red vapours arife, anda good deal of carbonic acid gas is produced.