94
FERMENTATION.
Pcctic Fermentation. —Pectic acid may be obtained from the expressed juice o erots, and it seems to be formed in the process of extraction by the reaction of »*" ^ f -ein the carrots upon a substance called pectine; a transformation analogous therwith that which takes place in the formation of the essence of bitter almonds. t isGallic Fermentation. —Gallic acid does not exist ready formed in nut-galls, c dgenerated from their tannin when they are ground, made pasty with water, and j,ol,to the air. This conversion may be counteracted by the red oxide of mercury, a oxa lic,sulphuric, muriatic, and nitric acids, bromine, essence of turpentine, creosote, ^gs-acetic, and prussic acids. The tannin disappears in the sequel of the above me 1phosis. . 0 tlier
Fatty Fermentation. —All fats are transformed by the action of an alkaline o ^ sbase into certain acids, the stearic, margaric, the oleic, ethalic, &c. When tbes juj.are once formed, they can not by any means, hitherto known, be reconverted into jj^geitive fat. By the fixation of water in the acid and the base (called glycerine), a . (se lf tois effected which can not be undone, because the glyceric base is incapable by aeC es-displace the water, once combined in the hydrated fat acid. The circumstances c0 .sary to the fatty fermentation, are like those of other fermentations; namely, fl g(joperation of an albuminoid matter, along with water, and a temperature of fromF.; under these conditions, the matter becomes warm, and assumes speedily the wh’! eter of rancidity; acid is generated, and the carbonate of soda can then form sa ^ jnthe fatty acid is liberated; a circumstance impossible when the fat wasthe neutral state.. This altered fat, treated with water, gives up to it gly cer } c . f^tvff cSDigestive Fermentation. —Digestion of food may be considered in its essentiaas a peculiar fermentative process. The gastric juice is a genuine ferment- afl“
' Gmelin, and Prout, have shown that the gastric juice contains muriatic withEberli has made interesting experiments on the digestion of food out of the y c o»'water containing a few drops of the same acid. He observed that when this t nts pinlained none of the mucous secretion of the stomach, it did not dissolve the a &eg tce \into it; but with a little of that mucus it acquired that property in an ennnc duc e “Even the mucus of the bladder had a like effect. Schwann and Vogel havel a hiii>'this digestive principle in a pure state, called by them pepsine, as obtained se pai^ edantly from the stomachs of swine. The glandular part of that viscus being jyltefrom the serous, is cut into small pieces, and washed with cold distilled w* ^ Th 1digestion for 24 hours, that water is poured off', and fresh water is P oure ,rj, eoperation is repeated for several days, till a putrid odor begins to be felt. , e ciP* .i.infusion thus obtained is precipitated by acetate of lead. This white flaky R xe d ivdcontains the pepsine, accompanied with much albumen. It is then washed, - B g » 0 .water, and subjected to a stream of sulphuretted hydrogen. The whole ^ sothrown on a filter, the coagulated albumen remains on the paper, along| " y, V _pliuret of lead, while the pepsine liquor passes, associated with some acetic 0 f ca rl ^ ethis liquor a very small quantity of muriatic acid be added, it becomes capa ab°'ing on artificial digestion. Dry pepsine may be obtained by evaporating.^ B bsoldfiltered liquor on a water bath, to a syrupy consistence, then adding c0 nsti ,ualcohol, which causes a bulky whitish precipitate. This dried in the a oV ed c .° e jpepsine. It contains a minute quantity of acetic acid, which may be * enpletely, by heating it some hours on the water bath. The white powder t0 V<fe ^is soluble in water, and betrays the presence of no acid whatever. ^ cc ° 2 ^.o 9 ; oX ^ndthis substance is composed of, carbon, 57-72; hydrogen, 5-67,- azote, e psin e&c., 15.52 = 100. Vogel has proved the analogy between the action o ^js
diastase by the following experiment:— ■ • l nd P ut in *° tt> e
He dissolved two grains of pepsine in very weak muriatic acid, a ho urS u s .
liquor heated to 81° F., small bits of boiled beef. In the course ot a corn pietely ^pieces became transparent on their edges, and not long after they ' ver< t n renin*, fiotf
solved. He now added fresh morsels in succession, till those last pu Jn
changed. He found by analysis, that 1-98 grains of the pepsine ^ er ^ cC | digest! 011 ' aJt yminute a portion of this ferment was necessary to establish and * jj on with° afact, we may infer that pepsine, like yeast, serves to accomplish dt? .waste of its own substance whatever, or probably with its multiphca 0 f the r isRennet, with which milk is coagulated in making cheese, is some digesting ^nature as pepsine. It has been called chymosine. But the simpl es
the following:— ' niuri 3 * 1 ?
If 10,000 parts of water by weight be mixed with 6 parts of or w bite oand a little rennet, a liquor is obtained capable of dissolving hard non a
beef, gluten, &c., into a transparent jelly in a few hours. conversing tfe
Ammoniacal Fermentation .—Under this title may be described the ^ a fav»into carbonate of ammonia under the influence of water, a ferine ,temperature. Urea is composed in atoms; reckoned
BCi“