38

ALMOND OIL.

elaborate researches on metallic alloys, that gold made standard with the usual precautions, by silver, copper, lead, antimony, &c., and then cast, after long fusion, into verticalbars, was by no means a uniform compound; but that the top of the bar, correspondingto the metal at the bottom of the crucible, contained the larger proportion of gold.Hence, for a more thorough combination, two red-hot crucibles should be employed, andthe liquefied metals should be alternately poured from the one into the other. To pre-vent unnecessary oxydizement from the air, the crucibles should contain, besides themetal, a mixture of common salt and pounded charcoal. The metallic alloy should alsobe occasionally stirred up with a rod of pottery ware. '

The most direct evidence of a chemical change having been effected in alloys is, whenthe compound melts at a lower temperature than the mean of its ingredients. Iron,which is nearly infusible, acquires almost the fusibility of gold when Alloyed with thisprecious metal. The analogy is here strong with the increase of solubility which saltsacquire by mixture, as is exemplified in the difficulty of crystallizing residuums of salinesolutions, or mother waters, as they are called.

In common cases the specific gravity affords a good criterion whereby to judge of theproportion of two metals in an alloy. But a very fallacious rule has been given in somerespectable works for computing the specific gravity that should result from the alloyingof given quantities of two metals of known densities, supposing no chemical condensationor expansion of volume to take place. Thus, it has been taught, that if gold and copperbe united in equal weights, the computed specific gravity is merely the arithmeticalmean between the numbers denoting the two specific gravities. Whereas the specificgravity of any alloy must be computed by dividing the sum of the two weights by the)um of the two volumes, compared, for convenience sake, to water reckoned unity. Or,in another form, the rule may be stated thus :—Multiply the sum of the weights intothe products of the two specific-gravity numbers for a numerator; and multiply eachspecific gravity-number into the weight of the other body, and add the two productstogether for a denominator. The quotient obtained by dividing the said numerator bythe denominator, is the truly computed mean specific gravity of the alloy. On com-paring with that density, the density found by experiment, we shall see whether expan-sion or condensation of volume has attended the metallic combination. Gold having aspecific gravity of 19-36, and copper of 8-87, when they are alloyed in equal weights, give,

• 19*36 ] 8*87

by the fallacious rule of the arithmetical mean of the densities i-IL- = 14-11;

whereas the rightly computed mean density is only 12-16. It is evident that, on com-paring the first result with experiment, we should be led to infer that there had been aprodigious condensation of volume, though expansion has actually taken place. LetW, w be the two weights;'?, p the two specific gravities, then M, the mean specificgravity, is given by the formula—

(W + w) Pp _ (P—p )2

Pw + pW " 2 A = - F+P = tWiCe

M = ■

the error of the arithmetical mean ; which is therefore always in excess.

ALMOND. (Jlmaiuk, Fr.; Mandel, Germ.) There are two kinds of almond whichdo not differ in chemical composition, only that the bitter, by some mysterious re-actionof its constituents, generates in the act of distillation a quantity of a volatile oil, whichcontains hydrocyanic acid. Vogel obtained from bitter almonds 8-5 per cent, of husks.After pounding the kernels, and heating them to coagulate the albumen, he procured,by expression, 28 parts of an unctuous oil, which did not contain the smallest particleof hydrocyanic acid. The whole of the oil could not be extracted in this way. Theexpressed mass, treated with boiling water, afforded sugar and gum, and, in consequenceof the heat, some of that acid. The sugar constitutes 6-5 per cent, and the gum 3. Thevegetable albumen extracted, by means of caustic potash, amounted to 30 parts; thevegetable fibre to only 5. The poisonous aromatic oil, according to Robiquet and Bou-tron-Charlard,does not exist ready-formed in the bitter almond, but seems to be producedunder the influence of ebullition with water. These chemists have shown that bitter al-monds deprived of their unctuous oil by the press, when treated first by alcohol, and thenby water, afford to neither of these liquids any volatile oil. But alcohol dissolves out apeculiar white crystalline body, without smell, of a sweetish taste at first, and afterwardsbitter, to which they gave the name of amygdaline. This substance does not seem con-vertible into volatile oil.

Sweet almonds, by the analysis of Boullay, consist of 54 parts of the bland almond oil,6 of uncrystallizable sugar, 3 of gum, 24 of vegetable albumen, 24 of woody fibre, 5 ofhusks, 3 o of water, 0-5 of acetic acid, including loss. We thus see that sweet almondscontain nearly twice as much oil as bitter almonds do.

ALMOND OIL. A bland fixed oil, obtained usually from bitter almonds by the ac-tion of a hydraulic press, either in the cold, or aided by hot iron plates. See Oil.