DISTILLATION.

The preparation of ardent spirits constitutes a manufactory which is carried on in this country to a considerable extent, and deserves a particular investigation, as connected with one of the most curious and intricate departments of chemistry. We shall treat the subject as briefly as is compatible with perspicuity and utility.

It seems established by the experiments of chemists, that no other substance can be converted into ardent spirits, by fermentation, than sugar. Different species of sugar have been recognized by chemists. They are distinguished from each other by their sweetening power, and by the figure of their crystals. As far as the process of distillation is concerned, it seems only necessary to refer to three of these species; namely, common sugar, sugar of grapes, or szigar of starch and manna.

Common sugar is usually extracted from the sugar cane, but it exists likewise in beet, and in various other vegetable substances. Its colour is white, and it crystallizes in rhomboidal prisms. When it is dissolved in a sufficient quantity of water, and mixed with yeast, it ferments, and the liquid thus fermented yields, when distilled, an ardent spirit. It is from the refuse of common sugar that the ardent spirit well known by the name of rum is' obtained in the West Indies.

Sugar of grapes is the substance to which that fruit is indebted for its sweet taste. It may be extracted from the juice of grapes, by nearly the same process as is followed by the manufacturers of common sugar. It is white, not so sweet as common sugar, and not so soluble in water. It usually crystallizes in spheres. These, when viewed with a glass, are found to consist of a congeries of small acicular crystals diverging from a centre. It is to the presence of this sugar that the juice of grapes owes its fermentability. The ardent spirits obtained by distilling wine are usually distinguished by the name of brandy. They are manufactured in great abundance in France and Spain, and other wine countries.

When starch is boiled with a large quantity of water and a little sulphuric acid for a considerable time, it is converted into a sugar, which possesses exactly the properties of sugar of grapes. From the experiments of M. Theodore de Saussure, it seems to follow that this sugar is nothing more than a combination of starch with water. During the process of malting, the starch which constitutes so great a portion of barley is converted into this sugar. If barley meal be mashed with water of the temperature 150°, and the mixture be well agitated for an hour or two, the barley starch gradually undergoes a process somewhat similar to mashing; for it becomes soluble in the water, and that liquid acquires a sweet taste. It is from this sugar that the ardent spirits known in this country by the names of Geneva, Wìiishy, Gin, are obtained.

Manna is a saccharine substance, which exudes spontaneously from the Fraxinus ora?«·, and several other species of ash. The fermented juice of the onion, melon, and carrot, likewise contains manna. Manna has a sweet taste like sugar. It is more soluble both in water and alcohol; it crystallizes very readily on cooling, in needles. But its most remarkable property is, that when dissolved in water, and mixed with yeast, it cannot be made to ferment like common or grape sugar. Hence it is incapable of yielding an ardent spirit. To the distiller, therefore, it is totally useless.

Milk likewise contains a peculiar species of saccharine matter, distinguished by the name of sugar of milk. In consequence of the presence of this substance, milk is capable of being fermented into an intoxicating liquor, which, ót’ course, if distilled, would yield an ardent spirit. This liquor is made by the Tartars, from the milk of mares, and is known by the name of koumiss. It is made likewise in Shetland.

The liquid which exudes from the cocoa-nut tree also contains a saccharine matter, but of what species has not been ascertained. In consequence of the presence of this saccharine matter, it runs readily into fermentation, and when the fermented liquor is distilled, it yields an ardent spirit, well known in India by the name of arrack.

Thus the name of the ardent spirits differs according to the material employed in its manufacture. Every species of ardent spirit is distinguished by a peculiar flavour. The opinion entertained at present is, that the nature of the . substance which produces intoxication is the same in all these ardent spirits, and is the substance to which chemists have given the name of alcohol ; and that the flavour is owing to the presence of an essential oil, derived from the ingredient employed in the manufacture. Thus the sugar cane yields the oil that gives the peculiar flavour to rum; grapes contain the oil that gives the peculiar flavour to brandy, and so on. We do not know that this opinion, though sufficiently probable in itself, has ever been established by decisive experiments; that the oils to which these spirits owe their flavour have ever been obtained in a separate state; or that all of these spirits have been made to yield alcohol destitute of flavour. But the opinion is so very likely to be true, that we will be forgiven for adopting it, especially as we are not aware of any counter evidence that can be brought forward.

The processes of the distiller being essentially the same, whatever the substance be from which he procures his ardent spirits, we shall satisfy ourselves with a minute account of the processes followed by the distillers in Scotland in manufacturing whisky. We shall introduce, likewise, a few observations on the processes followed in manufacturing ardent spirits in other countries, such as Hollands and Rum; and we shall terminate the article by giving the present state of our knowledge of the theory of fermentation.

CHAP. I. — OF THE MANUFACTURE OF WHISKY.

The kind of grain employed in this country for manufacturing whisky is barley. The processes are easier, and the spirits produced have a more agreeable flavour, when the barley is malted. But, in consequence of the duty upon malt, a portion of unmalted grain has been introduced into the distilleries. This portion has been gradually increased, and amounts very commonly to four fifths, and in some cases, it is said, to nine tenths, of the whole mixture of raw grain and malt. It may be laid down as a general rule, that the labour bestowed, and the time requisite for brewing, increases in proportion to the quantity of raw grain employed.

The processes of the distiller may be reckoned four: namely, the mashing, the cooling, the fermenting, and the distilling. We shall take each of these processes in the order in which we have named them.

1. The Mashing.

The barley is previously ground to a fine meal, and the malt bruised by passing it between rollers. When the [7:8:45]proportion of malt is very small, it is customary to add a quantity of the seeds of oats (the husk of oats separated during the grinding), to facilitate the separation of the water from the grains, after the process of mashing is over; for barley-meal parts with water with much greater difficulty than malt. When the proportion of raw grain to malt is as 2 to 1, or even as 3 to 1, this addition of oat seeds maybe dispensed with. But it is probably essential when the proportions amount to 5 to 1, or, still more, When to 9 to 1.

The quantity of grain and malt employed at one time must be entirely regulated by the size of the distillery. But, that we may be able to give a precise notion of the proportion of the different substances employed, we shall suppose the quantity taken at once to be 60 bushels, and that it consists of a mixture of two parts raw grain and one part malt, or,

40 bushels barley,

20 bushels malt.

The mash-tun is a large circular or square vessel, which now-a-days is usually constructed of cast iron. It was formerly of wood; but a wooden mash-tun was found to last for so short a time, that iron has been substituted in several distilleries with which we arc acquainted, and probably the substitution will soon become general. Into the mash-tun a quantity of water is let down of the temperature 150° Fahrenheit. The bulk of this water varies according to the fancy of the distiller; but from 700 to 800 wine gallons may be reckoned a good proportion for sixty bushels of grain. The mixture of mcal and bruised malt is then put into the mash-tun, and very carefully mixed with the water by a number of men, who wield each a wooden instrument adapted for the purpose. All the dry clots of mcal are broken, and every portion of it wetted with the water. This agitation of the meal in the water is what is technically called mashing. It is continued for at least an hour and a half, sometimes much longer; and the length of time must increase with the proportion of raw grain present, when compared with the malt; so that sometimes we have seen it continued for three or even four hours, z As the liquor in the mash-tun would lose a great deal of its heat during this length of time, about 500 wine gallons of water are added at intervals, at a temperature varying from 190° to 205°, according to the fancy of the brewer. After the mashing is concluded, the whole mixture is allowed to remain at rest for about two hours, and this interval is technically called the infusion. During this interval the grains sink to the bottom, and the ιcort, still muddy, but quite liquid, remains at the surface.

If we have the curiosity to taste the wort every half hour from the commencement of the mashing to the end of the process, we shall find that at first it has little taste, but that it becomes swccter and sweeter, till at last it acquires very nearly the luscious swcet taste of malt wort. This indicates clearly that the starch of the barley meal is gradually converted, during the mashing, into starch sugar. In what way this change is produced we have at present no experiments to determine; but if Theodore de Saussurc’s theory of the formation of starch sugar be accurate, we may conclude that the change is produced simply by the combination of a portion of water with the starch. The conversion, however, in the mash-tun, is never complete. A considerable portion of the starch still remains unaltered. The consequence is, that if we endeavour to make wort from raw grain, as strong as pos sible, to contain, for example, 200 lbs. of saccharine matter per barrel, we find ourselves unable to effect our object, because, long before it has reached 200 lbs. per barrel, the wort has lost its fluidity, and has assumed the form of a jelly. Our mode of trying this experiment was, to take the strongest raw grain wort which we could procure, and to concentrate it by boiling, till it became as strong as possible. We were never able, by this method, to obtain a wort much stronger than 150 lbs. per barrel. But malt wort may be easily boiled down to the strength of 200 lbs. per barrel, without losing its fluidity.

Probably the change of the starch into sugar continues during the process of fermentation. Hence, we conceive, the reason why distillers find it advantageous to put into the fermenting tuns all the solid starchy matter which had precipitated from the wort while in the coolers. Hence, also, the reason why the fermentation is conceived to go on best when it comes on gradually at first, and not with too much violence.

After the mashing and infusion is finished, the wort is drawn off from the grains. This is not done, as is the practice with the brewers, by opening a cock at the bottom of the mash-tun. It will not in this way pass through barley mcal. But it is drawn off from the top of the mash-tun, after the grains have subsided, by means of a tube pierced full of holes, which rises at one of the corners of the mash-tun as high as the surface of that vessel.

The quantity of wort that runs off in this way does not exceed one third of the water which had been mashed with the meal. If 1200 gallons of hot water, for example, have been employed in all, the wort drawn off after the mashing will scarcely exceed 400 gallons. If the process were carried no farther, almost two thirds of the wort would be lost. To prevent this, about 500 gallons of water, of the temperature 190°, are let upon the grains. The whole is well mixed together for about twenty minutes, and then allowed to infuse, or to remain at rest, for an hour and a half. It is then drawn off in the same way as the first wort. In general, the amount of the second wort is greater than of the first, because the grains having been previously deprived of a great proportion of their starch, now part with their water more freely than before.

To carry off everything soluble from the grains as completely as possible, after the second worts have been drawn off, about 800 gallons of boiling hot water are let on the grains. The mashing or stirring is continued for twenty minutes, and the infusion for half an hour or forty minutes. This third wort is then drawn off. Being much weaker than the two preceding worts, some distillers are in the habit of reserving it, and employing it for mixing with the meal and malt in the succeeding brewing. Others boil it down to the requisite strength, and then mix it with the first and second worts in the fermenting vessel. It is impossible to lay down any rule respecting this part of the process, because, unfortunately, the distiller is not left at liberty to follow his own judgment. The legislature has interfered, and obliged him to produce a determinate quantity of spirits of a given strength from 100 gallons of the fermented wort. Till within these few years it was necessary in Scotland to produce from 100 gallons of fermented wort, 19 gallons of spirits of the strength one to ten over hydrometer proof, or of the specific gravity 0∙90917. This law, we believe, still exists in England; but in Scotland the quantity of spirits from 100 gallons of fermented wort has been reduced to 14 gallons.^[1. Still more lately, an act of parliament has passed, reducing the product of spirits to thirteen gallons from the hundred gallons of wash, and the strength of the wort must not exceed 7θ lbs. of saccharine matter per barrel. The excise regulations bind down the distiller to a particular mode of operating. All such restrictions are very injurious to the improvement of the process. How far they may have been provoked by the attempts of the manufacturer to evade the excise duties, we pretend not to say. ] The Scotch distiller[7:8:46] at present is under the necessity of producing this quantity of spirits from 100 gallons of fermented wort, or, at any rate, of paying the duty for that quantity, whether he produce it or not. This law, of course, regulates the strength of his wort. For, in order to produce that quantity, it is necessary that the wort should contain a certain proportion of saccharine matter. Accordingly, the wort must be at least of the strength 55⅛ lbs. per barrel when it is let down into the fermenting tun, and the law prohibits it from being stronger than 75 lbs. per barrel. If we suppose the whole saccharine matter contained in the wort to be decomposed during the fermentation, 100 wine gallons would produce 14 gallons of spirits of the specific gravity 0∙90917, provided the original strength of the wort was 55^ lbs. per barrel. But this is a supposition which is never realized in practice. From a number of experiments, conducted with considerable care, we consider ourselves warranted in concluding, that, even when the fermentation is conducted with the greatest success, the quantity of saccharine matter which will remain undecomposed in a barrel of wort of the original strength of 55⅜ lbs. per barrel, cannot be less than 15 lbs. Hence a distiller can scarcely be expected to produce 14 gallons of spirits of the specific gravity 0∙90917 from 100 gallons of wort, unless the original strength of his wort was at least 70-∣ lbs. per barrel. In. general, indeed, a still greater strength than this will be requisite. Now, to produce wort of the strength 70∣ lbs. per barrel from raw grain, without boiling, is by no means an easy task. Formerly, when the product necessary was 19 gallons of spirits from the 100 of wort, the distillers were accustomed to give their wort the requisite strength by the process which they termed lobbing. This consisted in making up a very strong infusion of saccharine matter from malt, raw grain, &c. and adding it to the wort till it acquired the requisite strength. This substance was likewise called bub ; and every distiller had his own method of preparing it. Probably sugar, treacle, or other similar prohibited articles, often found their way into it. It was on this supposition that the addition of it to wort was entirely prohibited in the late act of parliament regarding the Scotch distilleries. And it was to prevent the secreting of the surplus spirits which might be produced above the 14 per cent, that the strength of the worts was limited to the maximum 75 lbs. per barrel.

When the quantities of grain, malt, and water, above indicated, are employed, the first worts drawn off will be about the strength of 73 lbs. per barrel, and the second worts of the strength 50 lbs. per barrel; and the two, when mixed together, would constitute a wort of the strength of about 62 lbs. per barrel. Of course, the worts actually made by the Scotch distillers must exceed the strength of those which we have employed by way of illustration, by about eight lbs. per barrel. But we have reason to believe that 62 lbs. per barrel would be a better strength than that pitched upon by those who contrived the act of parliament by which the Scotch distilleries are regulated. Wort of such strength should yield about 12 per cent, of spirits of the strength one to ten over proof, or of the specific gravity 0∙90917. The original strength of the wort from which Dutch Hollands is made is considerably less than this, and we believe that nobody will deny that the Dutch spirit is, in general, much preferable to the whisky manufactured in the lowlands of Scotland.

The whisky made by smugglers in Scotland is universally preferred by the inhabitants, and is purchased at a higher price, under the name of Highland whisky. This is partly owing to its being made entirely from malt; but the chief reason is, that, from the unfavourable circumstances under which they operate, their wort is necessarily much weaker than the wort of the legal distillers· Probably it is not much stronger at an average than the wort of the Dutch Hollands. It has been generally conceived that the superiority of the illicitly distilled, or Highland whisky as it is called, is owing to the mode of distillation. The smugglers distil in a much slower way than the legal distillers. But nothing can be more absurd than this opinion. The flavour of the spirits depends entirely upon the previous steps of the process. The slowness or rapidity of the distillation can make no difference whatever in the flavour, provided it be properly performed. Accordingly, we have seen spirits distilled by the very rapid mode of distillation that formerly was practised in Scotland, possessed of all the flavour of the best Highland whisky.

Great pains have been taken to put an end to the practice of illicit distillation in Scotland; and, by greatly diminishing the duty, this object, of late years, has been nearly attained. The smugglers formerly set the whole force of government at defiance, and carried on their processes in spite of all the attempts that were made to stop them. Many of them, indeed, were brought to absolute ruin, and few of them, we believe, were ever able to realize much money, or to rise to independence. But still a new race of smugglers rose up after another to carry on their illicit trade, to the great detriment of the revenue, and to an equal deterioration of the morals of the common people. Government do not seem to have been aware of the principal reason of the continuance of this evil. They bound down the legal distillers in such a manner by injurious restrictions, that it was not in their power to produce a spirit equal in flavour to that manufactured by the smugglers, who lie under none of those restrictions which bind down the ingenuity of the legal trader. This superiority induces a corresponding desire in the inhabitants of Scotland to possess themselves of smuggled whisky, even at a higher price than that for which they can purchase the same article from the licensed distillers. The smugglers, in consequence, are winked at, or rather encouraged, by a very considerable proportion of the inhabitants of the country. While this feeling existed it was impossible to put an end to smuggling in Scotland. But government of late has removed the restrictions by which the Scotch distillers were bound, so far as to allow them to distil from malt at nearly the same rate as they formerly did from raw grain. The consequence has been, that the high reputation of smuggled whisky has gradually sunk, and smuggling has been nearly discontinued.

The only reason that was alleged for continuing the restrictions under which the distillers were placed, was the allegation that they were necessary in order to ensure the payment of the duty upon the spirits actually distilled. But we conceive that this duty might be levied with as much accuracy, though all the restrictions on the strength of the wort were removed. From a number of experiments conducted upon a large scale, we conclude that the fermentation, however successful, is capable of decomposing only four fifths of the whole saccharine matter contained in the wort. Farther, we find, that for every pound of saccharine matter decomposed by the fermentation, there is formed half a pound of alcohol of the specific gravity 0∙825. Now every gallon of spirits of the specific gravity 0∙90917, or one to ten over proof, contains 4 - 6 lbs. of alcohol of the specific gravity 0∙825. To form a gallon of spirits, then, of the specific gravity 0∙90917, there is required the decomposition of 9∙2 lbs. of saccharine matter. But as only four fifths of the saccharine matter present are decomposed, we must increase 9∙2 by a fifth, which will raise it to 11⅛ lbs. The rule, therefore, for levying the duty on the distillers would be this. Ascertain, [7:8:47]by the saccharometer, the strength of the wort, or the number of pounds avoirdupois of saccharine matter which it contains, and for every 11∣ of these pounds charge the duty upon one gallon of spirits. This would be no hardship upon the distiller. If he is unable to produce a gallon of spirits from 11⅜lbs. of saccharine matter, he is not sufficiently acquainted with his business, and the necessity of paying the duty would stimulate his ingenuity to acquire the requisite information. He would soon discover two facts which would probably regulate his conduct; namely, that the flavour, and consequently the value, of his spirits, increases as he diminishes the strength of his wort, and that the produce of spirits from the same quantity of grain increases also as he diminishes the strength of his wort.

It would be difficult, according to the method at present followed by the distillers, for the excisemen to determine the strength of the worts with the requisite degree of accuracy; but it would be easy, we conceive, to order matters so, that this information might be gained without in the least injuring the process of fermentation to which these worts are to be subjected.

Some distillers, not satisfied with three mashes, which they think insufficient to exhaust the grains of all the matter that may be useful in the formation of spirits, add a fourth quantity of boiling water, after the worts of the third mash are drawn off, and mash a fourth time. The worts of this fourth mash are always kept, to be employed instead of pure water during next day’s brewing.

2. The Cooling.

Wort from raw grain has a much greater tendency to run into acidity than wort from malt. On that account the distillers endeavour to bring it down to the temperature requisite to begin fermentation as speedily as possible. As soon as the first worts have begun to run into the un-derback, they are made to pass into the coolers. The nature and disposition of the coolers vary so much, according to the size of the distillery, that a general description will by no means apply to them all. When the manufactory is of a moderate size, the coolers are a shallow wooden vessel, covering the floor of an apartment or suit of apartments, placed usually in the upper part of the distillery, and open as much as possible to the influence of the external air. Here the hot worts are pumped up, and left at a depth of one, two, or three inches, till they have acquired the requisite temperature.

When the distillery is on a large scale, it is usual to accelerate the cooling of the worts by agitation. Of late years a new contrivance has been fallen on, which answers much better than the old method, by bringing the worts almost instantly to the particular temperature which the distiller wishes them to acquire. This method is to pass the hot worts through a certain length of tin pipe, which is immersed in a running stream of water. By properly regulating the length of the pipe, the worts may be cooled down either to the temperature of the surrounding water, or to any other intermediate temperature required. As the worts in this case are cooled in close vessels, no evaporation goes on during the process. Hence their strength will not increase during the process, and the quantity will be precisely the same as in the underback, making allowance for the change of temperature. This probably would be a disadvantage to the distillers, while the present law obliges them to brew worts of a given strength. But if this restriction were removed, it would be rather an advantageous circumstance, because it would enable them to regulate the strength of their worts at pleasure, by the quantity of water employed during the mashing and infusion. To the excise officer it would also be a convenient circumstance, because it would afford an additional security for determining the strength with accuracy. He would have it in his power to try the strength of the worts while hot in the underback, and when newly let down into the fermenting tuns, before the yeast was added. This second trial ought to give nearly the same result as the first. We say nearly, because, when the worts are hot, it is not so easy to determine their strength with accuracy, as when they are cold.

During the cooling of the wort from raw grain, there is always a considerable deposit of flocky matter, which we conceive consists chiefly, if not entirely, of starch. This flocky matter is swept along with the wort into the fermenting tun. It is the opinion of distillers that it contributes materially to the formation of spirits during the fermentation. We have little doubt that the opinion is well founded. Probably during the fermentation it is converted first into saccharine matter, and then afterwards decomposed into alcohol and carbonic acid.

The temperature to which the wort is cooled before it is let down into the fermenting tuns differs a good deal in different distilleries, and even in the same distillery at different seasons of the year. Winter is the usual season for the distilleries, and it is the season which is considered as most advantageous for conducting the fermentation with success; for it is easy to raise the temperature of the fermenting room to the degree which is considered as best adapted for the precess. But when the weather is hotter than that degree, it is a much more difficult matter to keep the fermenting room sufficiently cool. In winter the distillers usually let down the first worts at about 70°; the second worts are cooled down to 60° or 65°. We do not perceive any good reason for this distinction, though we have frequently seen it practised.

3. The Fermentation.

This is by far the most important part of the whole process. It is by the skill and success with which it is conducted that distillers excel each other. Upon it the profit and loss of the manufactory chiefly turn. Much pains have been bestowed in investigating it; but it is of so capricious a nature as occasionally to thwart the most skilful and experienced brewers. We shall describe the method of proceeding in this process usually followed by the Scotch distillers. In the article Brewing we stated the facts at present known respecting the saccharine matter of the wort and yeast of beer which is employed as a ferment. To that article, therefore, we refer those who wish for information on these subjects.

The yeast employed by the Scottish distillers is chiefly brought from the London porter breweries. Small quantities may be occasionally obtained from breweries in their neighbourhood; but never, we believe, a sufficient quantity to answer their purposes. The best yeast is that which is thrown oft’ the top of the porter during its fermentation. But what is sold by the porter brewers consists chiefly of the slimy matter which remains at the bottom of the vessels when the clear porter is drawn off'. Fresh yeast is better than stale; but the distillers being unable to procure a sufficient quantity of fresh yeast for their purposes, are under the necessity of using both fresh and stale.

As the quantity of yeast employed depends upon its quality, it is therefore impossible to lay down any very precise rules upon the subject. For the quantity of wort which we have supposed in the preceding part of this article, a Scotch distiller would probably employ about twenty-seven gallons of good yeast, and about thirty-six gallons if he considered the yeast of inferior quality. Only a portion of this yeast is mixed at first with the wort. The [7:8:48]remainder is generally added on the second, third, and fourth day. Most commonly, indeed, the whole is added on the third day; but it is customary to make a farther addition at a later period, if the brewer is of opinion that the fermentation is not proceeding so well as it ought to do. We have seen yeast added on the sixth day of the fermentation.

The first portion of yeast mixed with the wort is always if possible fresh yeast, and it is a great object with the distiller to have it of as good a quality as possible. For our wort, the quantity of ycast first used may amount to nine gallons. On the second day nine gallons more may be added, and on the third day nine or eighteen gallons, according to its quality. Some distillers add nine gallons the first day, and twenty-seven the third. Some add nine gallons every day for four days. In short, there is considerable difference, and probably a good deal of caprice, in the practice followed in the various manufactories. At least we have never been able to obtain a satisfactory reason from any brewer why he followed one practice rather than another. In hot weather we should prefer the addition of nine gallons of yeast every day for four days. But in cold weather it would probably answer better to add the whole yeast at twice; and perhaps the third day is the most proper for making the great addition.

The fermentation lasts nine, ten, eleven, or twelve days, according to circumstances. Sometimes, though seldom, we have seen it last thirteen days. During the first five days the fermenting tuns are left open on the top, or only slightly covered; but pn the sixth day they are shut up as closely as possible, so as to render the escape of the carbonic acid rather difficult. Two reasons have been alleged for this proceeding. 1. The carbonic acid gas is conceived to carry with it a portion of the alcohol, and by binding down the top it is supposed that the loss by this drain will be diminished. We do not lay much stress on this reason. The fermentation is almost at an and before the tuns are shut down. Of course, almost the whole of the alcohol abstracted by the carbonic acid has been already removed. 2. The presence of carbonic acid is conceived to promote the fermentation. Hence it is supposed that, by preventing that gas from escaping with facility, the attenuation will be greater than it otherwise would be. Perhaps there may be some foundation for this opinion. There is no doubt that carbonic acid gas may be substituted for yeast as a ferment, and that the fermentation of the wort, under such circumstances, will go on pretty well. We have seen the experiment tried by mixing yeast with wort in a close barrel, from which there proceeded a tin pipe that passed through another barrel filled with wort, and opened at the bottom of it. The gas was absorbed by the wort in this second barrel, and the wort was fermented by it. But the fermentation, as might have been expected, was not so complete as if it had been produced by the usual addition of yeast. The distillers do not collect any yeast from their fermenting vats, but beat it all into the liquid, being of opinion that any such collection would render the fermentation less complete, and, of course, diminish the proportion of spirits obtained.

The wort most commonly increases in temperature from 20° to 25° of the thermometer. Supposing it let down into the fermenting tun at 57°, its temperature, when at the highest, may amount to from 78° to 82°. It usually acquires the highest temperature on the fourth day of the fermentation, frequently upon the fifth day; sometimes upon the sixth, the third, or the seventh day; and we have seen it as late as the eighth, or even the eleventh day, before its temperature became a maximum.

The following table exhibits the number of cases on which the highest temperature took place in these respee tive days in seventy-six brewings, conducted upon a pretty large scale:
[table]

This diversity, no doubt, depends upon the goodness of the yeast employed; and, as we have no good criterion by which to determine the exact value of yeast as a ferment, it is impossible to be able to foretell the exact result in any particular case. Indeed we consider the uncertainty of the value of ycast as the great difficulty which the distiller has to encounter. Any person who could discover a method of estimating the exact value of any particular yeast as a ferment would greatly improve this difficult manufactory. We do not believe that such a discovery is impossible. Perhaps the specific gravity of the yeast, or the quantity of solid matter which is left behind when a given weight of the yeast is evaporated to dryness, might furnish very material information. We are rather surprised that no distiller has thought of subjecting yeast to a series of experiments, with a view to ascertain its real value as a ferment. The new information which he would acquire would more tlían compensate for the trouble, and would probably give him the means of improving his manufactory, or at least of forming some notion of the value of the yeast which he purchases.

As the fermentation proceeds, the specific gravity of the wort diminishes, owing to the decomposition of the saccharine matter, and its conversion into alcohol and carbonic acid. This diminution of specific gravity is called attenuation by distillers, and is employed by them as the measure of the success of the fermentation. They can easily foretell the quantity of spirits which their τvash (the name by which their fermented wort is distinguished) will yield, if they know the attenuation which has taken place during the fermentation. This diminution of specific gravity is produced by two causes. 1.The destruction of the saccharine matter previously dissolved in the liquid, and which occasioned its specific gravity to be greater than that of water. If the whole of this saccharine matter were decomposed, it is obvious that the change of specific gravity from this cause would be exactly such as would sink the wash to the specific gravity of water. 2. The second cause of the diminished specific gravity of the fermented wort is the formation of a quantity of alcohol, which, being lighter than water, occasions, by its evolution, a corresponding diminution of the specific gravity of the liquid. The specific gravity of the purest alcohol which it has been hitherto possible to obtain, is 0∙793 at the temperature of 60°. When mixed with water it enters into a chemical combination with that liquid. Hence the specific gravity is greater than the mean of that of the water and alcohol, though considerably less than that of water. It is obvious, if we were to add alcohol to the unfermented wort, we would diminish its specific gravity. We might even, by this means, render it as light, or even lighter, than water, though none of the saccharine matter were destroyed. It is obviously impossible, therefore, to determine how much saccharine matter has been decomposed by the fermentation from the attenuation alone. Suppose the original specific gravity of the wort to have been 1'060; and suppose that, after the fermentation, its specific gravity is reduced to 1∙002. The first of these specific gravities indicates 55∙8 lbs. of saccharine matter per barrel; the second 1∙6 lbs. per barrel. It does not follow, as the distillers suppose, that 54∙2 lbs. of saccharine mat-
[7:8:49]
[table]

ter per barrel have bccn decomposed and converted into alcohol and carbonic acid. A considerable portion of the saccharine matter still remains undecomposed, but the alcohol which has been formed counteracts the specific gravity of this saccharine matter, and prevents its presence from being correctly indicated by the saccharometer. But if we measure out a quantity of such wash, put it into a retort or still, and distil off about a third of it; if we then take the residual wash which remains in the retort or still, and add pure water to it till its original bulk be restored, the saccharometer being applied to it will indicate the quantity of saccharine matter which it still contains; and this quantity being subtracted from the original quantity of saccharine matter contained in the wort before the fermentation commenced, the remainder will be the saccharine matter decomposed by the process.

Alcohol is a substance which has a tendency to stop fermentation, and it stops that process completely when added to fermenting wort in sufficient quantity. It must be obvious from this, that very strong worts are injurious to the profits of the distiller; because the stronger the wort the greater will be the proportion of alcohol evolved, and, of course, the fermentation will ultimately be impeded or stopped altogether, before the whole saccharine matter is decomposed. Accordingly, the spent wash will always be found to contain a considerable proportion of saccharine matter, and it might be fermented again, and made to yield no inconsiderable quantity of spirit. The writer of this article made nine trials with malt worts, which were designedly made weak. They were fermented as thoroughly us possible, and the following table indicates the specific gravities to which they were reduced. The original specific gravity probably did not much exceed 1∙045.

Upon examining the state of the wash after the fermentation was at an cud, we found that 4'34 parts of the sac 7 charine matter had been decomposed, and that one part remained unaltered. So that in these nine experiments, which were as favourable as possible to the fermentation, on account of the weakness of the worts, not much less than one fifth of the whole saccharine matter remained unaltered. Surely then we may lay it down as a fact, that, in all cases of fermentation in a Scotch distillery, at least one fifth of the whole saccharine matter is prevented from being decomposed by the antifermenting power of the alcohol evolved. The consideration of this circumstance renders it of more importance to allow the distiller to make his wort weak; for the weaker the original wort, the less will the quantity be of the saccharine matter which is prevented from being decomposed by the presence of the alcohol evolved.

When the heat has acquired its maximum, we may reckon, at an average, that nine tenths of the whole attenuation has been completed. No judgment can be formed of the ultimate attenuation, by the rapidity or slowness with which the heat reaches its maximum. We have seen the attenuation equally good when the maximum temperature happened on the third, fourth, fifth, or sixth day.

It is impossible to lay down any specific rule with respect to the length that attenuation ought to be carried. The obiect of the distiller is to render his wash, if possible at least, as light as water. This object they frequently accomplish. But it sometimes happens that the fermentation stops when the specific gravity has sunk to 1 ’ 013 or 1∙008, and no addition of yeast will make it sink lower. Bad yeast is the most probable reason of this ill success. If the wash be allowed to remain in the fermenting tuns after the fermentation is at an end, its specific gravity will be found gradually to increase a little, and it will not yield so great a proportion of spirits. This is owing to the formation of vinegar in the wash, which takes place at the expense of the alcohol; and if the vinegar-forming process were allowed to go on long enough, the alcohol would disappear altogether.

Distillers always ferment their worts in tuns of a large size. This is attended with the advantage, that the artificial heat evolved by the fermentation is not so speedily dissipated as it would be if the process were conducted in small vessels. Some distillers fill the tuns only partly', leaving a portion of the upper part empty, that it may contain the froth formed when the wort is in full fermentation. Others fill the tuns almost to the top, and cover down the mouth with a lid, from which a tube passes to an open vessel placed above the tun. When the liquid swells by the fermentation, it passes up the tube into the open vessel, and runs down again when the fermenting process subsides. No regular set of experiments, that we know of, has been made to determine which of these two methods is the best. ·

We have already observed that every 9∙2 lbs. of saccharine matter really decomposed by the fermenting process yield a gallon of spirits one to ten over hydrometer proof, or of the specific gravity 0∙90917 (at the temperature of 60°). But as the distillers are not in possession of a good method of determining how much saccharine matter has been decomposed, the easiest rule will be to allow 1I∣lbs. of saccharine matter, estimated before the fermentation begins, to yield a gallon of spirits at 0∙90917 specific gravity. If the original worts be very weak, perhaps we might take 11 lbs. of saccharine matter as producing that quantity' of spirits; but while the present law respecting the strength of the worts continues, 1l⅛ lbs. will be found, upon an average, to come very' near the truth.

It does not seem to be possible to ferment wort from a mixture of raw grain and malt as completely as is required for the purposes of the distiller, without its becoming sour. There seems no reason to doubt that the acid formed is the acetic. Some are of opinion that the presence of this acid contributes to improve the flavour of the spirits. But the quantity of acetic acid usually present in wash is so small, that we do not see any reason for supposing that it can produce any sensible effect. It is important, therefore, that the acidity should be as small as possible, because the acid is formed at the expense of the alcohol in the wash. Hence the wash ought to be distilled as soon as the fermentation has come to a conclusion.

4. The Distilling.

The stills commonly used in other countries are of large dimension, and very deep, so that a great deal of time is necessary to finish one process. Once in the week, for example, is no uncommon period. The same kind of still was used in Scotland till about the year 1787, when the duty began to be levied on the distillers by a license paid at the commencement of the season upon every still according to its capacity. This was done to prevent that propensity to smuggling by which the generality of Scotch distillers were supposed to be actuated. The quantity of spirits which a still of given dimensions could produce in a year was calculated, and the license was laid on according to it. This saved the excise-officers all farther trouble, [7:8:50]after gauging the stills and collecting the license-duty, excepting an occasional visit to be certain that no new still of larger dimensions was substituted for the old one. But about the year 1788 Messrs John and William Sligo, at that time rectifiers in Leith, made an important alteration in the shape of the still, at the suggestion of an Englishman, which greatly increased the rapidity of distillation. They diminished their height, and increased the diameter of their bottom. The consequence of this alteration was, that they were able to distil off the contents of the still in a few hours, instead of once a week, as had formerly been the practice. Thus they were enabled to produce a great quantity of spirits from a very small still, and, of course, paid in reality a much smaller duty than their brother manufacturers. This lucrative improvement they possessed exclusively for about a year; but a secret of such importance could not be long confined to a single house. It became gradually' known to other distillers, and was soon imitated by all. The license-duty was increased year after year; but the ingenuity of the distillers enabled them to outstrip the acts of parliament; till, at last, a committee of the House of Commons was appointed to investigate the subject in 1799. A very bulky report was published by this committee, which contains a vast collection of curious facts respecting the. mode of distillation at that time practised in Scotland. The license, in consequence of this report, was laid on the distiller, on the supposition that he could discharge his still every eight minutes, during the whole season that the manufactory was in activity. Since that time the time of discharging the still was considerably shortened. But the saving in point of time was attended with such an enormous waste of fuel, that it is rather doubtful whether it was attended with much additional profit to the distiller. In the year 1815, which was the last year of the license-duty, a still capable of holding 80 gallons could be completely distilled off, emptied, and ready for a new operation in 3∣ minutes, or even, it is said, in some cases in 3 minutes; and a still of 40 gallons in 2∣ minutes. At that time a change took place in the excise laws; the license-duty was abolished, and the whole duty was levied, as in England, on the wash and the spirits produced. There was, of course, no longer any necessity for continuing the rapid mode of distillation; and, as it was attended with a very considerable waste of fuel, and was in other respects much more expensive than the slow process, it has been, of course, discontinued. We conceive, however, that it will be worth while to give a short description of the still and furnace which the Scotch distillers employed during the existence of the license-duty. It would be a great pity indeed to allow the results of such a series of important experiments to be forgotten.

The stills were made of copper. Those capable of holding 44 gallons were about 44 inches in diameter at the bottom, and about 5 inches deep. Those capable of holding 80 gallons were 54 inches in diameter, and about 8 inches deep. The bottom was perfectly flat, and about three eighths of an inch thick. Within it there were a number of iron chains, which were turned round by machinery, and rubbing against the bottom prevented the thick matter, which the wash always contains, from adhering to the bottom of the still and catching fire. This would have almost immediately occasioned the destruction of the still; and the scorched starchy matter would have communicated a disagreeable flavour to the spirits, which could not have been got rid of afterwards. There was likewise a circular plate in the inside of the still, towards its top. The use of it was to break the bubbles that rise during rapid distillation; and, of course, lessen the risk of the still boiling over, or running foul as the distillers term it; and, consequently, the distiller was enabled to put a greater charge of wash into the still than it would have been in his power to do if the plate had been omitted.

These stills were supported by resting an inch and a half on the brick work all round the bulge. The furnace was quite level, and was placed at the distance of 15 inches below the bottom of the still. The inner end of the grating bars was placed 15 inches within a line falling vertically from the part of support of the bulge of the still. The bars were in two lengths, the inner length was 21 inches, the outer 30 inches, supported by a cross bar between them four inches square. In front of the bars was a dumb plate 10 inches broad. The bottom of the ashpit was three feet below the grating bars, and on a level with the floor of the distillery. The bars were two inches thick, three inches deep, and three fourths of an inch apart. The brick work extended 21 inches beyond the dumb-plate, and was four feet wide and four inches higher outside than at the bulge of the still. The furnace doors were 30 inches wide. The bottom of the furnace beyond the grating bars was lined with fire-brick nine inches deep, and passed level backward into the chimney.

The chimney was 60 feet high, four feet square within from top to bottom, and consisted of a double wall. The inner wall of fire-bricks was nine inches thick. The outer wall was placed at three inches distance on all sides from the inner wall, and the space was left open at the top. The outer wall was 18 inches thick at bottom, diminishing regularly on the outside till reduced to nine inches at top. The two walls were tied together, at certain distances, by long fire-bricks. This separation of the two walls was found to prevent the rapid destruction of the chimney from the intensity of the fire, which always happened when the two walls were in contact.

Such was the construction of the furnace and the shape of the stills during the time that rapid distillation was practised in Scotland, when both had been brought to the greatest degree of perfection which the distillers were capable of giving them. The writer of this article has not had an opportunity of seeing the shape of the stills used by the Scotch distillers since the license-duty was abolished. But it is probable that the old shape will not have been entirely restored; but that the present stills, though much larger in size, imitate the late stills in the great diameter of their bottom, and their comparative shortness when compared with the stills employed by the English distillers.

The top of the still ends in a kind of tube, which is bent downwards, and connected with a tin tube, which makes a number of revolutions in a large vessel filled with cold water, and therefore called the worm. This large vessel is called the refrigeratory, and care is taken to keep the water in it always cool by means of a stream of water which is constantly flowing into it. The wash being put into the still, and the top being fixed down, heat is applied to the vessel till it is made to boil. The spirits being more volatile than the water, pass over first in the state of steam, and are condensed into a liquid as they pass through the worm. The first portions that come over are very strong; but the strength diminishes as the process proceeds. The distiller continues the distillation till the liquid which flows front the worm is as heavy as water, or at least so nearly so that the quantity of spirits remaining is not considered as a compensation for continuing the process any longer. The strength of the liquid proceeding from the worm is ascertained by a small hydrometer, with which it is tried every now and then; and whenever a certain mark on the instrument comes to coincide with the surface of the liquid, a cock at the bottom of the still is opened, and what remains in the still is let off. This liquor is called the spent wash. It is a muddy brown liquid, still containing a quantity of undecomposed saccharine[7:8:51] matter. It is therefore used as food for cattle. These animals are fond of it, and soon fatten upon it.

To prevent the still from boiling over, which is apt to happen towards the commencement of the distillation, it is usual to throw a piece of soap into the vessel along with the wash. This substance is partly decomposed, and the oily matter which it contains spreading on the surface, forms a thin coat, which breaks the large bubbles when they reach it, and thus prevents the wash from swelling beyond the requisite bulk. Butter would answer equally well with soap, and would he less apt to give a disagreeable flavour to the spirits; but its high price prevents the possibility of using it for that purpose. We have some suspicion that hogs’ lard would answer. If it were found to do so, it would be cheaper than soap, and less apt to give a bad flavour to the spirits. The supposition, however, that soap communicates a disagreeable flavour to spirits, though very generally entertained, is, we believe, a mistake. We have certainly met with spirits distinctly tainted with soap, and having in consequence a highly nauseous taste. But this was at a time when the rapid mode of distilling was only on its progress to perfection, and was owing, we believe, to little bits of the soap having been accidentally forced into the worm, and afterwards dissolved by the spirits.

It is impossible to lay down any rule with respect to the strength of the weak spirit obtained by this first distillation, and which is called low wines in Scotland. That strength must depend partly upon the original strength of the wort, partly on the attenuation which has taken place during the fermentation, but chiefly upon the attention of the distiller to distil off the whole of the spirituous portion of the wash. In a great number of cases in which we have had the curiosity to determine the strength of the low wincs in distilleries, we have found the specific gravity at 60°, differing but little from 0'978; frequently a little weaker, and very rarely a little stronger. Low wines of this strength contain the fifth part of their weight of alcohol of the specific gravity 0 ’ 825; the remaining four fifths are water.

The low vyines are put into the still and subjected to a second distillation, which in Scotland is called doubling. The first portion which comes over is a milky liquid, known by the name of foreshot. Its taste is disagreeable, and on that account it is received by itself, and returned back into the low wines to be subjected to another distillation. The properties∙of the foreshot are owing to an oil with which it is loaded. When the spirits begin to run transparent from the end of the worm, they are allowed to run into a receiver prepared for them. Whenever their specific gravity, determined by the hydrometer, has reached a certain point, they are no longer allowed to flow into the receiver containing the spirits, but into a place by themselves, and the distillation is continued till the liquid coming over has approached very nearly to the specific gravity of water. This third portion is called faints. It is mixed with the low wines and distilled again. Thus the distillation of the low wines is continued till the whole of their alcoholic part is brought to that degree of strength which fits them for the market. The strength at which the duty is levied on -them is one to ten above hydrometer proof, which corresponds with the specific gravity 0 ’ 90917. They are prohibited from sending out of their manufactory spirits of greater strength than this, or of a strength under one in six below proof, or of the specific gravity 0'9385. Between these two intervals the specific gravity of their spirits may be considered as vibrating; for it is not to be expected that they should be able always to produce spirits of exactly the same specific gravity. We have found the spirits, as obtained by doubling, of a specific gravity as low as 0∙908, and as high as 0∙925. No doubt they might be obtained much stronger or much weaker than these two extremes, if there were any object in view to induce the distiller to alter his usual practice.

Such is the mode followed in Scotland in order to obtain whisky. The distillers are at pains to purchase the best English barley which they can procure. They are certainly in the right to select English barley for malting; for English barley, when malted, yields more spirits than in the state of raw grain. But for that portion of grain which they use in the distilleries without malting, it would be their interest to employ the best big which they can procure; for good big, while in the state of raw grain, yields rather more spirits than an equal quantity of the best English barley; and as it can be purchased at a cheaper rate than barley, it could obviously be employed with economy as a substitute for that grain. Big is greatly deteriorated by malting it; of course it would be improper to employ it in distilleries in that way; but the distillers might employ it in the state of raw grain with great advantage.

CIIAP. II. — OF THE MODE OF MANUFACTURING OTHER KINDS OF SPIRITS.

In this chapter we shall merely make a few very short observations on the processes followed by the distillers in other countries.

1. Dutch Geneva.

The Dutch have long been famous for the manufacture of an excellent kind of spirits, known in Scotland by the name of Gin, in England by the name of Hollands, and sometimes by the name of Geneva. W r e have been told that the manufacture of it originated in the city of Geneva, and that this was the origin of the name Geneva, still applied to it in commerce; but we have no means of determining how far this statement may be depended on. We have not seen in print any accurate account of the mode of making Geneva practised by the Dutch; but the following account may, we believe, be relied on. We are indebted for it to a friend, who about forty years ago went over to Holland on purpose to make himself acquainted with the process. His object was to establish a similar manufactory in Scotland. But the severe laws by which the Scotch distillers were soon after bound put it out of his power to execute his plan.

112 lbs. of barley malt, and 228 lbs. of rye-meal, are mashed together with 460 gallons of water of the temperature 162°. After the infusion has stood a sufficient time, cold water is added till the strength of the wort is reduced to 45 lbs. per barrel. The whole is then put into a fermenting back, at the temperature of 80°. ∙ The vessel is capable of holding about 500 gallons. Half a gallon of yeast is added. The temperature rises to 90°, and the fermentation is over in forty-eight hours. The attenuation is such that the strength of the wash is not reduced lower than 12 or 15 lbs. per barrel. The wash is put into the still with the, grains and all. The low wines, as usual, are distilled again, and the spirits of the second distillation are rectified; so that the Hollands pass thrice through the still. A few juniper berries and some hops are used to communicate a peculiar flavour to the spirits.

, Now, 45 lbs. per barrel constitute a wort so weak that it will not yield above seven and a half per cent, of spirits of the usual strength; so that the produce which the Dutch obtain from their wort cannot amount to much more than half what the Scotch distillers are obliged to produce from theirs.

It is obvious, from the preceding account, that the fermentation[7:8:52] is very imperfectly accomplished in the Dutch process. The small quantity of yeast employed, and the short time that the wort is allowed to ferment, necessarily imply imperfection in the fermentation. And this is obviously the case, for the original strength of 45 lbs. per barrel is only reduced to 15 lbs. per barrel. We have often seen the attenuation of the porter-in the London breweries not much less complete. What advantage is gained by putting the grains into the still along with the wash we have not the means of determining. Such a practice can only be followed in distilleries upon a very small scale. W*e do not see how it could be practised in the Scotch distilleries. Indeed, we have no doubt whatever, that when the mashing is repeated a sufficient number of times, and the grains sufficiently washed with hot water, every thing likely to contribute to the formation of spirits will be carried off.

Every person acquainted with the flavour of Hollands and Ļowland whisky, must admit that the former is greatly superior to the latter. Indeed the flavour of Hollands is equal to that of malt whisky. This is owing in part to the small proportion of raw grain used by the Dutch distillers. 112 lbs. of barley malt may be reckoned at three bushels. We do not know the average weight of a bushel of rye; but if we suppose it to be 50 lbs. 228 lbs. will amount to about 4∙∣ bushels; so that, in the Dutch distilleries, the malt bears to the raw grain the proportion of two to three. We suspect that another reason of the superiority of the Dutch spirit over the Scotch, is the small quantity of ycast employed by the manufacturers of Hollands. The vast quantity of porter yeast used by the Scotch distillers, often in a state almost approaching to putrefaction, cannot but have an injurious effect upon the flavour of their spirits, and has undoubtedly contributed to the superior reputation of Highland over Lowland whisky; for the Highland distillers (especially the smugglers) have not the means of procuring yeast from London. Of course their wash is less perfectly fermented, but the flavour of their spirits is much more agreeable. We think, indeed, that the flavour communicated by the yeast to Scotch Lowland whisky may be distinctly perceived, and on that account are disposed to suspect that the flavour of the spirits always suffers in proportion as the fermentation is brought nearer a state of perfection. Any person who should find out a method of fermenting wort without the necessity of employing such quantities of porter yeast as the distillers use, would undoubtedly prodigiously improve the flavour of the spirits manufactured by the Scotch distillers. If government were to make such an alteration in the laws as would enable the distiller to employ a greater proportion of malt without any material increase of expense, the object might be considered as accomplished. In the present state of the manufactures of Great Britain, it would be impossible to confer a greater favour on the country than a thorough revisal of the excise laws, under the auspices of a set of individuals at once intimately acquainted with the most improved state of chemical science, and with the most liberal principles of political economy. Every thing that improves the quality and diminishes the price of our manufactures is of more value to the country than our legislators seem to be aware of.

We do not think that Hollands could be manufactured in Great Britain with any probability of success. The experiment was tried at Maidstone, in Kent, by a Mr Bishop, who had interest enough with Mr Pitt to get a special clause introduced into an act of parliament permitting him to manufacture Hollands according to the Dutch method; but the manufactory was never successful. The Maidstone Hollands never acquired much reputation. The distillery languished for some years, and then terminated in a bankruptcy. Some attempts have been lately made to revive the Maidstone establishment; but we may venture to predict that they will not be successful.

2. Plum.

This is the name given to a spirit manufactured in the West India islands, from the molasses, &c. which remain after the sugar is separated in small crystals from the boiled juice of the sugar cane. We do not know any thing about the origin of the word rum, or the time at which the manufacture of this spirit commenced; not, probably, till after the West Indies were colonized by Europeans. At present it is chiefly in the islands belonging to Great Britain that this spirit is made. The process, as we obtained it from a Dominica planter, who had for many years been in the habit of making this spirit, is as follows:

Twelve parts of sweets are dissolved in 100 parts of water, and fermented as completely as possible by means of yeast, which is chiefly obtained in the distillery itself by means of the fermentation of the rum wort, which gradually generates it. Fourteen gallons of spirits, one to ten over proof, are obtained from 100 gallons of wash. If this statement be correct, the produce of spirit from molasses exceeds considerably what can be obtained in this country from barley. A solution of 12 parts of sugar in 100 of water would make a wort containing about 44 lbs. of saccharine matter per barrel; from 10Ó gallons of which, in this country, we would not obtain more than 8 gallons of spirits of the above strength; but we suspect some mistake on the part of our informer, as he communicated the process to us in this country several years after he had given over the actual superintendence of his rum distillery.

The peculiar flavour which distinguishes rum, and makes it so agreeable to the taste, is undoubtedly owing to a peculiar oil contained in the sugar-cane; for when spirits are made in this country from sugar, they are entirely destitute of the peculiar flavour of rum, and resemble, in their properties, the common spirit made in this country from barley. The colour of rum is derived from the oak casks in which it comes to this country from the islands in which it is made.

CHAP. III. — ON THE NATURE OF THE VINOUS FERMENTATION.

In the article Brewing we have given a short sketch of the facts hitherto ascertained respecting the nature of the change which saccharine matter undergoes when fermented; and we have very little to add to the facts stated in that article. We shall merely enter a little more minutely into the detail of facts than we thought necessary under the article Brewing.

Common sugar has been analysed by Gay-Lussac and Thenard, by Berzelius, and by Dr Prout. The method followed by each differed a little from that of the others, and the results, though they do not quite tally, certainly approach considerably to each other. The following table exhibits the composition of 100 parts of sugar, according to each of these chemists:
[table]

To be able to determine from these analyses the number of atoms of oxygen, carbon, and hydrogen, which are [7:8:53]requisite to form a constituent particle of sugar, it would he requisite, in the first place, to be able to specify the weight of sugar capahle of neutralizing a given weight of any solifiable base. Berzelius found, that when a solution of a given weight of sugar in water was digested over oxide of lead, the oxide was at first dissolved; but, after a certain interval of time, a light white powder makes its appearance. This powdcr is a compound of sugar and oxide of lead, and is composed, according to Berzelius’s analysis, of
[table]

Now the equivalent number for oxide of lead is 14. It follows from this, that if the white powder be a compound of an atom of sugar and an atom of oxide of lead, the weight of an atom of sugar is 10. But we have no evidence whatever for adopting one atom of sugar in this compound rather than two. And as one atom will not accord with the phenomena of fermentation, it is better to consider the white powder as a compound of one atom oxide of lead and two atoms of sugar. On that supposition an atom of sugar will weigh about five. Now, if we suppose it to be composed of
[table]

the weight of an atom of sugar will be 5∙625, which does not differ very much from the weight, as resulting from Berzelius’s analysis; not more, indeed, than might be expected from the extreme difficulty of analysing such a compound with precision. But if we suppose the weight of an atom of sugar to be as now stated, 100 parts of it will be composed of
[table]

Now, as these numbers are almost exactly the same with those of Dr Prout, we are disposed to consider them as representing the true constituents of sugar.

From the phenomena of fermentation, as described under the present article, and in the article Brewing, it appears that by the fermentation the sugar is decomposed and converted into alcohol and carbonic acid. Alcohol, according to the analysis of Theodore de Saussure, is composed of three atoms hydrogen, two atoms carbon, and one atom oxygen. Carbonic acid is composed of two atoms oxygen and one atom carbon. Hence the weight of an integrant particle of alcohol is 2∙875. For
[table]

And an integrant particle of carbonic acid weighs 2*75.

We see likewise that a particle of sugar is capable of being decomposed into an integrant particle of alcohol and an integrant particle of carbonic acid. For a particle of alcohol is composed of
[table]

both together, we see, corresponding to the number of atoms in a particle of sugar.

If fermentation then be merely the separation of sugar into an atom of alcohol and an atom of carbonic acid, there ought to be formed,
[table]

But alcohol of 0∙825 contains about the fifth of its weight of water. Hence by fermentation sugar is converted into
[table]

Now these proportions approach very nearly the results obtained by Lavoisier and Thenard. We are disposed therefore to consider the explanation which we have given as likely to be the true one.

In what way the yeast acts, if no portion of it enter into the composition of the alcohol or carbonic acid, as would appear from what we know of the subject, we have no means at present of forming a conception. It would be requisite, before we could reason on the subject, to be better acquainted with the composition of yeast than we are at present. (l.)