August 17, 1905] 



NA TURE 



379 



alluding to were it not for the fact that we are to-day 

 meeting on the Rand where the infant process made its 

 debut nearly fourteen years ago. The Rand to-day is the 

 richest of the world's goldfields, not only in its present 

 capacity, but in its potentialities for the future ; twenty 

 years ago its wonderful possibilities were quite unsuspected 

 even by experts. 



It is not for me to describe in detail how the change 

 has been accomplished ; this task will, we know, be far 

 better accomplished by representative chemists who are 

 now actively engaged in the work. But for the chemists 

 of the British Association it is a fact of great significance 

 that they are here in the presence of the most truly in- 

 dustrial development of gold production which the world 

 has yet seen ; a development moreover that is founded on 

 a purely chemical process which for its continuance re- 

 quires, not only skilled chemists to superintend its oper- 

 ation, but equally skilled chemists to supply the reagent 

 on which the industry depends. 



In 18S9 the world's consumption of cyanide of potassium 

 did not exceed fifty tons per annum. This was produced 

 by melting ferrocyanide with carbonate of potassium, the 

 clear fused cyanide so obtained being decanted from the 

 carbide of iron which had separated. The resulting salt 

 was a mixture of cyanide, cyanate, and carbonate which 

 was sometimes called cyanide of potassium for the hardly 

 sufficient reason that it contained 30 per cent, of that 

 salt. When the demand for gold extraction arose, it was 

 at first entirely met by this process, the requisite ferro- 

 cyanide being obtained by the old fusion process from 

 the nitrogen of horns, leather, &c. In 1891 the first 

 successful process for the synthetic production of cyanide 

 without the intervention of ferrocyanide was perfected, 

 and the increasing demand from the gold mines was largely 

 met by its use. At present the entire consumption of 

 cyanide is not much short of 10,000 tons a year, of which 

 the Transvaal goldfield consumes about one-third. Large 

 cyanide works exist in Great Britain, Germany, France, 

 and America, so that a steady and sure supply of the 

 reagent has been amply provided. In 1894 the price of 

 cyanFde in the Transvaal was 2s. per pound ; to-day it is 

 one-third of that, or 8d. During the prevalence of the 

 high prices of earlier years the manufacture was a highly 

 speculative one, and new processes appeared and dis- 

 appeared with surprising suddenness, the disappearance 

 being generally marked by the simultaneous vanishing 

 of large sums of money. To-day the manufacture is 

 entirely carried out in large works scientifically organised 

 and supervised, and, both industrially and commercially, 

 the speculative element has been eliminated. 



Chemistry has so often been called on to play the pari 

 of the humble and unrecognised handmaiden to the in- 

 dustrial arts that we may perhaps be pardoned if in this 

 case we direct public attention to our Cinderella as she 

 shines in her rightful position as the genius of industrial 

 initiation and direction. 



To this essentiallv chemical development of metallurgy 

 we owe it that in a community the age of which can only 

 be counted by decades we find ourselves surrounded by 

 chemists of high scientific skill and attainments who have 

 already organised for their mutual aid and scientific 

 enlightenment " The Johannesburg Society of Chemistry, 

 Metallurgy, and Mining," the published proceedings of 

 which amply testify to the atmosphere of intellectual 

 vigour in which tbe work of this great industry is 

 carried on. 



It appears, then, that while gold still maintains ■ its 

 position of influence in the affairs of men, the nature of 

 that influence has undergone an important change. Not 

 onlv has its widespread use as the chief medium of ex- 

 change exercised far-reaching effects on the commerce of 

 the world, but the vastly increased demand for this purpose 

 has in its turn altered the methods of production. These 

 methods have become more highly organised and scientific, 

 and gold production is now fairly established as a pro- 

 gressive industry in which scope is found for the best 

 chemical and engineering skill and talent. 



The experience of more highly evolved industries in the 

 older countries has shown that the truly scientific organ- 

 isation of industry includes in its scope a full and just 

 consideration for the social and intellectual needs of its 



NO. i868, VOL. 72] 



workers from highest to lowest. It augurs well, therefore, 

 for the future of the gold industry, from the humane and 

 social points of view, that its control should be more and 

 more under the influence of men of scientific spirit and 

 intellectual culture who we may feel assured will not 

 forget the best traditions of their class. 



The application of science to industry requires on the 

 part of the pioneers and organisers keen and persistent 

 concentration on certain well-defined aims. Any waver- 

 ing in these aims or any relaxation of this concentration 

 may lead to failure or to only a qualified success. This 

 necessary but narrow concentration may be a danger to 

 the intellectual development of the worker, who may 

 thereby readily fall into a groove and so may become 

 even less efficient in his own particular work. It 

 certainly requires some mental strength to hold fast to 

 the well-defined practical aim while allowing to the atten- 

 tion occasional intervals of liberty to browse over the 

 wide and pleasant fields of science. But I am certain 

 that the acquirement of this double power is well worth 

 an effort. The mental stimulus, as well as the new ex- 

 periences garnered during the excursion, will sooner or 

 later react favourably on the practical problems, while 

 the earnest wrestling with these problems may develop 

 powers and intuitions which will lend their own charm 

 to the wider problems of science. 



Gold and Science. 



If we re-peruse the table of the elements, not now in 

 our capacity as " plain men " but as chemists, we shall 

 certainly not select gold as of supreme interest chemically. 

 Its position as chief among the noble metals, its patent 

 of nobility, is based on its aloofness from common associ- 

 ations or attachments. Unlike the element nitrogen, it 

 is mainly for itself and little if at ail for its compounds, 

 that gold is interesting. In it we can at our leisure study 

 the metal rather than the element. Its colour and trans- 

 parence, its softness and its hardness, the density as well 

 as the extreme tenuity of some of its forms — such were 

 the qualities which recommended it to Faraday when he 

 desired to study the action of material particles on light. 

 I should like to repeat to you in his own words the reasons 

 he gave for this choice : " Because of its comparative 

 opacity among bodies, and yet possession of a real trans- 

 parency ; because of its development of colour both in the 

 reflected and transmitted rays ; because of the state of 

 tenuity and division which it permitted with the preserv- 

 ation of its integrity as a metallic body ; because of its 

 supposed simplicity of character ; and because known 

 phenomena appeared to indicate that a mere variation 

 in the size of its particles gave rise to a variety of re- 

 sultant colours. Besides the waves of light are so large 

 compared to the dimensions of the particles of gold which 

 in various conditions can be subjected to a ray, that it 

 seemed probable that the particles might come into effective 

 relations to the much smaller vibrations of the other 

 particles." 



I may remind you that Faraday came to the conclusion 

 that the variety in the colours presented by gold under 

 various conditions is due to the size of its particles and 

 their state of aggregation. Ruby glass or ruby solutions 

 he proved are not true solutions, nor are they molecular 

 diffusions of gold, but they contain the metal in aggregates 

 sufficiently large to give a sensible reflection under an 

 incident beam of light. Through the kindness of Sir 

 Henry Roscoe I am able to exhibit to you some of the 

 original ruby gold preparations obtained during this re- 

 search, which were afterwards presented to him by Fara- 

 day at' the Royal Institution some years before his death. 



By means of refined and ingenious optical _ methods 

 Zsigmondy and Siedentopf have succeeded in making these 

 ultrli-microscopic particles visible in the microscope as 

 diffraction discs ; they have, further, counted the number 

 of particles per unit area, and have from the intensity of 

 their reflection calculated their size. In ruby glass the 

 size of the particles in different specimens was found to 

 vary from 4 to 791 millionths of a millimetre. No re- 

 lation was found to hold between the colour of the particles 

 and their absolute size. This conclusion is in direct con- 

 tradiction of Faraday's belief already referred to. Mr. 

 J. Maxwell Garnett has recently shown that the colour 



