208 NOTICES OF THE MEETINGS [May 28, 
The sulphide of gold is converted into metal by the agency of heat 
alone.— A Council Medal was awarded for this process at the Great 
Exhibition of last year. In the first number of the Philosophical 
Magazine for 1848 will be found a series of experiments on this 
subject made by the Lecturer in 1847. r 
Melting of the Gold dust.—The gold obtained in grains (pepites) 
by washing, is melted in black lead crucibles with borax. The 
slag containing the foreign matter is skimmed off. A little 
corrosive sublimate is then, in particular cases, dropped in, after 
which the metal is cast into ingots. The use of corrosive sublimate 
is of ancient date. Some metallurgists believe its addition to be 
useless; but it is still occasionally employed by gold-melters of 
great experience. 
Parting or separation of the Silver.—This is effected either by 
nitric or sulphuric acid. Gold must be alloyed with from 23 to 3 
times its weight of silver to allow of the removal of the latter by the 
agency of either of those acids. The method of parting by nitric acid 
is well known. The process was briefly described. The silver dis- 
solved out from the gold is now generally precipitated from its solution 
in nitric acid as chloride, by the addition of common salt. The chlo- 
ride is washed and reduced to the metallic state by zinc.— Dr. Percy 
had intended to have given the results of careful experiments on the 
large scale, made by himself on the use of cast iron vessels in parting 
by sulphuric acid. The use of cast iron, for this purpose, was long 
ago proposed by a Frenchman at Marseilles. In the experiments 
just referred to, several thousands of ounces of silver were ope- 
rated on. No description has yet been published, so far as he is 
aware, giving all the practical details necessary to the successful 
application of iron vessels for parting. The shortness of the time 
prevented the fulfilment of the intention abovementioned. 
“In conclusion,” said Dr. Percy, “permit me to offer a few 
observations in connection with the subject which I have ventured to 
submit to the Members of the Royal Institution. That subject is 
essentially what is termed practical. Yet in every process which we 
have examined, the principles of science are involved. The metal- 
lurgic arts present a varied and beautiful field for investigation, and 
merit greater attention from chemists than they have yet received, 
at least in this country. The reactions which take place in many 
metallurgical operations require for their elucidation the highest 
science, and have only to be known to be duly appreciated. This 
evening I may speak freely of the attractions of metallurgy to the 
chemist, who is intent upon the investigation of the glorious truths of 
science for their own sake; but if I had to address Manufacturers 
upon the advantage of the applications of science to metallurgy I 
should be under the necessity of employing the only argument which 
will avail with them,— that of direct and positive advantage. 
“‘ We have seen, that although Gold may be present only in very 
