Sometimes the whole alloy is a uniform solid solution.
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.
If the lead is therefore rightly proportioned to the standard of alloy, the resulting button will consist of only gold and silver, and these are separated by the operation of parting, which consists in boiling the alloy (after rolling it to a thin plate) in strong nitric acid, which dissolves the silver and leaves the gold as a coherent sponge.
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.
The alloys of tin and gold are hard and brittle, and the combination of the metals is attended with contraction; thus the alloy SnAu has a density 14.243, instead of 14.828 indicated by calculation.
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 extent to which the properties of silver are modified by addition of copper depends on the fineness of the alloy produced.
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.
It may be prepared from osmiridium by fusing the alloy with zinc, the zinc being afterwards removed by distillation.
Tin unites with lead in any proportion with slight expansion, the alloy fusing at a lower temperature than either component.