The advantage of jewelry made from gold alloys, silver, platinum, palladium, determined by the breakdown, ie, the number contained in these alloys of precious metals. If, for example, gold jewelry has a stamp with the number 583, it means that the decoration Made of alloy, 1000, parts of which (by mass) consists of 583 pieces of gold and 417 parts of other metals. The higher the sample, the more precious metals contained in a particular decoration.
In Britain and the U.S. not adopted the metric, and carat system tests. Carat – a unit mass of precious stones, equal to 200 mg. Under this system, the metric assay with a value of 1000 corresponds to 24 carat. To convert one sample to another use ratio 24/1000 = x / y, where x – carat sample, and a – metric. Solving this relation, we find that a= 1000s/ 24, which means that, for example, the sample of 750 corresponds to the 18-carat sample, the sample of 583 – 14-carat, the sample of 500 – 12-carat, Sample 375 – 9 – carat, and 333 sample – 8-carat.
There are several methods for the determination of samples of precious metals and their alloys. These include the Testing of the assay on a stone (chert), Cupellation in a muffle furnace, chemical-analytical methods. The easiest way – drop, consisting of drawing on test articles of gold chloride solution or potassium dichromate, silver nitrate, potassium iodide or zhelezistosinerodistogo.
The most common assay for Testing of stone. Determination of samples of precious metals by this method is as follows. The surface of the assay of stone, natural or synthetic (preferably natural), lightly grease with almond, walnut, cedar or other vegetable oil, then wipe dry. After this alloy, samples of which shall be determined, and the assay needle (standard with a known gold content) on stone surfaces rub strips on the same force of pressing density. The appropriate reagent strips are moistened (across). After a 20-30 with a reagent carefully dried, removing excess filter paper, and compare its effect on strips left the subject alloy and assay needle. The gold content in the alloy is determined by the color intensity of spots formed by the action of the reagent on the strips: the more intense color of stain, the less gold in the alloy. A bright spot confirms the higher fineness, the same color stain on the strips of the alloy and the needle indicates the coincidence of their samples.