Testing Silver Wares.
Take nitric acid, six ounces; water, two ounces; bichromate of potash, one ounce. Reduce the salt of potash to a powder and well mix it with the acid and water. The solution is used cold, and should be placed in a stoppered glass bottle, the stopper having a long dropper extending into the mixture, which acts as the agent for conveying the liquid from the bottle to the article to be tested. The surface of the article should be perfectly clean, and to make certain what kind of metallic substance you are testing, it is advisable to rub a file over some obscure part of the surface and to apply the liquid to that part. The test liquid should be used, by means of the glass stopper, to the filed part, and immediately removed by a sponge damped with cold water. If the article consists of pure silver, there will appear a clean blood-red mark, which is less deep and lively in proportion to the quality of the metal. Upon platinum the test liquid has no action whatever; on German silver at first a brown mark appears, but this is removed by the sponge and cold water; on Britannia metal a black mark is produced; and on all the various metals an entirely different result takes place to that on silver; therefore the test is a simple one, and may be advantageously employed for the detection of any fraud in relation to the precious metal.
Another Test.
Water, 2 oz.; sulphuric acid, 2 drs.; chromate of potash, 4 dwts. This mixture is applied in the same way as before and produces a purple colour of various depths, according to the quality of the silver. No other metallic element exhibits the same colour with this preparation.
Perchloride of Iron.
Take spirits of salts, 8 oz.; crocus powder (jeweller’s polishing material), 1 oz.; well mix them together and keep in solution. In preparing the mixture for the dissolution of soft solder, &c., take 1 oz. of it, and add to it 4 ozs. of boiling water.
Aluminium Alloy.
Copper, 18 dwts; aluminium, 2 dwts.
New Alloy.