twenty-five pounds per barrel of fermentable matter being attenuated,
and have even in that quantity included five pounds eight ounces of
lees and yest, (the least quantity produced,) such calculation must not
be admitted to preclude the practicability of attenuating almost every
particle of fermentable matter, and replacing it with an equivalent
particle of spirit, if that spirit which is now carried off by the
avolation of the fixed air, is, agreeably to my proposal, either
arrested in its flight, or filtered, after its escape from the guile
tun and cleansing vat, by the proper apparatus.
Having in a former part of these papers observed, that attenuation may
be carried too far, it may be necessary for me to reconcile these
seemingly opposite positions, which should be understood in this way:
When the quantity of fermentable matter, suspended in a barrel of
worts, intended for beer, or ale, is from five to ten pounds more than
twenty-five pounds per barrel, every particle of it may be safely
attenuated, as the quantity of spirit generated will be sufficient to
preserve the beer, or ale, for any requisite length of time, provided
it has been properly hopped, &c., or in lieu thereof, received certain
other additions to improve its vinosity, strength, and keeping; when
the quantity of fermentable matter in worts is from five to fifteen
pounds per barrel less than twenty-five pounds, the height of the
attenuation ought to be limited on keeping beer and ale; the spirit
generated being insufficient to preserve so much fermented fluid in a
drinkable state for any length of time, with the usual additions only,
even during the summer heats of our own climate; and if so, it is
totally unfit for either exportation to warm latitudes, or for keeping
at home.
For the right understanding of these observations, we should consider
that the unattenuated fermentable matter is perpetually furnishing a
gradual supply of fixed air and spirit, by means of the imperceptible
fermentation always going on in vinous liquors.
Weak beers and ales fret and spoil very soon in warm weather, which
proceeds from the development and avolation of their fixed air; strong
beers and ales have their limits under the same influence of heat,
time, change of the atmosphere, &c., and owe their preservation to two
things, viz. to a due proportion of fermentable matter unattenuated, or
the quantity of spirit they contain; as under these circumstances they
are either preserved by the spirit already formed, or that continually
supplied by the spontaneous decomposition of the fermentable matter
they contain, slowly developing and yielding a fresh supply of air and
spirit; hence beer and ales, not too highly attenuated, derive strength
and spirituosity from age, when properly stored or cellared, and duly
secured from the changes of the atmosphere.
These observations are applicable to sweets, or made wines, and to
those which are the produce of the grape, the progress of fermentation
and attenuation being (or ought to be) interrupted in them by racking
off, which is similar to cleansing in beers and ales: and in Madeiras,
and other dry wines, the incipient acidity is corrected and restrained,
by proper additions introduced in the early part of the process, and
with others of similar effect when the wines are making up, either for
use or exportation.
We may gather from these observations, that worts attenuated for beer
or ale, to the decomposition of all their fermentable matter, that is,
attenuated so high, or so low, that their specific gravity is reduced
to the standard of common water, and from that to the degree of levity
spirit is known to give to water, in the proportion to the quantity
added, and left to the preservation of the spirit formed, they have
little or no auxiliary assistance from their original products, already
exhausted by the highest or completest attenuation obtainable; an
important circumstance, always to be attended to, particularly by those
who affect an unnecessarily high attenuation!
The intelligent brewer may, by the assistance of these observations,
form a most accurate rule for the regulation of his future conduct in
the management of fermentation, according as his beer or ale is to
be weak or strong, or for present use or long keeping; for the
accomplishment of which, the use of the hydrometer and thermometer
claim his peculiar attention, and will undoubtedly answer his
expectations, when joined to the certainty he is now at, of knowing
when he is, or is not, to expect the development of fixed air and
additional spirit, by which he can govern himself accordingly.
These observations lead to a removal of the difficulties that lay in
the way, and, at the same time, suggest a mode of applying the present,
or of constructing a future _hydrometer_, for ascertaining the strength
or the quantity of the vinous spirit in beer, wine, ale, and other
fermented fluids, which has long been a desirable object.
The distiller, having none of these niceties to attend to, is governed
by the ultimate extent of the attenuation the worts, or wash, is found
capable of, and which is both assisted and protracted by its superior
density, in its progress from specific gravity to specific levity, if
such an expression is admissible.
Fermentation, begun in a fluid more or less saturated with saccharine
or fermentable matter, the process is finished sooner or later, and
usually in proportion to the degree of saturation, and the being
conducted with more or less vigour under a well regulated temperature;
for the more a fluid abounds with this matter, the grosser and denser
it must necessarily be, and the longer will the attenuation be
protracted; the longer it is protracted, in air-tight vessels, and in a
healthy and vigourous state of decomposition, the more spiritous and
strong will that wash turn out, and the greater the produce of spirit
in distillation; hence, it is both protracted and assisted by its
density.
A languid may be truly called an unhealthy decomposition, it being
productive of diseases common to misconducted fermentation, acidity,
putridity, and lack of spirits, with a tendency to precipitate and burn
upon the bottom of the still; hence, all the decompositions are
confounded together, as in spontaneous fermentation.
The formation of acidity during the process, is not of that injury to
the distiller that it is to the brewer, nor is this recent acidity
vinegar, as has been supposed by some chemists, but the incipient state
of combination of resolving elements, whose particles are in that
juxtaposition best suited to absorb developing hydrogen in a nascent
state, and intimately to combine with it into vinous spirit, the
approximation to which is promoted by time and incumbent pressure:
these positions shall be explained as I proceed.
The reason that putridity is so rarely discovered in excited
fermentation, is, that it is usually counteracted by the previously
evolved acidity, and corrected, but not saturated or neutralized; for,
were that the case, the putrid could not immediately succeed the
acetous process in the same fluid, nor exist together, as they are
known to do in declining beer, vinegar, &c.
The reason that acidity is not more frequently observed and attended to
than it is, is because of its being sheathed or covered by the
unattenuated sweets, or fermentable matter of the wash that remains
undecomposed.
On the other hand, when acidity is very prevalent, it may be mistaken
for unattenuated fermentable matter, acidity increasing the density and
specific gravity of the fluid.
Putridity, from the avolation of its products, promotes levity, and
that in proportion as its increase surpasses that of the general acid;
and it is not until the action of the acetous becomes languid, that the
putrid process gains the ascendency, when it is then difficult to
overcome.
Although these observations may show how the hydrometer, or its use, in
unexperienced hands may be baffled, they both distinguish and explain
the value of its application; they do more--they elucidate the doctrine
of fermentation, and illustrate the goodness of Providence, who has
made nothing in vain, but provided nature with its own resources for
conducting every operation in the great plan of the universe with
uniform and unerring security.
In the decomposition of fermentable matter, either by combustion or
fermentation, (which I have defined to be synonimous,) a portion of
inflammable air, or hydrogen, is first evolved; secondly, another
portion of inflammable air, united with pure air, or oxygen gas,
evolves under the form of fixed air; this is the constant and uniform
phenomena of these decompositions, and are progressively going on from
the beginning to the end of the fermentation, while there is any
fermentable matter to attenuate. A due portion of oxygen uniting in a
nascent state with a correspondent portion of inflammable or hydrogen,
and fixed air, forms the spiritous particles dispersed through the
fermenting fluid, which create vinosity, and constitute it wine, beer,
or wash.
During which, so great is the avolation of fixed air, (as we have
seen,) that much of the ethereal part of the new formed, or, rather,
the scarcely-formed spirit, is carried off with it in a gaseous state.
This is much assisted by the agency of the atmosphere, which is the
solvent and receptacle of ethereal products, whose affinity for them
must be as great as it is perfect and immediate--which demonstrates the
necessity of having air-tight vats. When we consider the composition of
the atmosphere, and that it owes its formation and existence to this
cause, and, thereby becomes the menstruum of all created matter, we may
be better able to understand the composition and formation of vinous
spirits, and, by closely copying the original, more successfully
imitate nature. We have seen that the principal phenomena in fermenting
fluids is a brisk intestine motion of their parts, excited in all
directions with a loss of transparency, or a muddiness, a hissing
noise, the generating of gentle heat, and an exhalation of gas. This
heat, we must now observe, is always very sensible before the
extrication of any gas. We have adverted to the similarity existing
between respiration and fermentation, which is remarkably so in the
equality of heat produced in both in a healthy state of either, and
which seldom exceeds ninety-six degrees of Fahrenheit's thermometer;
but there are instances of their being much higher in both, without
producing much injury to either. Instances of this could be adduced at
home, without referring to warmer climates of the East and West Indies,
where the temperature of the atmosphere is so much higher than with us;
and that the temperature of the fermenting fluid, when at its height,
always exceeds that of the surrounding atmosphere in these latitudes,
which makes the similarity still stronger between these two decomposing
processes. This is a general and just remark; but, in order to regulate
it by practical facts, we must name the medium standard of heat, which
rarely exceeds eighty-five degrees with the brewers; this is the medium
of seventy-four and ninety-six degrees; but the medium heat is not
unfrequently up to ninety-six degrees in the distiller's fermenting
backs of Great Britain. Much depends on the degree of temperature the
fermentation is pitched at: here, nothing is spoken of but the
cleansing heat with the brewers, and the medium heat with the
distillers.
For the maintenance of combustion, the free access of air being
necessary, an objection may be raised to air-tight vats, as unfit to
carry on this process in, to the exclusion of external air; which
objection may seem to gather force from the compression it occasions of
the fixed air on the decomposing fluid, which is allowed to extinguish
active combustion. I must acknowledge these are formidable objections
to my definition of low combustion, but I by no means find them
unanswerable.
The aptitude of new hay, malt, and other vegetable matters, to
spontaneous combustion, when impacted together by incumbent pressure,
and a certain degree of moisture, should be recollected; and that this
tendency is not destroyed by excluding the admission of external air,
but by quickly cooling and dividing the impacted hay.
The great quantity of oxygen, or vital air, both in the water of
dilution, and in the fermentable matter, with which the fluid is more
or less saturated, should be also recollected, which is about
eighty-five parts in the former, and sixty-four parts of one hundred in
the latter.
Though, in an unelastic or fixed state, it is one of the properties of
combustion to disengage and render it elastic, great part of which,
during the low combustion which it supports, and in which heat is
visible or perceptible, and light in an invisible state developed,
three parts of this oxygen, with about one third of its weight of
carbon, is converted into an elastic state, under the form of fixed
air, that separates from the decomposing mass; a circumstance attending
also on the combustion of coal and other combustible substances during
their decomposition by that process, which supported in them by the
external air of the atmosphere, where heat and light are both visible
from the intensity and velocity of the combustion; and wholly invisible
in the former, not from exclusion of external air, but from the length
of time elapsed in low combustion; the one being performed
instantaneously, and the other taking several days from its
decomposition. Although fixed air is known to extinguish a lighted
candle, and destroy animal life, that is, to be equally unfit for the
combustion of inflammable bodies, or the support of animal respiration,
it is also known to be as successfully employed as atmospheric air, or
even dephlogisticated air, to melt glass, &c., when applied to the
clear flame of a wax candle, by passing a current of it through a
blow-pipe, to direct that flame on the glass to be melted.[4]
[4] Count Rumford on the Economy of Fuel.
This will not be so much to be wondered at, when we consider that the
proportion of vital air in fixed air is as twenty-seven to nine, and in
atmospheric air, the proportion of azotic gas or phlogisticated air, to
vital air, is as seventy-three to twenty-seven; therefore, the former
contains three fourths of vital air, and the latter little better than
one fourth; but the fixed air is in a combined, and the phlogisticated
air in an uncombined state. Among the processes made use of by nature
for the decomposition of vegetable and animal substances, fermentation,
or low combustion, is a principle one. Air, in a fixed or unelastic
state, may be as necessary here as air in an elastic state is known to
be in the active combustion of inflammable bodies. Chemists and
philosophers are no strangers to two sorts of combustion, one in
external air, and the other in close vessels.
But this is not the combustion alluded to in fermentation, where all
the requisites for complete decomposition is to be found independent of
contact with the atmosphere; here one part is oxygenated at the expense
of the other, and the other disoxygenated in favour of it.
Nor does the solution, or decomposition of metals by acids, the
combustion of inflammable and vital air for the production of water,
stand in need of external heat or fire, any more than the low
combustion in which fermentation consists for the production of spirit,
beer, or wine, than that generated by the self-operation of its own
temperature; similar to this is the self-animating principle or power
with which nature has endowed the animal body of generating its own
heat by respiration.
In fermentation, the caloric, or matter of heat, which is plentifully
disengaged by the condensation of oxygen, is prevented from breaking
out into flame with the condensing hydrogen, from the presence of
affinities in the fermenting mass, ready to absorb and fix them into
vinous spirit, ale, beer, &c., with the other component element,
carbon; by which they are too instantaneously taken up and fixed, to
amount to more than bare ebullition, and pass at once from an incipient
state of elasticity, to a fixed and non-elastic one, while the
redundant heat, which would otherwise appear, is taken up and carried
off by the abundant formation of carbonic acid gas, which requires so
great a quantity of caloric to render it permanently elastic, as not
only keeps this sort of combustion under ignition, but much below the
degree of heat at which the accumulating vinous spirit could be raised
to the evaporable or distilling point, though capable, as already
observed, of detaching a considerable portion of it with the volatile
gas, and of the water of solution, or the water of composition recently
formed from the present attractions in its most volatile and incipient
state of formation; both which we have seen ascend with the fixed air
extricated, partly in a combined, and partly in an uncombined state.
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.