Metals copper and gold are externally very similar at each other. It is from each other rather easy to distinguish them if to use different physical or chemical properties of these elements. In the first case it is necessary to determine metal density, in the second – to be guided on reaction of the studied substance with some chemical reactants. Density of pure gold is 19.30 g/cm3, and copper - 8.93 g/cm3. Gold is quite inert metal, it is bad, unlike copper, reacts with mineral acids.
It is required to you
- laboratory measuring capacity, pharmaceutical lever scales, set of weights, lyapisny pencil, assay stone, jewelry reactant. The jewelry reactant consists of solution of bichromate of potassium, the concentrated sulfuric acid of dichloride copper in the distilled water in the ratio 10:6:5:79 (in grams).
Instruction
1. Gather in the measuring capacity of water. Measure level on a scale on a capacity wall. Put the studied metal in this capacity. Once again measure water level in capacity. Calculate metal volume, having taken away result of the first measurement from result of the second measurement of water level in capacity.
2. Weigh the studied metal, having put it on one cup of pharmaceutical scales. Achieve full equilibration of scales. For this purpose consistently in various combinations put weights on other cup of these scales. Count the total size of weight of the weights lying on balanced scales. It will be the weight of the checked metal.
3. For calculation of size of density and definition of substance of metal divide its weight into volume, then compare the received density to reference values of density of metals. This method can be used for definition of substance of metals with the low level of impurity.
4. For determination of amount of the main substance in metal alloy (up to 40%) use a lyapisny pencil. Rub the surface of metal with a lyapisny pencil. If the amount of gold in alloy is less than 40%, its surface will darken.
5. For the better analysis of alloy use a jewelry reactant. Apply samples of the studied metal on an assay stone. Drip on samples several drops of a reactant. In 20 seconds determine approximate structure by color of samples of metal on an assay stone. If color changed on dark brown, it gold alloy 375 of test means, brownish brown - the 500th test, light brown - the 585th test, and light yellow means test alloy 750.