164 Mr. Hatchett's Experiments on the various Alloys , 
much more permanent, under all circumstances, than those of 
the fine gold. The difference of wear between the three kinds 
of standard gold abovementioned, does not in reality appear to 
be very considerable ; but, upon the whole, the preference may 
be given to gold alloyed with a mixture of silver and copper, or 
to that which has only copper for the alloy. 
4thly. That gold made standard partly by the addition of 
iron or tin, sustains a greater loss by friction than either of the 
three kinds of standard gold abovementioned. 
5thly. That gold reduced to 18 carats by copper, is more 
liable occasionally to wear, in a small degree, than the three 
kinds of standard gold which have been lately mentioned, pro- 
vided that the friction takes place between pieces of equal quality; 
but, in the contrary case, the principal loss always falls on the 
soft or standard gold, when it is opposed to gold of 18 carats, 
which is considerably harder. 
6thly. That gold more debased than that of 18 carats, such 
as gold alloyed with an equal proportion of copper, suffers very 
considerably more than any of the kinds hitherto mentioned, 
provided that the pieces are of the same quality ; but, on the 
contrary, fine and standard gold experience a very great loss, 
when exposed to the action of this debased gold, while the loss 
of the latter is comparatively much less. 
ythly. That the wear of standard silver appears to be nearly 
equal with that of fine gold ; but more than that of gold made 
standard by silver or by copper, and less than that of gold much 
debased by copper. 
8thly. That, as gold which is not inferior to standard wears 
in general less than standard silver, so does this last suffer much 
less than copper. 
