COPPER.

339

An alloy of ioo of copper and 4'17 of tin has teen proposed by M. Cnaudei for til-ready manufacture of medals. After melting this alloy, he casts it in moulds made ofsuch bone-ash as is used for cupels. The medals are afterward subjected to the actionol the coining press, not for striking them, for the mould furnishes perfect impressions,but for finishing and polishing them.

By a recent analysis of M. Berthier, the bells of the penduks, or ornamental clocks,made in Paris , are found to be composed—of copper 72-00, tin 26-56, iron 1-44, in 100parts.

An alloy of 100 of copper and 14 of tin is said by M. Dussaussy to furnish tools, which,hardened and sharpened in the manner of the ancients, afford an edge nearly equal to‘hat of steel.

Cymbals, gongs, and the tamtam of the Chinese are made of an alloy of 100 of copperWl ‘h about 25 of tin. To give this compound the sonorous property in the highest de-? ree > it must be subjected to sudden refrigeration. M. D’Arcet, to whom this discovery‘s due, recommends to ignite the piece after it is cast, and to plunge it immediately intocold water. The sudden cooling gives the particles of the alloy such a disposition,that, with a regulated pressure by skilful hammering, they may be made to slide over each°‘her, and remain permanently in their new position. When by this means the instru-bjcnt has received its intended form, it is to be heated and allowed to cool slowly in the? lr - The particles now take a different arrangement from what they would have doneby sudden refrigeration ; for instead of being ductile, they possess such an elasticity,

that

after

on being displaced by a slight compression, they return to their primary positionalter a series of extremely rapid vibrations ; whence a very powerful sound is emitted.r °nze, bell-metal, and probably all the other alloys of tin with copper, present the same

Peculiarities.

v iT^a.a^oy 100 of copper with from 60 to 33 of tin forms common bell-metal. It isThe ° r S ra >> brittle, and sonorous, but not so much so as the preceding.

bell

!? bmtal of house-clock bells contains a little more tin than that of church-bells, and the

bf a repeater contains a little zinc in addition to the other ingredients.

r^, — ■»jy<-atci iajiiluiiis a. untc 41111; in auumuii iu un; mnci. 11151. cuiculs«

0 j. " e bronze-founder should study to obtain a rapid fusion, in order to avoid the causesU o^‘b indicated above. Reverberatory furnaces have been long adopted for this opera-are ’ and amon ? these, the elliptical are the best. The furnaces with spheroidal domestne l ( Use< i by the bell-founders, because their alloy being more fusible, a more moderatebon * leat * s re Q u i re( l > however, as the rapidity of the process is always a matter of.^beuce, they also would find advantage in employing the elliptical hearths, (see theUni,, ^e melting furnace, as fi.gured under Smelting of copper ores.) Coal is noworsally preferred for fuel.

I41 ® ahoy of 100 of copper with 50 of tin, or more exactly of 32 of the former withThis t le Walter, constitutes speculum metal, for making mirrors of reflecting telescopes,bant Co ™P ou ud is nearly white, very brittle, and susceptible of a fine polish with a bril-briace. The following compound is much esteemed in France for making specula,bbghlv l )ai ts P ure c0 PP er and 1 of grain-tin in separate crucibles, incorporate thor-is the o^ 11 * 1 a Wooden spatula, and then run the metal into moulds. The lower surfacejJjr ‘bat should be worked into a mirror.

Ulahin J: ' c '' Br ards, in the Nautical Almanack for 1787, gave the following instructions forspeculum metal. /

P 0r tion^ r ^ le C0 PP er to be tried by making a series of alloys with tin, in the pro-

the prop 0 * °* ‘be former to 47, to 48, to 49, and to 50 of the latter metal; whence‘he allovh 10 - 18 ""'Bitest compound may be ascertained. Beyond the last proportion,mined tj,-. ‘. ns to I° se in brilliancy of fracture, and to take a bluish tint. Having deter-silver, cov lfl be 32 parts of the copper, melt, and add one part of brass and as muchItlel ‘ e d, sti Cn ?-" tlle Sl,r ‘ ace of tlle mixture with a little black flux; when the whole is*ed by ’the r VVlt '* a wo °den rod, and pour in from 15 to 16 parts of melted tin (as indica-c °ld Water b r jT ara ‘°ry trials), stir the mixture again, and immediately pour it out intoP°Und 1 _ ‘ p en melt again at the lowest heat, adding for every 16 parts of the corn-bottom 0 f t ]j 0 "’bite arsenic, wrapped in paper, so that it may be thrust down to theP°nr it ; n . ® '-rucible. Stir with a wooden rod as long as arsenical fumes rise, and then

,?> ‘hat it rr, a ■ mou ^- While still red hot, lay the metal in a pot-full of very hot em-s Plinters is tu-pvmf 0 ?^ Ver - s I°wly, whereby the danger of its cracking or flying into

tiaviner ^‘’evented.

°S Se l )a rating < th' >e< * t ' le different alloys of copper and tin, I shall now treat of the methodobt - • The procp? 6 me .‘ a * s bom each other as they exist in old cannons, damaged bells,„ mining comerf™ v ^ on a ver 5' great scale in France , during the Revolution, fora ‘ ‘in is jn or „ r 1 °! n . “ells, was contrived by Fourcrov; founded upon the chemical facther" A eertahimuw-f an , d “^'zable ‘ban copper. '

atory furnace ■ in " 0 , bell-metal was completely oxydized by calcination in a rever-• Into the same r ox I de was raked out, and reduced to a fine powder.

urnace a fresh quantity of the same metal was introduced; it was