Cooley's Cyclopaedia of Practical Receipts Volume I Part 31

In _chemistry_, a term invented, by Berzelius, to express the state or condition, or the change of character, a.s.sumed by certain substances at different temperatures, or under different treatment, whilst their nature and composition continue the same. It more particularly relates to colour, hardness, solubility, texture, &c. Boron, carbon, silicon, iron, sulphur, and phosphorus, afford striking examples of the changes here referred to.

=ALLOX'ANTIN.= C_{8}H_{4}N_{4}O_{7}.3H_{2}O. A crystallisable substance, first obtained by Dr Prout from uric acid.

_Prep._ 1. Uric acid, 1 part; is boiled in water, 32 parts; dilute nitric acid being added until solution is complete; the resulting liquid is evaporated to 2/3rds its volume, and then set aside for 10 or 12 hours; the crystals, which are deposited, are purified by re-solution and crystallisation.

2. Sulphuretted hydrogen gas is pa.s.sed, in a full stream, through a moderately strong aqueous solution of alloxan, in the cold. The alloxantin, which is deposited as a crystalline ma.s.s, is purified by draining, cautious washing with cold water, re-solution in boiling water, and re-crystallisation. The impure mother-liquor from which crystals of alloxan have separated, if diluted with water, may be used for this purpose.

_Prop., &c._ Crystals, small colourless, transparent, four-sided, oblique rhombic prisms; scarcely soluble in cold water; solution reddens litmus; with baryta water it gives a characteristic violet-coloured precipitate, which disappears on heating; and with nitrate of silver a black precipitate of that metal; the crystals are reddened by ammoniacal vapours.

=ALLOY'.= _Syn._ ALLIAGE, Fr.; LEGIRUNG, VERMISCHUNG DURCH SCHMELZEN, Ger.

In _coinage_, a compound of the precious metals with another, or others, of less value; also the least valuable metal, or metals, in such compounds. In _chemistry_ and _metallurgy_, combinations of the metals with each other usually obtained by fusion. When mercury is one of the component metals, the compound is termed an AMALGAM.

_Prep., &c._ No General rules can be given for this purpose. Alloys of metals differing greatly in fusibility, are commonly made by adding the more fusible one, either in the melted state, or in small portions at a time, to the other melted, or heated to the lowest possible temperature at which a perfect union will take place between them. The mixture is usually affected under a flux, or some material that will promote liquefaction, and prevent volatilisation and unnecessary exposure to the air. Thus, in melting lead and tin together, for solder, resin, or tallow is thrown upon the surface; in tinning copper, the surface is rubbed with sal ammoniac; and in combining some metals, powdered charcoal is used for the same purpose. Quicksilver combines with many metals in the cold, forming AMALGAMS.

_Comp._ The following _Table_ exhibits the composition of the more important compounds of this cla.s.s:--

_Table of the princ.i.p.al Alloys._[27]

NAMES. COMBINING METALS.

ALBATA See German Silver.

AMALGAMS Mercury and other metals.

BATH-METAL Copper and zinc.

BELL-METAL Copper and tin.

BRa.s.s Copper and zinc.

BRITANNIA METAL Tin with antimony, copper, and bis.m.u.th.

BRONZE Tin and copper.

BRONZE ALUMINIUM Copper and aluminium.

CANNON-METAL Tin and copper.

DUTCH GOLD Copper and zinc.

FUSIBLE METAL Bis.m.u.th, lead, and tin.

GERMAN SILVER Copper, nickel, and zinc, with, sometimes, a little iron and tin.

GOLD (_standard_) Gold with copper.

GOLD (_old standard_) Gold with copper and silver.

GUN-METAL See Cannon-metal.

MOSAIC GOLD Copper and zinc.

OR-MOLU Copper and zinc.

PEWTER (_common_) Tin and lead.

PEWTER (_best_) Tin with antimony, bis.m.u.th and copper.

POT-METAL, c.o.c.k-METAL Copper and lead, with, sometimes, a little zinc.

QUEEN'S METAL Tin with antimony, bis.m.u.th, and copper.

SHOT-METAL Lead with a little a.r.s.enic.

SILVER (_standard_) Silver and copper.

SOLDER Tin and lead.

SPECULUM-METAL Tin and copper, and a.r.s.enic.

STEREOTYPE-METAL Lead, antimony, and bis.m.u.th.

TOMBAC, RED TOMBAC Copper and zinc.

TUTANIA See Britannia metal.

TYPE-METAL Lead and antimony.

WHITE COPPER (_Packfong_; Copper and a.r.s.enic.

_Whitetombac_)

[Footnote 27: For the proportions of the component metals, refer to the alloys under their respective heads.]

_Prop., &c._ Alloys generally possess characteristics unshared by their component metals. Thus, copper and zinc form bra.s.s, which has a different density, hardness, and colour to either of its const.i.tuents. Whether the metals tend to unite in atomic proportions, or in any definite ratio, is still undetermined. The evidence afforded by the natural alloys of gold and silver, and by the phenomena accompanying the cooling of several alloys from the state of fusion, goes far to prove that such is the case.

(Rudberg.) The subject is, however, one of considerable difficulty, as metals and metallic compounds are generally soluble in each other, and unite by a simple fusion and contact. That they do not combine indifferently with each other, but exercise a species of elective affinity not dissimilar to other bodies, is clearly shown by the h.o.m.ogeneity and superior quality of many alloys in which the const.i.tuent metals are in atomic proportions. The variation of the specific gravity and melting-points of alloys from the mean of those of their component metals, also affords strong evidence of a chemical change having taken place.

Thus, alloys generally melt at lower temperatures than those required for their separate metals. They also usually possess more tenacity and hardness than the mean of their const.i.tuents.

Matthiessen found that when weights are suspend to spirals of hard-drawn wire made of copper, silver, gold, or platinum, they become nearly straightened when stretched by a moderate weight; but wires of equal dimensions composed of copper-tin (12% of tin), silver-platinum (36% of platinum), and gold-copper (84% of copper), scarcely undergo any permanent change in form when subjected to tension by the same weight.

The same chemist gives the following approximative results upon the tenacity of certain metals and wires hard drawn through the same gauge (No. 23):

Breaking strain for:

lbs.

Copper 25-30 Tin under 7 Lead " 7 Tin-lead (20% lead) about 7 Tin-copper (12% copper) " 7 Copper-tin (12% tin) " 80-90 Gold 20-25 Gold-copper (84% copper) 70-75 Silver 45-50 Platinum 45-50 Silver-platinum (30% platinum) 75-80

On the other hand, their malleability, ductility, and power of resisting oxygen is generally diminished. The alloy formed of two brittle metals is always brittle; that of a brittle and a ductile metal, generally so; and even two ductile metals sometimes unite to form a brittle compound. The alloys formed of metals having different fusing-points are usually malleable whilst cold, and brittle whilst hot. The action of the air on alloys is generally less than on their simple metals, unless the former are heated. A mixture of 1 part of tin and 3 parts of lead is scarcely acted on at common temperatures; but at a red heat it readily takes fire, and continues to burn for some time like a piece of bad turf. In like manner, a mixture of tin and zinc, when strongly heated, decomposes both moist air and steam with almost fearful rapidity.

The specific gravity of alloys is never the arithmetical mean of that of their const.i.tuents, as commonly taught; and in many cases considerable condensation or expansion occurs. When there is a strong affinity between two metals, the density of their alloy is generally greater than the calculated mean; and _vice versa_, as may be seen in the following Table:--

_Alloys having a density_--

Greater than the mean of Less than the mean their const.i.tuents:-- of their const.i.tuents:--

Copper and bis.m.u.th, Gold and copper, " palladium, " iridium, " tin, " iron, " zinc, " lead, Gold and antimony, " nickel, " bis.m.u.th, " silver, " cobalt, Iron and antimony, " tin, " bis.m.u.th, " zinc, " lead, Lead and antimony, Nickel and a.r.s.enic, Palladium and bis.m.u.th, Silver and copper, Platinum and molybdenum, Tin and antimony, Silver and antimony, " lead, " bis.m.u.th, " palladium, " lead, Zinc and antimony.

" tin, " zinc.

"Every alloy," says Dr Ure, "is, in reference to the arts and manufactures, a new metal, on account of its chemical and physical properties. A vast field here remains to be explored. Not above sixty alloys have been studied by chemists, out of many hundreds which may be made, and of these very few have yet been practically employed. Very slight modifications often const.i.tute very valuable improvements upon metallic bodies." See a.n.a.lYSIS, a.s.sAYING, BRa.s.s, BRONZE, ELECTROTYPE, GERMAN SILVER, GOLD, METALS, SPECIFIC GRAVITY, &c.

=ALL'SPICE.= See PIMENTO.

=ALLU"VIAL.= (-l'oov'-yal). _Syn._ ALLU"VIOUS*; ALLU"VIUS, L.; D'ALLUVION, Fr. In _geology_, applied to partial deposits of mud, sand, gravel, &c., left by rivers and floods upon land not permanently submerged beneath water; in _agriculture_, applied to soils so formed or deposited.

=ALLU"VIUM.= [L., Eng.] _Syn._ ALLUVION, Fr.; ANFLoSSUNG, ANSCHWEMMUNG, Ger. In _geol._ and _agr._, alluvial deposit or soil. See SOILS, &c.

=AL'LYL= (-lil). C_{3}H_{5}. In _chemistry_, the radical of the essential oils containing sulphur, as those of a.s.saftida, garlic, horseradish, mustard, onions, &c., which are either sulphides or sulphocyanides of allyl. Its probable existence was first shown by Captain Reynolds, who succeeded in producing several of its derivatives. It has since been obtained, in a separate state, by the action of sodium upon iodide of allyl. It is an oily substance with a high boiling point.

=Allyl, Sulphide of=, (C_{3}H_{5})_{2}S; obtained (artificially) by acting on sulphocyanide of allyl with sulphide of pota.s.sium. See OIL OF GARLICK.

=Allyl, Sulphocy'anide of=, C_{3}H_{5}CNS; obtained by submitting iodide of allyl to the action of sulphocyanide of pota.s.sium; or by gently heating a mixed alcoholic solution of sulphide of allyl and bichloride of mercury, with sulphocyanide of pota.s.sium. See OIL OF MUSTARD (VOLATILE).

=AL'MOND= (ah'-mund). _Syn._ AMYG'DALA (also -US, -UM*), L.; AMANDE, Fr.; MANDEL, Ger., Dut., Dan., Swed. The 'almond-tree' (_amyg'dalus commu'nis_--Linn.; Ph. L., E., and D.; _Amandier_--Fr.), a tree of the nat. ord. Rosaceae, indigenous to Persia, Syria, and the north of Africa; but also extensively cultivated in southern Europe. The almond-tree is about the size of the peach-tree, which it much resembles in appearance.

It is incapable of ripening its fruit in this country, and is, therefore, only grown here for the sake of its beautiful vernal flowers. There are several varieties, of which the most important are the sweet and the bitter, so named from the flavour of the seed or kernel. These, for the most part, resemble each other in appearance. De Candolle ('Prodromus,'

ii, 530) gives five varieties of this species:--A. AMA"RA (_bitter-almond_); A. DUL'CIS (_sweet-a._); A. FRAGILIS (_tender-sh.e.l.led a._); A. MACROCAR'PA (_large-fruited a._, _pista'chio a._, _sultana a._); A. PERSICO'DES (_peach a._).

=Almond, Per'sian.= The peach.

=AL'MONDS=. _Syn._ AMYG'DALae, L.; AMANDES, Fr.; MANDELN, Ger. The seed or kernels of the almond-tree. They are met with in commerce both in the sh.e.l.l (AMYG'DALae c.u.m PUTAM'INE, -in-e, L.), and sh.e.l.led (AMYGDALae, L.). In the retail shops, most commonly in the latter form. Those rancid, broken, or worm-eaten should be rejected.