The properties of alcohol are the following: It is a transparent liquor of an agreeable flavour, and may be changed in this particular, by essential oils. It may be exposed to a low temperature without freezing. It boils at 106°, when of the specific gravity .820, and in a vacuum at 56°. It has a strong affinity for water, with which it combines in any proportion; and the specific gravity varies according to the proportion of the mixture and the temperature, on which are founded the tables of Blagden, Gilpin, and others.
Neither common air, nor oxygen, has any action on alcohol at moderate temperatures, whether in a liquid or aeriform state. On hydrogen, carbon, and charcoal, it has little or no action, but on phosphorus it acts, a portion of which it dissolves. With sulphur, it may be made to unite, as also with the alkalies, but not with the earths, except strontian and barytes. It is decomposed by sulphuric and nitric acids, with both of which it forms ether. It dissolves some salts, and has scarcely any effect upon others. Lastly, it dissolves resins and essential oils; but it neither acts upon gums, properly so called, nor on fixed oils. It is a compound of hydrogen, carbon, and a small proportion of oxygen, and may be decomposed, by passing its vapour through an ignited porcelain tube.
Alcohol, by its combustion, as it is used in spirit-lamps for chemical and other purposes, produces no smoke, in consequence of the carbon it contains being totally converted, during that process, into carbonic acid; and its hydrogen, uniting with another portion of the oxygen of the atmospheric air, passes off in the form of aqueous vapour. Alcohol, used in this way, is preferable to oil; for the latter produces a large quantity of smoke, unless it is burnt in the Argand lamp. Alcohol is inflamed, when it is brought in contact with an ignited body. The combustion is rapid without any residue, and the flame white.
As to the strength of alcohol, the best means of determining it, is with the hydrometer; but usually its proof is ascertained by means of gunpowder. A portion of powder, put into a cup, and alcohol poured on it and inflamed, will, if the latter be strong, be set on fire; if, however, the powder should not take fire, but the flame of the alcohol be extinguished, we infer the existence of water, and that the alcohol is not of the proper strength. This experiment is founded on this circumstance, that, if the alcohol contains water, after the alcoholic portion is all consumed, the water will not only extinguish the flame, but also prevent the inflammation of the powder. The hydrometer, however, is the best experiment, as it determines at once the fact of the strength of the liquor.
Alcohol is used in the preparation of certain fulminating substances, as fulminating mercury and silver in particular; the preparation of which, we will give in the two next sections.
It may not be improper to mention another application of alcohol, that of forming the aphlogistic lamp, or lamp that burns without flame. The following description of it, is given by Accum, in his Chemical Amusements, Am. Ed. p. 355. "In a common lamp, with a wick of about half a dozen common threads of cotton wick, used for lamps, put some good spirit of wine. Dispose the threads of wick, not intertwined, but straight and parallel to each other. Take platina wire of the thickness of 1/100th part of an inch; coil it round the wick, about nine coils below, and six coils standing above the top of the wick; the diameter or width of the coils should not be more than 3/20th, or 1/7th of an inch wide. Light the wick; and, when the coil of platina above the wick is red-hot, blow out the flame. There will then be a current of pure alcohol, gradually rising from the reservoir below, through the wick, sufficient to keep the upper coil of platina red-hot, until the whole of the alcohol is consumed. This lamp has kept constantly lighted during sixty hours. By means of it, a match, a bit of spunk, or candle may be lighted when wanted. The quantity of alcohol consumed is not much: about an ounce, or an ounce and a half during the night, from bed-time until morning will suffice." This article was added to Accum by Dr. Cooper. A figure of the lamp is in Brande's Chemistry. Dr. Comstock has a paper on the aphlogistic or flameless lamp, in Vol. IV. p. 328, of Silliman's Journal of Science and Arts, which contains some judicious and useful remarks. Sir H. Davy (Journal of the Royal Institution) has discovered, that the vapour of camphor answers the same purpose as alcohol. If a platinum wire be heated and laid upon camphor, it will continue to glow as long as any remains, and the wire will frequently light it up into flame. Davy found, that, in the slow combustion of alcohol, &c. an acid was generated, to which he gave the name of Lampic acid. Faraday and Daniel (Journal of Science and the Arts) have confirmed his conclusions.
Dr. Marcet has proposed a method of producing an intense heat, by causing a current of oxygen gas to pass through the flame of alcohol. The construction of the lamp and gas-holder may be found in the Archives des Découvertes, Vol. vii, p. 61.
Sect. XXV. Of Fulminating Mercury.
As the fulminating mercury of Howard consists principally of the oxalate of mercury, the oxalate of this metal may be employed for the same purpose. Oxalic acid does not act on mercury, but dissolves its oxide, and forms with it a white powder. I formed various fulminating metallic powders, (See Coxe's Medical Museum), and prepared one in particular by merely digesting a solution of the salt of sorrel (superoxalate of potassa) on red precipitate. The effect is that the oxalic acid unites with the oxide of mercury, and forms an oxalate of mercury, which, when struck with a hammer, produces a detonation. Oxalate of mercury, possessing the same effects, may be formed, very expeditiously, by pouring the oxalate, or the superoxalate of potassa into a solution of nitrate of mercury. The oxalate of mercury will be precipitated, which is to be caught on a filter, washed, and dried in a gentle heat.