66 ALEMBROTH 



exceeding 80 F., will consist of pure aldehyde. Aldehyde is a, colourless, very 

 volatile, and mobile fluid, having the density 0-800 at 32. It boils, under ordinary 

 atmospheric pressure, at 70 F. Its vapour density is 1-332. Its formula corre- 

 sponds to four volumes of vapour ; we consequently obtain the theoretical vapour 

 density by multiplying its atomic weight = 44 by half the density of hydrogen, or 

 0346. The number thus found is 1*5224, corresponding as nearly as could bo 

 desired to the experimental result. 



Aldehyde is produced in a great number of processes, particularly during the de- 

 structive distillation of various organic matters, and in processes of oxidation. From 

 alcohol aldehyde may bo procured by oxidation with platinum black, nitric acid, 

 chromic acid, chlorine (in presence of water), or, as we have seen, a mixture of 

 peroxide of manganese and sulphuric acid. Certain oils, by destructive distillation, 

 yield it Wood vinegar in the crude state contains aldehyde as well as wood-spirit. 

 Lactic acid, when in combination with weak bases, yields it on destructive distilla- 

 tion. Various animal and vegetable products afford aldehyde by distillation with 

 oxidizing agents, such as sulphuric acid and peroxide of manganese, or bichromate 

 of potash. 



The word aldehyde, like that of alcohol, is gradually becoming used in a much 

 more extended sense than it was formerly. By the term is now understood any 

 organic substance which, by assimilating two atoms of hydrogen, yields a substance 

 having the properties of an alcohol, or, by taking up two atoms of oxygen, yields 

 an acid. It is this latter property which has induced certain chemists to say 

 that there is the same relation between an aldehyde and its acid as between inorganic 

 acids ending in ous and io. Several very interesting and important substances are 

 now known to belong to the clasa of aldehydes. The essential oils are, in several 

 instances, composed principally of bodies having the properties of aldehydes. Among 

 the most prominent may be mentioned the oils of bitter almonds, cumin, cinnamon, 

 rue, &c. Now that the character of the aldehydes is becoming better understood, 

 the chances of artificially producing the essential oils above alluded to in the com- 

 mercial scale become greatly increased. A substitute for one of them has been for 

 some years known under the very incorrect name of artificial oil of bitter almonds. 

 See NITBOBENZOLE. C. G. W. 



AXiDEHVDE GREEN, Aniline Green, or Emeraldine. This dye was discovered 

 in 1863 by M. Cherpin, of Saint Ouen, and is employed for dyeing silk ; the colour 

 is especially brilliant by candle-light. It may be conveniently prepared by adding 

 one-half part of aldehyde to a cold solution of one part of magenta in three of strong 

 sulphuric acid, and one of water. This mixture, when heated, yields an unstable 

 blue substance known as aldehyde blue. By pouring this into a large bulk of boiling 

 water containing about three or four times as much hyposulphite of soda as magenta 

 originally employed, and then boiling and filtering the product, the aldehyde green 

 will be obtained in the filtrate. See ANILINE. 



.AXDER. (Aune, Fr. ; Erie, Ger. ; Alnus glutinosa, Lin.) A tree, different species 

 of which are indigenous to Europe, Asia, and America. The common alder seldom 

 grows to a height of more than 40 feet. The wood is stated to be very durable under 

 water. The piles at Venice, and those of Old London Bridge, are stated to have 

 been of alder ; and it was much used for pipes, pumps, and sluices. The charcoal of 

 this wood is used for gunpowder. 



The fermented infusion of pale malted barley, combined with infusion of 

 hops. See BEEB. 



ALEMBIC. A Still. See DISTILLATION. The 

 term is, however, applied to a still of peculiar con- 

 struction, in which the head, or capital, is a separate 

 piece, fitted and ground to the neck of the boiler, or 

 cucurbit, or otherwise carefully united with a lute. 

 The alembic has this advantage over the common 

 retort, that the residue of distillation may be easily 

 cleared out of the body. It is likewise capable, when 

 skilfully managed, of distilling a much larger quantity 

 of liquor in a given time than a retort of equal 

 capacity. In France the term alembic, or rather 

 alambic, is used to designate a glass still. 



ALEMBROTH, SALT OP. (Sal Alcmbroth.) 

 The talt of wisdom of the alchemists ; a compound of bichloride of mercury and 

 sal ammoniac. If two atoms of bichloride of mercury are mixed with one atom of 

 sal ammoniac and eight atoms of water, at 140 this mixture is fluid, but the salt of 

 alembroth crystallises on cooling. 



