Vinegar is never used for the preservation of butcher meat, but salmon is often pickled in it, with the addition of salt and spices.
Pyrolignic acid has lately been much extolled, as having a specific power in preserving animal mat ters. It consists of acetic acid, impregnated with an empyreumatic oil. The acid is in general very strong, and being free from the mucilage which promotes the spoiling of common vinegar, it is so far a better antiseptic ; but the empyreumatic oil may also add to its powers, either by keeping away insects, to which it is very offensive, or by a direct antiseptic power not understood. Professor Jiirg of Leipsic is said to have recovered tainted flesh by rubbing it with the oil separated from the acid ; and there is no doubt that the smoking of beef, hams, salmon, and herrings, makes them keep longer than the mere drying, and the degree of previous salting, would lead us to expect.
Sugar has also the power of preserving vegetable substances from decay, but, on account of its expence, it is only used for fine fruits and aromatic sub stances. The preservation of these by means of sugar constitutes a principal part of the art of con fectionary, and attention to many minutiae is neces sary for the success of each preparation. The most general principles only can be noticed here.
Vegetable substances may be either preserved in syrup or candied ; or their juices may be employed in making syrups, jellies, or fruit-cakes. The art of confectionary is very difficult, and to attain per fect success, requires attention to many particulars, which at first seem frivolous and even improper, but which have been found by experience to be es sential. The clarification and boiling of the sugar to its proper degree is of primary importance, and has not perhaps been sufficiently examined by scien tific men.
A weak syrup has a tendency to ferment, and quickly becomes sour if kept in a temperate degree of heat ; it is therefore not calculated to prevent the natural fermentation of vegetable juices, which always increase its tendency to corrupt. Pharma ceutists have ascertained that a solution, prepared by dissolving two parts of double refined sugar into one of water, or any watery fluid, and boiling the solution a little, forms a syrup, which neither fer ments nor crystallizes ; and the proportion may be considered as the basis of all syrups, and seems to be the degree of boiling syrup called smooth by the confectioners, as exemplified in their Syrups de Ca pillaire, Orgeat, &c.
Sugar is equally powerful in preserving animal sub stances from putrefaction. As a novelty to modern artists, we translate from their great precursor, Caelius Apicius, a method of preserving meat at any time without salt : " Let fresh meat of any kind be co vered with honey ; but hang up the vessel, and use it when you please. This succeeds better in winter; but will last a few days in summer. The same may be done with meat that has been cooked." (Lib. I. cap. 8.) Other methods of preserving food have been tried, but rather as a matter of curiosity than utility.
The property of charcoal, to restore sweetness to flesh beginning to be tainted, was first pointed out by M. Lowitz in Petersburg, in 1786 (Crell's An nals), who made numerous experiments upon the subject. For their success, it is necessary that the charcoal have been recently burnt, and that it be ap plied in a certain quantity. Too little fails in its ef fect, and too much affects the nature of the sub stance upon which it acts. By some it has been supposed to act merely mechanically, by absorbing fluid and putrescent exudations ; but it is more pro bable, that it acts chemically, by absorbing oxygen gas from the air in contact with the meat. In the 4th volume of the Journal of Science, p. 367, there is an account of some successful experiments, in which alternate layers of meat and charcoal were packed in canisters, previously filled with carbonic gas, and then carefully luted up, and covered with bladder.
In the Journal de Pharmacie for September 1818, M. Raymond, Professor of Chemistry at Lyons, has related some experiments which he made upon the an tiseptic properties of chlorine. Beef; exposed to the action of this gas for a few minutes, underwent no change in the course of six months, except becom ing dry from the action of air and time. A Guinea pig, suffocated in the same gas, and afterwards im mersed for a few minutes in water saturated with chlorine, and then exposed to the air for four months, without having its entrails removed, show ed no sign of putrefaction in four months. He also found that tainted meat recovered the smell and ap pearance of fresh meat by being immersed in liquid chlorine.