GLI
G L U
( 514 )
The native Glauber’s fait however, efpeciallywhen efflorefcent, contains befides pure fulphatof foda, fome oxyd of iron, accidental earthyimpurities, and more or lefs of muriat andcarbonat of foda. It is met with in old falt-mines, on the borders of falt-lakes in Hungary ,Tartary, and Egypt , and on the furface of cer-tain peat moffes elpecially in the north of France .
It is contained in folution in the Natron-lakesof Egypt , and the mineral fprings of Carlfbad. bGLIMMER. See Mica .
GLIMMERSCHIEFER. See Micaceous
SCHISTUS.
GLUTEN, (Animal.) See Fibrin , andBlood .
GLUTEN , •vegetable. A fubftance very clofe-ly refembling animal gluten in all the effentialchemical properties, is found in feveral vege-tables, and hence it has received the name ofvegetable gluten.
Wheat flour was firft found by Beccari tocontain it in confiderable quantity, and it isfrom this fource that it is ufually obtained forexperiment by tire following Ample and eafyprocefs.
Moiften any quantity of wheat flour with alittle water, and knead it with the hand into atough ductile pafte, then let a very flenderftream of water keep dropping on the paftewhile it is inceffantly worked about with thehands, and the water will run off white andturbid, owing to the fecula or ftarch which itcarries off. The pafte in the mean time gra-dually becomes more of a grey and almoft femi-tranfparent appearance, and when the waterruns off quite clear, nothing is left in the handsbut pure gluten. No other precaution is re-quired in this preparation but that of not drench-ing the flour at ftrft with water, but only uflnga very fmall quantity with much kneading, thatthe gluten may not be carried off along withthe ftarch. Good wheat flour will yield in thisway about a fourth of its weight of gluten, andno other flour but that of wheat will yield itexcept in a very fmall proportion, and henceprobably the peculiar property of wheat flour tomake bread without any other addition than aferment. See the article Bread .
Gluten thus prepared is foft, extremely tena-cious and eiaftic, fo as to bear being extendedconflderably without pulling in pieces, and re-turning to its former dimenfions. It is alfoconflderably adhefive, readily flicking to thefingers. Its colour is a dirty grey, and it has ak IClapr. analy. Els. I. p. sy6. II p.
faint and peculiar fmell. It readily dries into abrittle femitranfparent fubftance, which looksnot unlike glup, and in drying, it ftronglyadheres to the fubftance on which it refts: fothat advantage is taken of this property tocement together broken pieces of china andother rough furfaces.
Gluten is abfolutely infoluble in water, thoughit muft owe its adhefivenefs and dudliiity to thewater which it abforbs when the flour is firftwetted. Boiled with water it only becomesdenfer, and lofes part of its adhefivenefs. Allthe acids, vegetable as well as mineral, the latterbeing diluted, diffolve it without difficulty, form-ing a clear folution, from which it is againfeparated by alkalies. Strong fulphuric acidblackens and carbonizes it, and difengages fromit an inflammable gas, and converts it partlyto acetous acid, partly to ammonia. Concen-trated nitric acid when cold difengages azoticgas from it, when hot it converts it chiefly intomalic and oxalic acids with evolution of muchnitrous gas and ammonia. a
The alkalies alfo diffolve gluten with eafe.
When gradually heated, without addition, itdries thoroughly, then fhrinks and coils up likemoft other of the foft animal fubftances, thenmelts and takes fire, burning with the fetidodour of animal matter.
In clofe veffels it yields fome ammoniacalwater, and a very brown fetid thick oil inabundance, together with cryftallized carbonatof ammonia and carburetted hydrogen.
In fhort, it exhibits to chemical analyfis allthe properties of animal matter.
Gluten , when dry and kept fo, remains un-altered for any length of time, but if keptconftantly .moift in the ftate in which it wasfirft procured, it flowly alters, lofes much ofits tenacity, becomes fetid and covered with athick white down, and falls into putrefaction.This procefs however is flow, and at the fametime a four fmell is perceivable, and an acid isgenerated which probably corrects and retardsthe proper putrefaction. In this circumftanceit is that it chiefly differs from animal gluten,
M. Cadet 3 has found that gluten after beingkept for many days moift and mouldy is partiallyfoluble in alcohol. Some of this gluten was rub-bed up with alcohol and paffed to the ftate of athick turbid fyrup •, on adding more of the fpiritmuch of the gluten feparated in its original form,but a part remained in perfeCt folution. Thislatter being diluted with water immediatelybecame milky, and let fall a copious white pre-
60. * An. Chim. tom. 41.