Conversations on Chemistry Part 92

Like barley and most other seeds, it is insipid until it has undergone the saccharine fermentation; and this, you must recollect, is always a previous step to the vinous fermentation in those vegetables in which sugar is not already formed. Brandy may in the same manner be obtained from malt.

CAROLINE.

You mean from beer, I suppose; for the malt must have previously undergone the vinous fermentation.

MRS. B.

Beer is not precisely the product of the vinous fermentation of malt.

For hops are a necessary ingredient for the formation of that liquor; whilst brandy is distilled from pure fermented malt. But brandy might, no doubt, be distilled from beer as well as from any other liquor that has undergone the vinous fermentation; for since the basis of brandy is alcohol, it may be obtained from any liquid that contains that spirituous substance.

EMILY.

And pray, from what vegetable is the favourite spirit of the lower orders of people, gin, extracted?

MRS. B.

The spirit (which is the same in all fermented liquors) may be obtained from any kind of grain; but the peculiar flavour which distinguishes gin is that of juniper berries, which are distilled together with the grain--

I think the brandy contained in the wine which we are distilling must, by this time, be all come over. Yes--taste the liquid that is now dropping from the alembic--

CAROLINE.

It is perfectly insipid, like water.

MRS. B.

It is water, which, as I was telling you, is the second product of wine, and comes over after all the spirit, which is the lightest part, is distilled. --The tartar and extractive colouring matter we shall find in a solid form at the bottom of the alembic.

EMILY.

They look very like the lees of wine.

MRS. B.

And in many respects they are of a similar nature; for lees of wine consist chiefly of tartrit of potash; a salt which exists in the juice of the grape, and in many other vegetables, and is developed only by the vinous fermentation. During this operation it is precipitated, and deposits itself on the internal surface of the cask in which the wine is contained. It is much used in medicine, and in various arts, particularly dying, under the name of _cream of tartar_, and it is from this salt that the tartarous acid is obtained.

CAROLINE.

But the medicinal cream of tartar is in appearance quite different from these dark-coloured dregs; it is perfectly colourless.

MRS. B.

Because it consists of the pure salts only, in its crystallised form; whilst in the instance before us it is mixed with the deep-coloured extractive matter, and other foreign ingredients.

EMILY.

Pray cannot we now obtain pure alcohol from the brandy which we have distilled?

MRS. B.

We might; but the process would be tedious: for in order to obtain alcohol perfectly free from water, it is necessary to distil, or, as the distillers call it, _rectify_ it several times. You must therefore allow me to produce a bottle of alcohol that has been thus purified. This is a very important ingredient, which has many striking properties, besides its forming the basis of all spirituous liquors.

EMILY.

It is alcohol, I suppose, that produces intoxication?

MRS. B.

Certainly; but the stimulus and momentary energy it gives to the system, and the intoxication it occasions when taken in excess, are circ.u.mstances not yet accounted for.

CAROLINE.

I thought that it produced these effects by increasing the rapidity of the circulation of the blood; for drinking wine or spirits, I have heard, always quickens the pulse.

MRS. B.

No doubt; the spirit, by stimulating the nerves, increases the action of the muscles; and the heart, which is one of the strongest muscular organs, beats with augmented vigour, and propels the blood with accelerated quickness. After such a strong excitation the frame naturally suffers a proportional degree of depression, so that a state of debility and languor is the invariable consequence of intoxication.

But though these circ.u.mstances are well ascertained, they are far from explaining why alcohol should produce such effects.

EMILY.

Liqueurs are the only kind of spirits which I think pleasant. Pray of what do they consist?

MRS. B.

They are composed of alcohol, sweetened with syrup, and flavoured with volatile oil.

The different kinds of odoriferous spirituous waters are likewise solutions of volatile oil in alcohol, as lavender water, eau de Cologne, &c.

The chemical properties of alcohol are important and numerous. It is one of the most powerful chemical agents, and is particularly useful in dissolving a variety of substances, which are soluble neither by water nor heat.

EMILY.

We have seen it dissolve copal and mastic to form varnishes; and these resins are certainly not soluble in water, since water precipitates them from their solution in alcohol.

MRS. B.

I am happy to find that you recollect these circ.u.mstances so well. The same experiment affords also an instance of another property of alcohol,--its tendency to unite with water; for the resin is precipitated in consequence of losing the alcohol, which abandons it from its preference for water. It is attended also, as you may recollect, with the same peculiar circ.u.mstance of a disengagement of heat and consequent diminution of bulk, which we have supposed to be produced by a mechanical penetration of particles by which latent heat is forced out.

Alcohol unites thus readily not only with resins and with water, but with oils and balsams; these compounds form the extensive cla.s.s of elixirs, tinctures, quintessences, &c.

EMILY.

I suppose that alcohol must be highly combustible, since it contains so large a proportion of hydrogen?

MRS. B.

Extremely so; and it will burn at a very moderate temperature.