GOLD 697 



slightest quantity of greasy matter will tarnish and render useless, until re-distillation, 

 a largo quantity of quicksilver. 



In 1865, Mr. W. Crookes, F.R.S. the discoverer of thallium, proposed to remedy 

 the evils attendant on the trituration of sulphides and arsenides in quicksilver by the 

 introduction of sodium. 



In laboratory-experiments the effects of Mr. Crookes' discovery were very con- 

 spicuous : 



1. A small quantity of sodium-amalgam added to ordinary quicksilver greatly in- 

 creased its brightness and affinity for gold. 



2. A bar of gold completely covered with tallow dipped into quicksilver containing 

 sodium was instantly amalgamated. 



3. Greasy (' sickened ') quicksilver was instantly made bright and clear by the ad- 

 dition of the sodiiim -amalgam. 



4. ' Floured ' quicksilver immediately collected on the introduction of a small quan- 

 tity of the sodium-amalgam. 



These novel facts induced Mr. Readwin to put the invention to a crucial test, 

 at the Gwynfynydd mine. He thus writes : ' I have made a series of experimental 

 trials, which have given me some confidence in the utility of Mr. Crookes' invention. 

 I selected for trial such auriferous minerals from Cwmheisian, Tyddynglwadis, North 

 Dolfrwynog, Gwynfynydd, Glasdir, and other places, that have always heretofore 

 either sickened the quicksilver, or refused to give up, by amalgamation, the gold 

 known to be contained in them by analysis. In no one instance, during these 

 experiments (some of which were of 48 hours' duration), did I derange the quick- 

 silver in operation, and in every instance I obtained gold from it, on distillation. 

 The quantities of gold, of course, varied with the samples of minerals treated, and 

 did not in any way affect the value of the experiments, the object of which was 

 chiefly to prove whether heterogeneous minerals could be treated by this method, 

 when they would not submit to other tried methods. The most remarkable, and in 

 my opinion the most important, effect of the sodium, was seen in an experiment on 

 56 Ibs. of mixed minerals from one of the Gwynfynydd lodes. The gold in this lode 

 is often visible and associated with sulphides of lead, zinc, and arsenic. Quicksilver 

 'n its ordinary state was first used in this experiment, which shortly became com- 

 'letely ' sickened ' by yellow sulphide of arsenic (orpiment), and completely coated 

 he ' Britten ' machine with arsenic-amalgam. Whilst in this state, sodium-amalgam 

 of about 3 per cent, strength was introduced ; the quicksilver soon recovered its 

 fluidity, became quite bright and clear, and on distillation yielded nearly two ounces 

 of gold. I made many other experiments, and in practice I found that, although I 

 was always able to obtain gold by the use of sodium when I could not obtain it 

 otherwise, I discovered that an excess of sodium predisposed the quicksilver to take 

 up other metals, to the partial exclusion of the one most particularly desired ; but in 

 all cases the quicksilver was kept quite bright and clear, and on washing out the 

 machines, the subdivided particles were most rapidly re-united, a circumstance of itself 

 of the greatest importance. 1 



Mr. Readwin believes that native lead exists to a considerable extent in some of the 

 minerals, and he shows that the prevalence of galena, &c., is the greatest hindrance 

 in amalgamation. If this be so, and the lead can be taken out of the concentrated 

 ores before amalgamation without losing the gold and silver, the plan may possibly 

 render amalgamation of the residue practicable. Mr. Peter Spence, of Manchester, 

 proposed to calcine the sulphides containing galena till completely oxidised ; a portion 

 of the galena is thus converted into sulphate of lead, and a portion into oxide of lead. 

 This oxide and sulphate of lead is then washed in a solution of carbonate of soda, 

 and the sulphate is converted into a carbonate. The calcined ore is then put into a 

 solution of caustic alkali, the mixture is stirred for a short time, the solution taken 

 off, and more solution added whilst the oxide of lead remains ; the various solutions 

 added together are allowed to settle, and, when perfectly clear, drawn off into a vessel 

 into which carbonic acid can be thrown into the solution and absorbed by it ; as the 

 carbonic acid becomes absorbed by the solution, the soda becomes carbonated, and 

 white lead is deposited. 



Mr. Spence undoubtedly can convert the sulphide into carbonate of lead, as he 

 proposes, but the process has not in any way affected the value of auriferous and 

 argentiferous minerals. Mr. Spence asserts positively that by his process the lead 

 in any ores can be converted into white lead, leaving the residual and accidental 

 products for _ after-treatment, according to their nature and value, and this in a rapid 

 and inexpensive manner. 



1 Since the above experiments were tried Mr. Crookes has improved his process, and thus avoids 

 the ill effects of an excess of sodium ; the improvements met the approval of Dr. W. Allen Miller 

 and other high authorities. 



