THE TECHNOLOGIST. [May 1, 1865. 



452 GOLD AND ITS ALLOYS. 



readily distinguish the pure metal from the alloy. Such an alloy is 

 scarcely affected by aquafortis unless below 14 carats. An alloy of 

 lead, even in minute proportion, say l-2000th, causes gold to be brittle ; 

 it has repeatedly occurred that the accidental mixture of two or three 

 shots in a parcel of gold dust has rendered it, when melted down and 

 cast into an ingot, incapable of being stamped without cracking. Some 

 other metals, as bismuth, antimony, &c, in a less degree produce a 

 similar effect. 



The crude gold of Victoria, though remarkably pure compared with 

 the produce of other countries, contains more or less silver. This 

 metal, together with a variable mixture of iron, stone, quartz, clay, and 

 other earthy matter, and in the case of the Ovens gold, tin ore, are the 

 usual impurities of our crude gold. 



In the operation of melting down, which is performed in crucibles 

 or melting-pots of the best quality that can be procured, with the aid of 

 fluxes, such as borax, soda, nitre, &c, all the earthy impurities, and in 

 part also the base metals, are separated. 



The ingot or bar of gold, which still retains the silver, resulting 

 from this operation will, of course, be less in actual weight than the 

 crude gold before melting ; but as the real waste of precious metal, 

 when the process is skilfully conducted, io trifling and unimportant, the 

 difference is referable to the separation of impurities only, and the im- 

 provement in quality and value is proportioned to the diminution in 

 quality. 



In the process of assaying, accurately weighed samples, usually 12 

 grains each, are taken from the different parts of the bar or ingot ; these 

 are submitted to two operations. 



First — Cupellatiou or melting with lead, by which all the base * 

 metals are separated. 



Secondly — Parting by nitric acid, by which the silver is removed, 

 leaving nothing but pure gold. [The details of these operations are 

 described in technical works on assaying.] 



The weight of the pure gold remaining after these operations being 

 accurately ascertained decides the fineness of the sample, but the 

 correctness of the assay is confirmed by the results of two or more 

 distinct assayers corresponding to within about l-32nd of a carat, or 

 l-7(35th of the whole weight of the sample. 



There are several ways in which the degree of fineness or purity of 

 gold is expressed in commerce. 



1st. Fiue gold is said to be 24 carats fine, and every carat is divided 

 iuto 32 parts. Thus, gold combined with an equal quantity of alloy 

 would be 12 carats fine. British standard gold, as used for coinage, is 



* Gold, silver, platiua. and some other rare metals, have been distinguished as 

 nolle, and copper, iron, and other metals, as base. In this instance, the term 

 noble is synonymous with fireproof. 



