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gas disengaged and collected was partly formed observe these ingenious chemists, that it is of carbonic acid, and partly of hydrogen gas. some other substance than sugar which is conSix days afterwards this barley was distilled, verted into alcohol, although sugar is indispenfrom which a product was obtained equal at least sable to its production and to the establishment to one-third of the water employed. This pro- of fermentation. duce, heavier than water, was acid and empyreu- * Two pounds of farina of holted wheat, mixed matic. This acidity demonstrates the conversion with six pounds of water at 140° Fahr., remained of alcohol into acetous acid. The liquor, which six hours without motion. The next day, after was saccharine at the period of distillation, having remarked the swelling of the mass, they was no longer so at the end of the process. placed the matrass upon a sand-bath a little
The same ground and germinated barley, but heated, and added water to favor the disengagedeprived of its bran by bolting, was treated in ment of the gas. We obtained nydrogen gas the same manner as in the first experiment; it twice larger in volume than carbonic acid. The fermented with similar appearances, and yielded vessel, having been taken off the sand-bath, the an equal part of carbonic acid gas and hydrogen temperature having decreased to 57°, the fermen
Thus the bran was not the source of the tation all at once stopped. The liquid, when latter gas, as at first supposed.
submitted to distillation, did not yield alcohol Brewers' mash, exposed in the same apparatus but an acid liquor.' to the same temperature of 72°, fermented more The farina of wheat, therefore, does not form quickly with a more rapid effervescence, and its alcohol by fermentation : yeast is indispensable gas was merely carbonic acid, without hydrogen for this fermentation, although it does not ente: gas. Thus the latter depends upon the farina into the composition of alcohol; by accelerating mixed with flower.
the alcoholic fermentation, it opposes the forma The farina of germinated barley, with water, tion of vinegar. When, on the contrary, the fermenexposed in the matrass to the temperature of tation is very slow, the alcohol becomes acetous 59°, did not ferment until the end of five hours; in proportion as it is formed; perhaps even ther, and its gas was condensed by potash. Upon sugar and the other fermenting substances pas: raising the temperature to 22°, there came off a into the acid state with alcoholizing. mixture of gas not soluble and inflammable, the Air is not absorbed in the vinous fermentation proportion of which was soon equal to that of although its oxygen is in the acetous. Wher. the carbonic acid. Thus it is necessary that wine is manufactured in close vessels it is there should be a heat of upwards of 68° befo stronger, if the process is slower, because a por: there can be any liberation of hydrogen gas in tion of the alcohol escapes from the vats: and the farina of barley which is fermenting.
this is now understood in our malt distilleries. Six pounds of ground barley, not germinated, That alcohol is held in solution in the carbonic treated at three several times with twelve pounds acid which is generated; and thus, it appears, to of warm alcohol, furnished one ounce two intoxicate more rapidly, as is well known in the drachms of pure sugar; while six pounds of wines of Champagne. L'nder pressure, this germinated barley, treated in the same manner, compound is united to the fluid; and, being yielded four ounces and two drachms, or about disengaged, produces the well-known effervesfive per cent. ; which is four times what the bar- cence. The practice of fermentation is partly ley contained previous to germination. Thus regulated by this consideration. The violent germination forms sugar, as we have announced. stage of that process in wine-making is allowed
They put twenty-four pounds of farina of bar- to take place in an open vat; the next is parley, not germinated, into a tub with seven times tially checked by an occasional bung, and, in the its weight of hot water at 158°, and four pounds last of all, the vessel is completely closed. In of mild beer yeast.
Fermentation immediately strong still wines the whole process may be concommenced with great violence, and continued ducted in open vessels; but, in light and brisk seven days. The liquor submitted to distillation, ones, it is absolutely necessary that the last part with the husks, yielded nine litres of a weak and should take place in closed ones. Champagne Empyreumatic liquid, which, being passed again wines are managed so as to ferment even in their through the still, furnished sixteen decilitres of bottles. an alcohol at 16°, which amounts to nine deci- The volume of the fermenting fluid has a conlitres at 40°. These nine decilitres, weighing siderable effect on the process; a few days are twenty-three ounces, and twenty-four pounds of sufficient to complete it when the quantity is barley not germinated, containing only five ounces large. When small, it is difficult to establish, of suzar, it follows, that four times more alcohol and tedious in the progress, and the results are was formed than there was sugar in this farina. also different: wines of different qualities being Lavoisier, however, asserts that 100 pounds of thus produced from the very same materials. It sugar furnish only fifty-eight pounds of alcohol. is the same in the ultimate fermentation or
Twenty-four pounds of germinated and ground ripening of wines. Champagne would be debarley, made to ferment under the same circum- stroyed in a large cask : porter, an extreme case, stances as barley not germinated, presented the is ripened in enormous masses, as are many of same phenomena, and only varied in their pro- the stronger wines. Bulk is peculiarly required ducts. There were two litres 0-3 of alcohol at for the strong and sweet wines; Champagne may 40°, which makes five pounds of alcohol for a be made in a gallon measure. quintal of barley, or three times more alcohol The first appearance is the production of airthan there was sugar; and this answers to the bubbles, terminating at length in a general produce of barley not germinated.
ebullition. The liquor then becomes turbid, a • It must be concluded from these results,' rariety of sclid matters are disengaged, some
filling to the bottom, and others rising to the proportions cannot be expected, either from top of the fluid. The yeast before mentioned nature working at large, and varying in every is thus separated among other matters, while the climate, soil, and situation, or from our most inbulk of the fluid is materially increased. It is geniously conducted experiments. in this stage that we have the power of regulating A perfect fermentation, therefore, has been the extent of the fermentation, by separating the considered an object almost impossible to be floating leaven, or allowing it to return into the obtained; and all we wish to show is, that the liquor. Hence, the process of fermentation in errors of the mixture may be corrected, and the a full cask, ejecting that substance by the bung- whole process improved, by good management. hole.
The common practice, until a few years back, The disengaged gas is carbonic acid chiefly; has been to ferment in open vessels ; ånd though but holding some alcohol in solution. It ap- it was a circumstance well known among chepears, by analysis, that this is the produce of mists, that a certain portion of spirit and flavor part of the carbon of the sugar and of its oxygen; escaped in the form of vapor during the process, and this is the great change which leads to the yet no one had an idea that the condensatory production of the alcohol. But it also contains system could be applied, as it appeared imsome obscure vegetable matter in suspension; possible to effect the fermentation in air-tight because, if passed through water, it not only vessels, being unable to surmount the great converts it into vinegar, but deposits that muci- difficulty which existed of keeping down and lage, which, in vinegar, is called the mother. managing that enormous bulk of non-conis possible, however, that this may itself be a densable gases, which are emitted during the new compound : and it is one which, in certain decomposition of the saccharine matter, and cases, contains azote.
which acquire greater expansive force by the All those juices of fruits which undergo the gradual increase of heat. vinous fermentation, either with or without the The idea, however, occurred to Madame Geraddition of sugar, contain an acid. Vegetable vais, that distillation might be carried on during acids are obtained chiefly from fruits. The the fermenting process. Having come to this apple, for instance, contains malic acid ; the le- conclusion, she proceeded to construct an appamon, citric acid ; the grape, tartaric and malic ratus that would operate in such manner as to acids. The marquis de Bouillon has ascertained return into the vessel the spirit and the flavor that must will not ferment if all the tartar which that was evolved from the fermenting gyle, and it contains be separated from it; but it ferments let out the non-condensable gases, which might, perfectly well on restoring that salt. The same by the increasing heat, acquire too great an chemist ascertained that the strength of wine expansive force, and burst the working.tun. A considerably increased by adding tartar and short description of this apparatus will be sugar to the must. We may conclude from these a fresh proof that the greatest advantages are facts that the presence of a vegetable acid is of often derived from the most simple means. importance in these spontaneous fermentations. It consists of a vessel resembling the head of It deserves attention, that Bouillon obtained more the ancient still, and constructed of such form tartar from verjuice than from wine; and he ob- as to be capable of being placed securely on the served, that the more the proportion of sugar in back, or vat, in which the process of fermentation grapes increased, the more that of tartar dimi- is to be carried on; the back or vat must be pished.
closed air-tight, with a hole in the top, commuIt seems more than probable, from the expe- nicating with that part of the apparatus called riments of Bouillon and Chaptal, that the tartaric the cone, or condenser This cone is surrounded acid is partly decomposed during the fermenta- by a cylinder or reservoir, which is to be filled tion, and that a portion of malic acid is formed. with cold water, so that the alcoholic våpor, or The process, therefore, is more complicated than steam, evolved during the process, may be conwas suspected by Lavoisier. It is obviously densed as it comes in contact with the cold inanalogous to combustion, as is evident from the terior surface of the cone; and, being thereby evolution of caloric and the formation of car- converted into a liquid, trickles down the inside bonic acid, which is a product of combustion. of the condenser, and through a long pipe is reProust has ascertained that, during the fermenta- turned into the fermenting liquor. tion, not only carbonic acid, but azotic gas also, By the application of this apparatus, a conis disengaged. This is a demonstration, that all siderable portion of alcohol, which has been the constituents of must are concerned; for hitherto suffered to escape in the form of vapor, sugar does not contain that principle. Thenard along with the non-condensable gases, is concould detect no azote in the carbonic acid from densed and returned into the liquor; and the
non-condensable gases are carried off by a pipe, We have already seen that a vinous fer- which, proceeding from the interior Inwer part mentation, to be perfect, requires very exact of the cone, and running up the inside of the proportions of mucilage and saccharine matter, cylinder in the cold water, passes out through so as to have the one just sufficient to destroy or the side, and the end is immersed some depth attenuate the other; in which case the result below the surface of water contained in a separate will be, if the operation has been properly con- vessel, permitting the gases to escape, but still ducted, a mixture of alcohol and water, differ- under a certain degree of pressure, the object of ently flavored, according to the materials from which is to confine the alcoholic steam and gas which it is produced, as grapes, pears, apples, within the cone, and allow them a sufficient tiine or malt and hops; but such accuracy in the
to cool and condense.
To obtain a good fermentation, as complete a from the fermenting gyle, the atmospheric air, decomposition of the must or wort, and as per- being lighter, is driven out from the upper part fect a recomposition of alcohol as possible, are of the working tun; and, as no air is permitted the great objects to be obtained. To acquire the to enter afterwards, all the subsequent carbonic former, three requisites are necessary-Huidity, acid gas emitted, diminishes the quantity of heat, and motion; the latter-density, coolness, oxygen contained in the gyle, by the oxygen and tranquillity.
uniting with the carbon as fast as it disunites Let us examine each of these separately; first, from the saccharine matter during its decompoof fluidity.
sition, and thereby secures a soundness and The specific gravity of the liquid most eligi- peculiar mildness, not to be procured by any ble to produce a good fermentation, is between other mode. 1.020 and 1.140, or eighteen, and 132 pounds The necessary conditions for a complete deby Dicas's improved saccharometer, made by composition of the saccharine matter having Joseph Long. Below eighteen pounds of real been stated, it remains to notice those required extract per barrel, the liquid is too thin to pro- for a good production of alcohol. duce a proper fermentation, and above 132 The first already mentioned is a certain denpounds it is too thick; but, supposing the speci- sity, in order to allow the several principles fic gravity of the must or wort to be correct, it which are disunited to recombine. It is doubtmay be carried beyond a proper dilatation by ful whether such a combination will in any case 100 much heat, or congealed to too great a con- take place, until the temperature of the gyle, sistency by excessive cold; consequently either having attained its greatest heat, is afterwards a thunder-storm or hard frost will derange the cooled a few degrees; a fact confirming which is, operation, and are equally injurious to fermen- that a portion of the liquid taken out when at its tation. Any method, therefore, that will ensure greatest heat, and tried hy distillation, produced an even temperature must be of great import- little or no spirit; but such refrigeration must ance; and such a method is obtained by apply- not be effected too suddenly, as it might coaguing the apparatus already described, since, hy late the yet undecomposed mucilage, and check preventing the access of atmospheric air, the its further action on the remaining saccharine sudden changes of the external temperature can matter; and by arresting that natural operation bave no effect upon the fermenting gyle; and if which ought to be pursued a longer or shorter it has been commenced at a proper heat (which period, according to the specific gravity of the is between sixty-five and eighty), will proceed fermentable matter, might produce that result through its different stages, as well during the termed “ropiness,' by holding in solution the coahottest days of summer, as in the selected months gulated mucilage. of autumn and spring.
Here again the apparatus will be found of With respect to motion, we are indebted to great service, for, hy frequently renewing the M. Gay Lussac, as we have already stated, for a cold water in its reservoir, the internal temperabeautiful and important experiment, proving ture will gradually diminish hy the heat of the thut must, possessed of all the requisites to pro- gyle coming in contact with the cold interior of duce a good fermentation, will not begin to fer- the cone: but, in order to effect this, the tranment unless excited by a foreign agent. He quillity above mentioned is necessary, since the placed the must in a close vessel, from which continual motion is caused by the oxygen solithe atmospheric air had been exhausted, where citing new combinations with the carbon, and it remained several days without giving any thereby constantly giving rise to a fresh supply signs of fermentation, from which he concluded of heat. some power was wanting to break the union of Besides the advantages already mentioned, its constituent principles; he therefore introduced which are common to all fermented liquors, a small quantity of oxygen, which immediately there are others peculiar to each, that require to caused the must to ferment, evidently proving be explained. the necessity of a small portion of atmospheric The apparatus being applied to ferment the air (which contains oxygen), to allow the fermen- must of grapes, has been found to procure an
But it at the same time increase of quantity, amounting in some instanproves, that, after performing that office, this ces to ten or twelve per cent., and which necesgreat enemy to all fermented liquors may be dis- sarily varies according to situation, season, or pensed with, without impeding the process; as former management; but in no instance has it the small quantity of oxygen, introduced by M. been found less than om five to six per cent. Gay Lussac, was soon absorbed by the carbon When applied to the fermentation of beer, to form carbonic acid gas, and he found no oc- this saving has constantly been between four and casion for any further supply.
a half and five per cent., a quantity certainly inThis discovery is of the greatest importance, ferior to that obtained from wine, but which will since it enables us, without the least detriment not appear unimportant when it is considered or inconvenience to the process, to exclude the that this saving is a spirit congenial to the nature oxygen of atmospheric air, which, by constantly of the beer, and an essential oil necessary to its supplying the gyle with the principle that causes preservation; in addition to the peculiar mildand promotes acidity, casts on it from the first ness and superior flavor. that roughness and disagreeable favor which Mr. Henry found, by a series of very interestspoil most of our common beverages.
ing experiments, that malt infusion might be liere again the new apparatus proves of great made to enter into complete fermentation by benefit. for, as soon as carbonic acid gas is evolved impregnating it with carbonic acid, prepared
tation to commence.
from chalk and sulphuric acid, and the liquor but every substance susceptible of the vinous thus fermented gave a yeast which made per- can likewise pass into the acetous fermentation; fect bread, gave alcohol by distillation, and hence, sugar dissolved in water, sweet vegetable vinegar by further keeping. The wort itself juices, or infusions of grains that have been undoubtedly contained all the ingredients of malted, can be converted into vinegar. Fecula, yeast, since this substance was produced during even without the previous process of malting, is the fermentation ; but the experiment is decisive equally susceptible of it; for, in the process of to prove that no addition of azotic extract is re- starch-making, a quantity of vinegar is formed, quired to begin fermentation in materials naturally not merely from the small ion of saccharine fermentable, though, when once begun, the yeast, matter in the grain, but likewise, as Vauquelin, as fast as it was produced, must have assisted in in his Analysis of the Sour Liquors of the the fermentation then going on. The evidence Starch-Makers, has remarked, froin the fecula for the necessity of an acid to begin fermentation itself. Even substances which are not at all is, therefore, more decisive, but it is still doubt- susceptible of the vinous fermentation, it appears. ful whether any particular one is required, or to be established, may suffer the acetous. This whether there are not several which will answer is indeed contrary to an opinion formerly mainthe purpose. In Mr. Henry's experiments the tained, which regarded the acetous merely as a acid employed was the carbonic, and, from the continuance of the vinous fermentation, and as arrangement of the apparatus, probably a small necessarily preceded by it. But it often happens portion of sulphuric was also carried'in along where the former cannot be traced, and where with it. But in grape juice there is no proof of there is no reason to suppose that it ever did exist, the existence of carbonic acid ready formed, as in vegetable juices or infusions containing though the tartaric, malic, and other vegetable much mucilaginous with scarcely any saccharine acids contain within themselves the ingredients inatter, which soon become sour; and the sourof carbonic acid, and are chiefly and ultimately ness which even pure mucilage, or a solution of resolvable into this acid. Yeast will ever induce gum in water suffers, is probably owing chiefly fermentation after it is pressed and dried into to the production of acetous acid. solid cakes (a practice not uncommon, as it will Nor is pure alcohol, in any state of dilution keep for a great length of time in this form), with water, capable of undergoing the acetous but after this operation it can hardly contain any fermentation : there must always be present carbonic acid ready formed, though with abun- other vegetable principles, as sugar, mucilage, or dant tendency to reproduce it by the first mutual farinaceous matter. Even a certain proportion action of its constituent parts.
of these is requisite. Hence strong wines do The attenuation of liquors, or the diminution not become so readily sour as weak or sweet of their specific gravity by fermentation, is very wines; for the same reason, wine that has been striking. This is shown by the hydrometer, clarified is less liable to ferment; and strong which swims much deeper in fermented liquor, wines can be made to pass into the acteous ferthan in the same materials before ferinentation. mentation more easily, by adding to them sugar Much of this attenuation is, doubtless, owing to or mucilage; and, when these highly spirituous the destruction of the sugar, (which, dissolved in wines are thus made to ferment, they furnish a water, adds to its density), and to the consequent much stronger vinegar than those which are production of alcohol, which, on the contrary, weak. Even the vegetable acids appear to conby mixture with water, diminishes the density tribute to it, and, in the conversion of sweet of the compound. The extract, or mucilage, also vegetable juices or of wine into vinegar, there is appears to be in some degree destroyed by fermen- reason to believe that the malic and tartaric tation, for the gelatinous consistence of thick acids they contain are partly changed and pass liquors is much lessened by this process: the into the acetic acid. destruction of this principle, however, is by no
The addition of some substances which act means so complete as of the sugar, many of the as ferments, appears also to be requisite. It is full-bodied ales, for example, retaining much of true that wine and other fermented liquors will their original clamminess and gelatinous density of themselves become sour in a certain time; even after having undergone a very perfect fer- but this is probably from their containing a por
tion of matter analogous to ferment, and which The acetous fermentation must now be noticed. excites the change. In preparing vinegar, it is When any of the vinous liquors are exposed to known that a certain quantity of such matter the free access of atmospheric air, at a temper- must be added, either a portion of the substance ature of 80° or 85°, they undergo a second fer- which has been deposited from a liquor that has mentation, terminating in the production of a previously passed into vinegar, or a quantity of sour liquid called vinegar. During this pro- yeast; and there is every reason to believe, that cess, a portion of the oxygen of the air is con- it is vegetable gluten which is the essential verted into carbonic acid; hence, unlike vinous principal of these ferments. Fourcroy and fermentation, the contact of the atmosphere is Vauquelin accordingly found, that, when sugar necessary, and the most obvious phenomenon is was added to water which had stood over the the removal of carbon from the beer or wine; gluten of wheat, it quickly formed vinegar; and the vinegar of this country is usually obtained Berthollet obtained the same result from a mixfrom malt liquor, while wine is employed as its ture of gluten and starch. This principle, Vane source in those countries where the grape is quelin remarks, contributes to the formation of abundantly cultivated.
vinegar in the liquor formed in the manufacture Not only do vinous liquors suffer this change, of starch; and the matter which is contained in
common vinegar from malted grain, and which tion of carbon than the fixation of oxygen; leaving renders it so liable to putrefaction, is, according of course, however, a larger proportion of the latter to the chemist, vegetable gluten.
priuciple in the composition of the acetic acid. The admission of atmospheric air is essential This simple view cannot however be received to the acetous fermentation. Hence, wines that as altogether just, since alcohol alone cannot are well bottled may be kept for a long time un- undergo this change, nor can it by oxygenizement injured, and the more free the exposure to the be converted into acetic acid; and since the preair is, the sooner they become sour. The oxygen sence of mucilage, saccharine matter, or other of the air is at the same time always absorbed. principles, is always necessary to the acetous According to Saussure, this oxygen is not ab- fermentation, the operation of which is not exsorbed so as to enter into the composition of the plained in conformity to his theory: neither does acid, but is expended entirely in abstracting it explain the action of the ferment which apcarbon, and of course formning carbonic acid. pears to be nearly equally indispensable. It In keeping wine in contact with oxygen gas for will afterwards appear, that nitrogen probably a year in receivers closed with mercury, he found enters into the composition of acetic acid ; and it converted into vinegar; but the diminution of the operation of the ferment may be partly that the volume of the gas never exceeded, but was of affording this element. always inferior to the volume of the wine; and Vinegar, the product of the acetous fermentahence, acording to the view he gives of the ex- tion, is prepared in different countries from difperiment, the oxygen had combined with carbon ferent materials. Where the grape is cultivated, so as to form carbonic acid, which had been ab- it is obtained from weak or spoiled wine. This is sorbed by the liquor. And accordingly he found, kept in a proper temperature with the access of that when he made the experiment with wine the air, and the fermentation is excited by the previously impregnated with carbonic acid gas, addition of a quantity of the sediment of vinegar, this wine, under the same circumstances, was of wine already sour, or of the lees of such wine. equally converted into vinegar, but without the The product is stronger in proportion to the volume of the elastic fluid above it being previous strength of the wine. In this country it is changed; the oxygen consumed being replaced prepared either from unrefined sugars, or from by an equal volume of carbonic acid gas. the wort obtained by infusion froin malted
A certain degree of temperature is requisite grain ; the fermentation being exc.ted by yeasi, to the acetous fermentation. It takes place and being carried on in a warm apartment. slowly, even below 60°; but it proceeds with This vinegar is in general inferior in strength more rapidity between 60° and 80°; and in and purity to that from wine, and is more liable forming vinegar artificially, the temperature is to become mouldy or suffer the putrefactive ferkept high. If it fall below 500 it is nearly mentation. This appears to be owing chiefly to checked; and hence wines can be longer pre- the presence of glutinous matter ; and hence the served by being kept below this temperature. rationale of the method which Scheele pointed
The phenomena which occur in the acetous out as the best for preserving vinegar, that of fermentation are somewhat analogous to those in heating it, and bringing it even to boil for a few the vinous. When it is proceeding rapidly, there minutes, the glutinous matter being separated by is an intestine notion, not accompanied, how- a kind of coagulation. ever, with such a disengagement of elastic fluid Panary fermentation has already been noticed us in the vinous fermentation; the liquor is under the article Bread, and little more than turbid; its temperature rises; and its smell be- the theory remains to be examined. · Although comes perceptibly acetous. These appearances the fermentation of dough has been termed paat length subside, and the liquor gradually je- nary, there is little doubt but it is merely a mocomes clean, having deposited a kind of glutin- ditication of the acetous. The subjects of both ous sediment somewhat similar to yeast. species of fermentation are certainly different, in
The theory of the acetous fermentation is not regard to consistency; but it is probable, that yet completely elucidated. Since the strength of the modification alluded to is the consequence the acid which is formed from it is proportioned of this difference: for the fermentable matter, to the quantity of alcohol, or of matter of a compo- from want of room for action, does not arrive at sition analogous to alcohol, and in general capable the same point of chemical change which it of passing into it: and, since this alcohol disap- would do in a more diluted state. We shall pears during the fermentation ; Lavoisier sup- not attempt to theorize on the changes which posed that the theory of the process might be take place during the panary fermentation, fur inferred from the changes which this principle can ther than to suppose that the flour, yeast, and be supposed to suffer : and, as he found that water, give out their elementary components for during the change oxygen is absorbed, while the formation of saccharine matter, starch, carscarcely any sensible quantity of carbonic acid is bonic acid, and acetic acid; and that, during the extracted, he concluded, that the acetous fermen- incipient generation of the latter, the process is tation consists in the oxygenizement of the al- stopped by the action of artificial heat.
If the experiments of Saussure be ad- The fermentation that produces putrefaction mitted as correct, in proving that as much car- is the last stage of this process The most rebonic acid is formed as corresponds with the markable changes produced upon a body by quantity of oxygen consumed, this acid being re- putrefaction are upon its color, smell, and taste. tained by the liquor, the theory of Lavoisier would Flesh beginning to putrefy, is well known to require to be so far modified as to ascribe thee hale very soon after a penetrating fetid smell, change of alcohol into vinegar rather to the abstrac- t coiwr becomes pale, thea inclining to blue