378 



NA TURE 



[August 17, 1905 



divergence and in spite of scattered isolation, the sum 

 of human knowledge, which is an inheritance common to 

 us all, grows silently, sometimes slowly, yet (as we hope) 

 safely and surely, through the ages. You who are in 

 South Africa have made an honourable and an honoured 

 contribution to that growing knowledge, conspicuously in 

 your astronomy and through a brilliant succession of 

 astronomers. Here, not as an individual but as a re- 

 presentative officer of our brotherhood in the British 

 Association, I can offer you no better wish than that you 

 may produce some men of genius and a multitude of able 

 workers who, by their researches in our sciences, may 

 add to the fame of your country and will contribute to the 

 intellectual progress of the world. 



SECTION B. 



chemistry. 



Ope.mng Address by G. T. Beilby, President of the 



Section. 

 In scanning the list of the elements with which we are 

 thoughtfully supplied every year by the International Com- 

 mittee on Atomic Weights, the direction in which our 

 thoughts are led will depend on the particular aspect of 

 chemical study which happens to interest us at the time. 

 Putting from our minds on the present occasion the 

 attractive speculations on atomic constitution and dis- 

 integration with which we have all become at least super- 

 ficially familiar during the past few years, let us try to 

 scan this list from the point of view of the " plain man " 

 rather than from that of the expert chemist. Even a 

 rudimentary knowledge will be sufficient to enable our 

 " plain man " to divide the elements broadly into two 

 groups — the actually useful and the doubtrully useful or 

 useless. Without going into detail we may take it that 

 about two-thirds would be admitted into the first group, 

 and one-third into the second. It must, I think, be re- 

 garded as a very remarkable fact that of the eighty 

 elements which have had the intrinsic stability to enable 

 them to survive the prodigious forces which must have been 

 concerned in the evolution of the physical universe, so 

 large a proportion are endowed with characteristic proper- 

 ties which could ill have been spared either from the 

 laboratories of Nature or from those of the Arts and 

 Sciences. Even if one-third of the elements are to be 

 regarded as waste products or failures, there is here no 

 counterpart to the reckless prodigality of Nature in the 

 processes of organic evolution. 



If we exclude those elements which participate directly 

 and indirectly in the structure and functions of the organic 

 world, there are two elements which stand out con- 

 spicuously because of the supreme influence they have 

 exercised over the trend of human effort and ambition. 

 I refer, of course, to the metals gold and iron. 



From the early beginnings of civilisation gold has been 

 highlv prized and eagerly sought after. Human life has 

 been freely sacrificed in its acquirement from natural 

 sources, as well as in its forcible seizure from those who 

 alreadv possessed it. The " .^ge of Gold " was not neces- 

 sarily '" The Golden Age," for the noble metal in its 

 unique and barbaric splendour has symbolised much that 

 has been unworthy in national and individual aims and 

 ideals. 



We have accustomed ourselves to think of the present 

 as the Age of Iron, as indeed it is, for we see in the dull, 

 grey metal the plastic medium out of which the engineer 

 has modelled the machines and structures which play so 

 large a part in the active life of to-day. Had iron not 

 been at once plentiful and cheap, had it not brought into 

 the hands of the engineer and artificer its marvellous 

 qualities of hardness and softness, of rigidity and tough- 

 ness, and to the electrician its mysterious and unique 

 magnetic qualities, it is not difficult to conceive that man's 

 control over the forces of Nature might have been delayed 

 for centuries, or perhaps for ages. For iron has been 

 man's chief material instrument in the conquest of Nature; 

 without it the energy alike of the waterfall and of the 

 roalfield would h.-'ve remained uncontrolled and unused. 

 In this conquest of the resources of Nature for the service 

 of man are we not entitled to say that the intellectual 



NO. I Sf'S, voT.. 72] 



and social gains hare equalled, if they have not exceeded, 

 in value the purely material gains ; and may we not then 

 regard iron as the symbol of a beneficent conquest of 

 Nature? 



With the advent of the Industrial Age gold was destined 

 to take a new place in the world's history as the great 

 medium of exchange, the great promoter of industry and 

 commerce. While individual gain still remained the pro- 

 pelling power towards its discovery and acquisition, every 

 fresh discovery led directly or indirectly to the freer inter- 

 change of the products of industry, and thus reacted favour- 

 ably on the industrial and social conditions of the time. 



So long as the chief supplies of gold were obtained 

 from alluvial deposits by the simple process of washing, 

 the winning of gold almost necessarily continued to be 

 pursued by individuals, or by small groups of workers, 

 who were mainly attracted by the highly speculative nature 

 of the occupation. These workers endured the greatest 

 hardships and ran the most serious personal risks, drawn 

 on from dav to day by the hope that some special stroke 

 of good fortune would' be theirs. This condition prevailed 

 also in fields in which the reef gold occurred near the 

 surface, where it was easily accessible without costly 

 mining appliances, and where the precious metal was 

 looselv associated with a weathered matrix. These free- 

 milling ores could be readily handled by crushing and 

 amalgamation with mercury, so that here also no elaborate 

 organisation and no great expenditure of capital were 

 necessary. .A third stage was reached- when the more 

 easily worked deposits above the water-line had been 

 worked out. Not only were more costly appliances and 

 more elaborately organised efforts required to bring the 

 ore to the surface, but the ore when obtained contained 

 less of its gold in the easily recovered, and more in the 

 refractory or combined form. The problem of recovery 

 had now to be attacked by improved mechanical and 

 chemical methods. The sulphides or tellurides with which 

 the gold was associated or combined had to be reduced to 

 a state of minute subdivision by more perfect stamping 

 or grinding, and elaborate precautions were necessary to 

 ensure metallic contact between the particles of gold and 

 the solvent mercury. In many cases the amalgamation 

 process failed to extract more than a very moderate pro- 

 portion of the gold, and the quartz sand or " tailings " 

 which still contained the remainder found its way into 

 creeks and rivers or remained in heaps on the ground 

 around the batteries. In neighbourhoods where fuel was 

 available a preliminary roasting of the ore was resorted 

 to, to oxidise or volatilise the baser metals and set free 

 the gold ; or the sulphides, tellurides, &c., were concen- 

 trated by washing, and the concentrates were taken to 

 smelting or chlorinating works in some favourable situ- 

 ation where the more elaborate metallurgical methods 

 could be economically applied. Many efforts were also 

 made to apply the solvent action of chlorine directly to 

 the unconcentrated unroasted ores ; but unfortunately 

 chlorine is an excellent solvent for other substances besides 

 gold, and in practice it was found that its solvent energy 

 was mainly exercised on the base metals and metalloids, 

 and on the materials of which the apparatus itself was 

 constructed. 



This to the best of my knowledge is a correct, if rather 

 sketchv, description of the state of matters in 1889 when 

 the use of a dilute solution of cyanide of potassium was 

 first seriously proposed for the extraction of gold from 

 its ores. Those of us who can recall the time will re- 

 member that the proposal was far from favourably re- 

 garded from a chemical point of view. The cost of the 

 reagent, its extremely poisonous nature, the instability 

 of its solutions, its slow action — such were the difficulties 

 that naturally presented themselves to our minds. .'\nd, 

 even granting that these difficulties might be overcome, 

 there still remained the serious problem of how to recover 

 the gold in metallic form from the extremely dilute solu- 

 tions of the cyanide of gold and potassium. How each 

 and all of these difficulties have been swept aside» how 

 within little more than a decade this method of gold 

 extraction has spread over the gold-producing countries 

 of the world, now absorbing and now replacing the older 

 processes, but ever carrving all before it — all this is already 

 a twice-told tale which 1 should feel hardly justified In 



