MUR

M U R

( H4 )

is a familiar example of a mucilaginous animalfluid. Animal mucus refembles gelatin fo clofelyboth in its ultimate analyfis and in many otherproperties, that the one is considered by Mr.Hatchett as only a modification of the other,and molt of what has been defcribed in thearticle Gelatin will therefore apply here.

Dr. Bollock a has however very clearly pointedout a very decided difference between the twoin the manner in which they are adted on bythe aqua lithargyri acetati, or Goulard’s ex-tract, a preparation of lead, made by faturatingboilihg vinegar with litharge. This liquorwhen added to any fluid containing animal mu-cus, gives a copious white precipitate, whereasit is not rendered fenlibly turbid by a folutionof pure jelly.

The infufion of galls or tan aifo which in-flantly precipitates jelly, has no etfe£I or fcarcelyany on mucus, and thefe two tefts thereforewill be fulhcient in moil inftances to detedf theprefence of one- or the other. Neithbir mucusnor gelatin are altered by the folution of corro-five fublimate, which however precipitates albu-men copioufly. Hence in a mixture of albu-men, gelatin and mucus, thefe fubftances maybe lepnrated with tolerable accuracy by the fuc-ccfiive application of corrofive fublimate, infu-fion of galls, and acetated litharge.

It is not eafy however to find the exactquantity of mucus by the folution of litharge,for the lead which it contains will be equallyprecipitated by fulphuric, muriatic, and phoi-phoric falts, all of which are found in manyanimal fluids. A further application of re-agents might indeed feparate the fulphat, mu-riat, and phofphat of lead, from that peculiarcombination formed by mucus and oxyd oflead, but the quantities of each are generallytoo fmall to allow of much accuracy in thismode of proceeding.

Animal mucus is generally combined withgelatin and albumen, and always with fomefalts, and on the whole it is one of the leaf!abundant of the animal fluids.

MURIATIC ACID. Acide Muriatique , Fr.Salzaure, Germ.

If a fmall retort or a proof bottle with acurved tube be half filled with well dried com--mon fait, and fome ftrong fulphuric acid bepoured upon it, a copious effervefcence takesplace, and the elaftic fluid thus extricated ap-pears in the form of a white vapour as foon asit comes in contact with the atmofphere : whenby the evolution of this gas all the common air* £dui. Med. St Surg. Journal.

has been driven out of the retort, the fubfe-quent portions of gas may be collected in theufual manner in glafs jars filled with mercuryand inverted in a bath of the fame fluid. Theair thus procured is known among chemifts bythe name of muriatic acid gas ; it is tranfparent,colourlefs, and pofTefTed of the fame mechanicalproperties as common air and other elafticfluids. Its fpeciiic gravity, according to Fon-tana, is about o\oo2C9, but according toKirwan, is = 0.00231, that of water being— 1000.0, and of atmofpheric air 0.C0123.It has a peculiarly fuffocating odour; to thetafte is extremely four and corrofive, and affedtsvegetable colours in the fame manner as otheracids. It is inftantaneoufly fatal to animal life,and is incapable of fupporting combuftion ; thispeculiarity however belongs to it, that if alighted taper is plunged into a jar full of it, theflame is confiderably enlarged and tinged of agreenifh yellow colour before it is extinguifhed.

Muriatic acid gas is not, properJy fpeaking,combuftible, though it unites without difficultywith a confiderable proportion of oxygen, form-ing Oxymuriatic Acid. The affinity betweenwater and muriatic acid is very powerful: evenwhen this fubftance is in a gafl'eous ftate it holdsa confiderable quantity of water, from which itcannot be freed otherwife than by the decom-pofition of this latter fubftance. If a little waterbe introduced into a jar of muriatic acid gasHanding over mercury, an immediate abforptiontakes place and the whole of the acid fuddenlylofes its gafl'eous ftate, heat being at the fametime given out. A firnilar though not io fuddenan cfteH is produced by charcoal, foft wood,fponge and various other porous bodies, pro-bably in confequence of their containing moif-ture. A piece of ice introduced into muriaticacid gas is melted as rapidly as if it was laid ona hot coal in confequence of the liberation ofcaloric during the combination of the water andacid. If alum or any other fait containing muchwater of cryftallizaticin be introduced into thisacid gas, an abforption takes place and the faitbecomes pulverulent in confequence of thetransfer of the greatefl part of its water to theacid. Iron filings, wax, phofphorus, fulphur.and other inflammable bodies when brought intocontact with muriatic acid gas abiorb more orlefs of it, and the refidue after wafhing withwater is inflammable; “ the caufe of which willbe explained prefently when we treat of thedecompofition of this acid. Neither azot norany of the Ample or compound inflammable* PiieiUcy on Air. Vol. ii. p. a 3 o.