China.] 



ORIENTAL COMMERCE. 



487 



The metallic compositions made to resemble gold in colour, are readily 

 known by means of a drop or two of aqua-fortis, which has no effect upon 

 gold, but discharges the marks made by all its known imitations. That the 

 touchstone may be able to support this trial, it becomes a necessary charac- 

 ter of it not to be corrosible by acids, a character which shews it to be 

 essentially different from the marbles, whereof it is by many writers reckoned 

 a species. If gold is debased by an admixture of any considerable quantity 

 of these compositions, aqua-fortis wjjl in this case also discharge so much of 

 the mark as was made by the base metal, aud leave only that of the gold, 

 which will now appear discontinued, or in specks. Silver and copper are in 

 like manner eaten out from gold on the touchstone ; and hence some 

 judgment may thus be formed of the fineness of the metal, from die pro- 

 portion of the remaining gold to the vacuities. 



It has been observed that hard gold appears on the touchstone less fine 

 than it really is. It may be presumed that this difference does not proceed 

 from the simple hardness, but from the hardness being occasioned by an ad- 

 mixture of such metallic bodies as debase the colour in a greater degree than 

 an equal quantity of the common alloy. Silver and copper are the only 

 metals usually found mixed with gold, whether in bullion or in coins, 

 and the only ones whose quantity is attempted to be judged of by this 

 method of trial. 



The Chinese are extremely expert in the use of the touchstone, bo as to 

 distinguish by it so small a difference in the fineness as half a touch. It is 

 the only test by which they regulate the sale of their gold to Europeans, 

 and it is subject to fewer difficulties than in Eurojie, on account of the 

 uniformity of their alloy, which is almost always silver ; the least appearance 

 of copper being used in the alloy gives a suspicion of fraud. As an assay 

 of the gold is rarely permitted at China, it behoves the European trader to be 

 well practised in this way of examination. By carefully attending to the 

 fore^oino* directions, mid by accustoming himself to compare the colours of 

 a good set of touch-needles, having the fineness marked on each, it is pre- 

 sumed he will be able to avoid being imposed upon, either in the touch 

 itself, or by the abuses said to be sometimes committed, of covering the bar 

 or ingot with a thick coat of finer metal than the interior part, or of including 

 masses of base metal within it. A set of needles may be prepared for this 

 use with silver alloy in the series of the Chinese touches ; or the European 

 needles may be easily accommodated to the Chinese by the following Tables, 

 which reduce English carats into Chinese touches, and Chinese touches into 

 English carats, calculating 100 touch equal to 24 carats. 



