The alloy with 12% of silicon is white, hard and brittle.
The eutectic alloy itself, fig.
Sometimes the whole alloy is a uniform solid solution.
The term "alloy" does not necessarily imply obedience to the laws of definite and multiple proportion or even uniformity throughout the material; but some alloys are homogeneous and some are chemical compounds.
Subsequently electrum (an alloy of gold and silver) disappeared as a specific metal, and tin was ascribed to Jupiter instead, the sign of mercury becoming common to the metal and the planet.
An alloy of 15 parts of bismuth, 8 of lead, 4 of tin and 3 of cadmium (Wood's alloy) melts below 70° C.
It was, however, found that the behaviour of this alloy was in part due to a layer of pure iron (" ferrite ") averaging o 1 mm.
The original top stratum is the purest, and each succeeding lower stratum has a greater proportion of impurities; the lowest consists largely of a solid or semi-solid alloy of tin and iron.
It is certain that the structure existing in the alloy is closely connected with the mechanical properties, such as hardness, toughness, rigidity, and so on, that make particular alloys valuable in the arts, and many efforts have been made to trace this connexion.
According to one story, Archimedes was puzzled till one day, as he was stepping into a bath and observed the water running over, it occurred to him that the excess of bulk occasioned by the introduction of alloy could be measured by putting the crown and an equal weight of gold separately into a vessel filled with water, and observing the difference of overflow.
Ruthenium in bulk resembles platinum in its general appearance, and has been obtained crystalline by heating an alloy of ruthenium and tin in a current of hydrochloric acid gas.
The Romans used it largely, as it is still used, for the making of water pipes, and soldered these with an alloy of lead and tin.
In 1842 Karsten discovered that lead could be desilverized by means of zinc. His invention, however, only took practical form in1850-1852through the researches of Parkes, who showed how the zinc-silver-lead alloy formed could be worked and the desilverized lead freed from the zinc it had taken up. In the Parkes process only 5% of the original lead need be cupelled.
In large works the silver-lead alloy is removed when it contains 60-80 silver, and the cupellation of the rich bullion from several concentration furnaces is finished in a second furnace.
As this complete desilverization is only possible by the use of an excess of zinc, the unsaturated zinc-silver-lead alloy is put aside to form part of the second zincking of the next following charge.
An alloy made by addition of about 6th of arsenic has been used for making shot.
Tin unites with lead in any proportion with slight expansion, the alloy fusing at a lower temperature than either component.
"Pewter" (q.v.) may be said to be substantially an alloy of the same two metals, but small quantities of copper, antimony and zinc are frequently added.
Heusler that an alloy consisting of copper, aluminium and manganese (Heusler's alloy), possesses magnetic qualities comparable with those of iron.
Guillaume' the temperature at which the magnetic susceptibility of nickel-steel is recovered is lowered by the presence of chromium; a certain alloy containing chromium was not rendered magnetic even by immersion in liquid air.
Thus in an alloy containing 26.5% of manganese and 14.6% of aluminium, the rest being copper, the induction for H= 20 was 4500, and for H=150, 5550.
Guillaume 6 explains the ferromagnetism of Heusler's alloy by supposing that the naturally low critical temperature of the manganese contained in it is greatly raised by the admixture of another appropriate metal, such as aluminium or tin; thus the alloy as a whole becomes magnetizable at the ordinary temperature.
Hadfield 7 have made very careful experiments on an alloy containing 22.42% of manganese, 11.65% of ' J.
From the alloy containing 25% of silicon, the excess of magnesium is removed by a mixture of ethyl iodide and ether and a residue consisting of slate-blue octahedral crystals of magnesium silicide is left.
What is known as cast iron is essentially an alloy of iron proper with 2 to 6% of carbon and more or less of silicon.
It consists of a stoneware tank with a thin sheet of platinum-iridium alloy at either end forming the primary electrodes, and between them a number of glass plates reaching nearly to the bottom, each having a platinum gauze sheet on either side; the two sheets belonging to each plate are in metallic connexion, but insulated from all the others, and form intermediary or bi-polar electrodes.
But it is not permissible to call brass a chemical compound, for we can largely alter its percentage composition without the substance losing the properties characteristic of brass; the properties change more or less continuously, the colour, for example, becoming redder with decrease in the percentage of zinc, and a paler yellow when there is more zinc. The possibility of continuously varying the percentage composition suggests analogy between an alloy and a solution, and A.
The majority of alloys, when examined thus, prove to be complexes of two or more materials, and the patterns showing the distribution of these materials throughout the alloy are of a most varied character.
Successful; for example, in the case of steel, which is an alloy of iron and carbon, a microscopical examination gives valuable information concerning the suitability of a sample of steel for special purposes.
Mixture by fusion is the general method of producing an alloy, but it is not the only method possible.
Thus a strip of zinc plunged into a solution of silver sulphate, containing not more than 0.03 gramme of silver in the litre, becomes covered with a flocculent precipitate which is a true alloy of silver and zinc, and in the same way, when copper is precipitated from its sulphate by zinc, the alloy formed is brass.
Spring has shown that by compressing a finely divided mixture of i 5 parts of bismuth, 8 parts of lead, 4 parts of tin and 3 parts of cadmium, an alloy is pro duced which melts at ioo C., that is, much below the meltingpoint of any of the four metals.
In the case of this pair of metals, or indeed of any metallic alloy, we cannot see the crystals forming, nor can we easily filter them off and examine them apart from the liquid, although this has been done in a few cases.
Osmond, shows the structure of a silver-copper alloy containing considerably Eutectic more silver than the eutectic.
If we melt an alloy and chill it before it has wholly solidified, we often get evidence of the crystalline character of the solid matter which first forms. Fig.
This alloy, if allowed to solidify completely before chilling, turns into a uniform solid solution, and at still lower temperatures the solid solution breaks up into a pearlite complex.
Whence the Egyptians and a little later on the Babylonians got their tin for the alloy we do not yet know.
An alloy of 5 of lead, 8 of bismuth and 3 of tin fuses at 94.4° C., i.e.
The "tin" of the Bible (KauoLTEpos in the Septuagint) corresponds to the Hebrew bedhil, which is really a copper alloy known as early as 1600 B.C. in Egypt.
Such an alloy can be cast like ordinary bronze, but excels the latter in hardness, elasticity, toughness and tensile strength.
He weighed out a lump of gold and of silver of the same weight as the crown; and, immersing the three in succession in water, he found they spilt over measures of water in the ratio:: A or 33: 24: 44; thence it follows that the gold: silver alloy of the crown was as I I: 9 by weight.
Aluminium bronze (aluminium and copper) and ferro-aluminium (aluminium and iron) have been made in this way; the latter is the more satisfactory product, because a certain proportion of carbon is expected in an alloy of this character, as in ferromanganese and cast iron, and its presence is not objectionable.
The reduced aluminium alloys itself immediately with the fused globules of metal in its midst, and as the charge becomes reduced the globules of alloy unite until, in the end, they are run out of the tap-hole after the current has been diverted to another furnace.
Glass stills heated by a sand bath are sometimes employed in the final distillation of sulphuric acid; platinum, and an alloy of platinum and iridium with a lining of gold rolled on (a discovery due to Heraeus), are used for the same purpose.
Bronze is called by the Japanese kara-kane, a term signifying Chinese metal and showing clearly the source from which knowledge of the alloy was obtained.
It is almost impossible by mechanical means to detect the separate ingredients in such an alloy; we may cut or file or polish it without discovering any lack of homogeneousness.
Regarded as descriptive of the genesis of an alloy from a uniform liquid containing two or more metals, the term is not incorrect, and it may have acted as a signpost towards profitable methods of research.
We can sometimes obtain definite compounds in a pure state by the action of appropriate solvents which dissolve the rest of the alloy and do not attack the crystals of the compound.
Much information as to the nature of an alloy can be obtained by placing several small ingots of the same alloy in a furnace which is above the melting-point of the alloy, and allowing the temperature to fall slowly and uniformly.
The graphical representation of the properties of alloys can be extended so as to record all the changes, thermal and chemical, which the alloy undergoes after, as well as before, solidification, including the formation and breaking up of solid solutions and compounds.
8) be an equilateral triangle, the angular points corresponding to the three pure metals A, B, C. C Then the composition of any alloy can be FIG.
I live in the angle of a leaden wall, into whose composition was poured a little alloy of bell-metal.
Tin, bismuth) to give the alloy certain properties.
Various nickel-steels all expanded under magnetization, the increase being generally considerable and proportional to the field; in the case of an alloy containing 29% of nickel the change was nearly 40 times greater than in soft iron.
Richard Chevenix (1774-1830), a chemist, having bought some of the substance, decided after experiment that it was not a simple body as claimed, but an alloy of mercury with platinum, and in 1803 presented a paper to the Royal Society setting forth this view.
For example, the compound Cu3Sn is not indicated in the freezing-point curve, and indeed a liquid alloy of this percentage does not begin to solidify by the formation of crystals of Cu 3 Sn; the liquid solidifies completely to a uniform solid solution, and only at a lower temperature does this change into crystals of the compound, the transformation being accompanied by a considerable evolution of heat.
But modern work has shown that, although alloys sometimes contain solid solutions, the solid alloy as a whole is often far more like a conglomerate rock than a uniform solution.
We see however the similarity of the metal-working of both countries at approximately the same time; both are in the same style of artistic development, the Egyptian perhaps the more advanced of the two, and (if the published analysis by Mosso is to be relied upon) with the additional technique of the alloy with tin, making the metal bronze, and so easier for the heads to be cast.
An alloy containing about 3 parts of iron and I of nickel - both strongly magnetic metals - is under ordinary conditions practically non-magnetizable (1 1=1'4 for any value of H).
But if the alloy is heated up to 580° C. it loses its susceptibility - rather suddenly when H is weak, more gradually when H is strong - and remains non-magnetizable till it is once more cooled down below the freezing-point.