The test
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By amalgamating gold with other metal the need has arisen to be able determine the gold quality of alloys.
The test is quick non-destructive, i.e. a not damaging method of research. Not only the quality of metal can be determined (quantitative research) but also the type of metal (qualitative research). For the test you need a touchstone, testneedles and test acids (mixture of acids and/or salts). A testneedle is a brass needle to which a gold alloy has been soldered, of which quality has been determined closely.
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The test goes as follows:
Scratch with the object on the touchstone so that there a considerable gold line lags behind. By putting a gold line with a testneedle beside this line you can stipulate, after the influence of a couple of drops acid on the touchstone, the quality. The testmethod is a method of research where especially experience and insight of the assayer is important. The method in itself is simple to learn but nevertheless it will take years to become a good assayer.
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Gold - and zilver quality are not expressed in percents (by hundred) but in promille (by thousand). Also gold quality is indicated in karates. 24 carats gold are 1000 thousandth in fine (i.e. pure) gold. 18 carats gold contains therefore 18/24 x 1000 = 750 thousandth of fine gold, 14 carats contain 14/24 x 1000 = 585 thousandth of fine gold and 8 carats contain 8/24 x1000 = 333 thousandth of fine gold.