One part of hydrogen is sufficient to saturate and fix above five of carbon, and they require nearly sixteen parts of oxygen to complete their formation into alcohol, while the water of dilution undergoes a proportionate decomposition and recomposition, to assist the resolutions and combinations, and support the admirable equilibrium preserved by nature.
At the same time that the extreme levity of the hydrogen gas accounts for the great quantity of heat which it holds in combination, and the high temperature requisite to effect its decomposition, and that such is its capacity for heat, that though combined with oxygen and water, it still possesses the property of absorbing a great deal more. It is this property that renders aqueous vapour lighter than atmospheric air in which it ascends; yet we have just now demonstrated the resolution and combination of hydrogen gas, and oxygen gas, both extricated from the fermentable matter and the water of dilution, and their formation into spirit, &c., at a temperature not many degrees above that of the incumbent atmosphere, and no higher than that excited by respiration in the animal system.
In which we have shown the vegetable oxyde, (saccharine matter,) when reduced by the admixture of water, to form the worts or wash, to be a carbonated hydrogenous fluid, containing the elements of wine, beer, ale, spirit, &c., and the mode of producing them under circumstances conducive to their formation; these are motion, heat, pressure, and mutual attraction, called into existence by a species of low combustion, or fermentation, somewhat similar to respiration. In which the materials, the products, and the liberation of caloric are ultimately the same, whether the operation is attended by visible fire from the velocity of action, or weak incalescence from the slow progression of its motion; in which the component elements are continually assuming a gasseous form, and as constantly losing it by the force of mutual attraction for each other. No sooner is the equilibrium broken, in one instance, by their gasseous appearance, than it is restored by their condensation, and the heat liberated by the latter taken up by the former, by which the equilibrium is preserved; in this consists the increase of temperature above that of the surrounding atmosphere, accompanied by the discharge of fixed air; to fix, and advantageously apply which, shall be the next consideration; and, by an accurate imitation of the modification employed by nature, to render the fermenting fluid so much the stronger by such fixation. To accomplish which, we must advert to what has been delivered in the preceding pages, particularly to the proportions in which the equilibrium preserved by nature consists, and exactly to her manner of combining them in sugar, malt, and other saccharine matter, her mode of breaking this equilibrium, or decomposing them by fermentation, and recombining them into wine, beer, &c., and by the same process restoring the equilibrium.
It cannot be doubted, but that, in the investigation of the acetous process of fermentation with the attenuation we do the vinous, they will mutually reflect light on each other; in which it will come out that wine, beer, ale, vinegar, spirit, &c., are not the only commercial preparation to which the doctrine of fermentation, or low combustion, may be advantageously applied, but also to others, that are perhaps equally important and productive.
The cleansing being at the meridian, or greatest temperature of the heat of the fermenting fluid, and the object of that cleansing being to reduce the heat, and thereby allay the violence of the fermentation, by which an immediate decomposition takes place, the lighter impurities buoyed up to the top of the fluid flows off with the yest, while the heavier dregs descend to the bottom, and the fermentation gradually declines as the cleansing draws to a conclusion, and the fermenting fluid forms a turbid heterogeneous mass, very perceptibly approaching towards a transparent homogeneous fluid in its progress to a drinkable state.
In laying out a brewery, the air should have free access to the coolers on all sides, under and over; cleansing vessels should be similarly situated, and, if avoidable, the coolers should not lay immediately over them, to raise their temperature, which should not be many degrees above that of the atmosphere, at temperate, which is fifty-two degrees; but the descent from the cleansing heat (seventy-five to eighty-five) should be progressive, that is, not sudden. A sudden chill would precipitate the grosser, and diffuse the lighter dregs throughout the fermenting fluid, which should be thrown off from the surface in cleansing; this would retard the fining, and empoverish the beer or ale; while the mode recommended will be found to promote transparency, and give strength and body, that is, fullness and spirituosity. In general, the cleansing commences too soon for the strength and quality of the goods, particularly for porter, since the introduction of a greater proportion of pale malt than formerly used; a more perfect fermentation is now requisite to keep up the genuine distinction in that flavour of porter from ordinary beers and ales, which, since the change of lengths, has much declined, though the only characteristic quality that gives it merit over other malt liquors—an object that deserves consideration in this great commercial branch of trade, and source of national wealth, where the loss of distinction will be the loss of trade. The rough, astringent, thirst-creating smack is the produce of the brown malt, and a well conducted fermentation. The porter now brewed can no more bear the sudden chill of a cooling atmosphere in the barrel cleansing, without too immediate a condensation and separation of its parts, than it is able to sustain the quick changes of a warm atmosphere, without an immediate tendency to acidity. As things now are, either extreme can only be avoided by a more attentive advertence to the mode of cleansing, so as to prevent a predominant tendency to either by adopting the means proposed, or such other, on the same principles, as are equally likely to preserve the quality, increase the strength, promote transparency, and avoid acidity. I know it may be urged by the most able brewers, that a high and rapid fermentation in the cleansing is a principal cause of that flavour for which porter is distinguished; that this kind of fermentation leads to a more perfect attenuation; and some of them may, with great truth, add, a perfect attenuation is the genuine mode of early bringing beer forward. This I most readily grant; it is the doctrine I wish to inculcate. The greater gravity of keeping beers, preserves them in a mild state, while their spirituosity prevents acidity. The flavour of the colouring matter now in use, nor the change it induces, is not, by any means, adapted to preserve the genuine flavour of porter, or compensate for that made in the change of malt; a change I by no means condemn, with respect to the malt; but however advantageous to the length, we must not altogether give up flavour, while we may equally as well, and indeed much better, preserve both by a due admixture of each sort of malt, and with suitable additions and proper correctives in the process or preparation of porter, both salubrious; as by the subsequent mixture of stale and mild beer, before sending out, or, afterwards, by drawing them from different casks into the same pot, when on draught, to suit the palate of each respective customer.
I hope it is by this time understood, that my views are to raise the Process of Brewing above the vulgar error that tyrant custom has entailed on it, and by the free exercise of the brewer's abilities, both in a scientific and tradesman-like manner, so as advantageously to preserve flavour and quality, with almost any proportions of every sort of malt he may occasionally be obliged to use.
The world is continually exclaiming that experience is better than theory. This is very true; for example, he who has had a very long experience, may, in general, perform operations with tolerable exactness; but this he undeviatingly does by certain stated means, without any deeper intelligence of the process. I would, with Mr. Chaptal, compare such a man to a blind person who is acquainted with the road, and can pass along it with ease, and perhaps even with the confidence and assurance of a man who sees perfectly well, but is at the same time incapable of avoiding accidental obstacles, of shortening his way, or taking the most direct course, and alike incapable of laying down any rules which he can communicate to others. This is the state of the artist of mere experience, however long the duration of his practice may have been, as the simple performer of operations.
Brewing, fermenting, distilling, &c., are branches of commercial chemistry, that generally challenge the attention and secure the protection of those governments that constitute them sources of revenue and trade. Chemistry is as much the basis of the arts and manufactures, as mathematics is the fundamental principle of mechanics. In the process of brewing porter, ale, threepenny, &c., to be subsequently treated of, the practical minutia of fermentation and attenuation shall be circumstantially laid down in each, so as to account for, and distinguish the variety of flavour, &c., assignable to each cause effected by the different modes of treatment.