686 PYEOXYLIC SPIRIT 



the two is very slight. Its melting-point is 318 Fahr. It sublimes at 300 in free 

 air; heated in a close tube in a bath of mercury, it emits vapour at 400 ; it then begins 

 to decompose, and is totally decomposed at 500. Sulphuric acid decomposes it, 

 producing a beautiful blue colour, which passes into crimson, as the acid attracts 

 water from the atmosphere, and it totally disappears on plentiful dilution with water, 

 leaving carbon of a dirty brown colour. Its alcoholic or turpentine-solution imparts 

 a permanent yellow dye to vegetable- or animal- matter. 



Pyroxanthine consists, according to the analysis of Drs. Apjohn and Gregory, of 

 carbon, 75'275; hydrogen, 5 - 609 ; oxygen, 19-116, in 100 parts. 



P YROXYLIC SPIRIT. Syns. Pyroligneous spirit, Pyroligneous ether, Wood-spirit, 

 Wood-naphtha, Methylic alcohol, Hydrate of methyle, Hydrated oxide of methyle. 

 C 2 H 4 2 = C 2 H 3 0,HO (CHO). Density of strongest wood-spirit at 32, 0-8179. 

 Density at 68, 0'798. Density of vapour, 1-12 = 4 volumes. Boiling-point, 150Fahr. 



Wood-spirit was first recognised as a distinct substance by Taylor, in 1812. Its 

 true nature, however, was unknown until the appearance of the important research of 

 MM. Dumas and Peligot, in 1835. 



Pyroxylic spirit is obtained from the liquid products of the distillation of wood by 

 taking advantage of its superior volatility. The crude wood-vinegar, if distilled per 

 se, yields up to a certain point highly impure and weak spirit. It is, however, free 

 from ammonia and alkaloids. If, on the other hand, the vinegar is first neutralised 

 by lime or soda previous to the distillation of the spirit, it is rendered more free from 

 acetate of methyle and some other impurities, but it then contains alkaloids and 

 ammonia. At times the quantity of the latter substance present is so large that the 

 spirit smokes strongly on the approach of a rod dipped in hydrochloric or acetic acid. 

 In order to apply this test, it is obvious that the hydrochloric acid must be diluted until 

 it does not fume by itself. By repeated rectifications over lime or chalk, rejecting 

 the latter portions, the wood-spirit may be obtained colourless, and of a strength 

 varying from 80 to 90 per cent, of pure spirit, the specific gravity being from 0-870 

 to 0-830. 



Inasmuch as wood-spirit boils at a temperature far less than the point of ebullition 

 of the impurities ordinarily found in it, it may always be greatly improved in solvent 

 power, appearance, and odour, by mere rectification on the water-bath or in a recti- 

 fying-still. But, nevertheless, a certain quantity of the more volatile impurities 

 always accompany the methylic alcohol, being carried over with its vapour. Among 

 the foreign bodies may be mentioned the hydrocarbons of the benzole series. These 

 may be entirely removed by mixing the crude spirit with three or four times its 

 volume of water ; the hydrocarbons are thus rendered insoluble and rise to the surface 

 of the fluid. By means of a separator the lower layer may be removed, and after two 

 or three rectifications, at as low a temperature as possible, the spirit may be procured 

 quite clean. 



To obtain wood-spirit quite pure it is generally recommended to mix it with 

 chloride of calcium, and again rectify on a steam- or water-bath. By operating in 

 this manner, the methylic alcohol combines with the chloride of calcium, forming a 

 compound not decomposable at the temperature of the water-bath. The impurities 

 present therefore distil away, leaving in the still a compound of pure methylic alcohol 

 with chloride of calcium. But this latter compound possesses little stability, and 

 may be decomposed by the mere addition of water, which liberates the spirit. It is 

 then to be distilled away from the salt, and after one or two rectifications over quick- 

 lime will be quite pure. 



It is highly important that wood-spirit should be of considerable purity if required 

 for the purpose of dissolving the gums. It is true, that so far as its use for dissolving 

 shellac is concerned, there is no need for extreme purity, as shellac will dissolve 

 in most specimens of wood-spirit. But it is not in this case the mere solvent power 

 that is required ; for if a solution of shellac in impure wood-spirit be employed by 

 hatters, the vapour evolved is so irritating to the eyes that the workmen are unable to 

 proceed. If the spirit has the property of fuming on the approach of a rod dipped 

 in acetic or hydrochloric acids, it may be taken for granted that it will be incapable 

 of dissolving gum-sandarach. This arises from the fact that such spirit has been 

 distilled from an alkaline base, such as lime or soda, and contains alkaloids, ammonia, 

 and various other impurities which destroy its solvent power. The alkaline reaction 

 may be destroyed and the spirit rendered fit for use by adding 2 or 3 per cent, of 

 sulphuric acid and then distilling. The alkaloids and many other impurities will 

 then be retained, and the spirit may either be used at once or still further purified 

 by dilution with water and subsequent rectification. It is possible to combine the 

 two processes at one operation, by diluting the spirit, with four times its bulk of water, 

 and adding just enough oil of vitriol to the diluted liquid to give it a faint acid 

 reaction to litmus-paper. It is absolutely essential to the success of this process 

 that the mixture of spirit, water, and acid be perfectly well mixed. 



