NATURE 



[January 30, 1908 



" On this idea, in naming tlie bases of potash and soda, 

 it will be proper to adopt the termination which by common 

 consent has been applied to other newly discovered metals, 

 and which, though originally Latin, is now naturalised in 

 our language. 



" Potasium (sic) and sodium are the names by which I 

 have ventured to call the new substances ; and whatever 

 changes of theory, with regard to the composition of 

 bodies, may hereafter take place, these terms can scarcely 

 express an error ; for they may be considered as implying 

 simply the metals produced from potash and soda. I have 

 consulted with many of the most eminent scientific persons 

 in this country upon the methods of derivation, and the 

 one I have adopted has been the one most generally 

 approved. It is perhaps more significant than elegant. 

 But it was not possible to found names upon specific 

 properties not common to both ; and though a name for 

 the basis of soda might have been borrowed from the 

 Greek, yet an analogous one could not have been applied 

 to that of potash, for the ancients do not seem to have 

 distinguished between the two alkalies." 



Such, then, are the more significant features of one of the 

 greatest discoveries ever made by a British chemist, as 

 these are set forth in one of the most remarkable papers 

 in the Philosophical Transactions of the Royal Society. 



The publication of Davy's discovery created an extra- 

 ordinary sensation throughout the civilised world, a sensa- 

 tion not less profound, and certainly more general from its 

 very nature, than that which attended his lecture of the 

 previous year. But at the very moment of his triumph it 

 seemed that the noise of the universal acclaim with which 

 it was received was not to reach him. I have already 

 made reference to the condition of mental excitement under 

 which the discovery was made and prosecuted. Almost 

 immediately after the delivery of his lecture he collapsed, 

 struck down by an illness which nearly proved fatal, and 

 for weeks his life hung on a thread. He had been in a 

 low, feverish condition for some time previously, and 

 a great dread had fallen upon him that he should die 

 before he had completed his discoveries. It was in this 

 condition of body and mind that he had applied himself 

 to the task of putting together an account of his results. 

 Four days after this was given to the world he took to 

 his bed, and he remained there for nine weeks. Such a 

 blow following hard on the heels of such a triumph 

 aroused the liveliest sympathy. The doors of the Royal 

 Institution were beset by anxious inquirers, and written 

 reports of his condition at various periods of the day had 

 to be posted in the hall. The strength of the feeling may 

 be gleaned, too, from the sentences with which the Rev. 

 Dr. Dibdin, who had been hurriedly engaged to take his 

 place in the theatre, began the lecture introductory to the 

 session of 1808 : — ■ 



"The managers of this institution have requested me 

 to impart to you that intelligence, which no one who is 

 alive to the best feelings of human nature can hear with- 

 out the mixed emotion of sorrow and delight. 



Mr. Davy, whose frequent and powerful addresses 

 from this place, supported bv his ingenious experiments, 

 have been so long and so well known to you, has, for the 

 last five weeks, been struggling between life and death. 

 The effects of these experiments recently made in illustra- 

 tion of his late splendid discovery, added to consequent 

 bodily weakness, brought on a fever so violent as to 

 threaten the extinction of life. Over him it might 

 emohaticallv be said in the language of our immortal 

 Milton, that 



"... Dealh hi; Hart 

 Shook, but delayed to strike." 



If it had pleased Providence to deprive the world of 

 all further benefit from his original talents and intense 

 application, there has certainly been sufificient already 

 effected by him to entitle him to be classed among the 

 brightest scientific luminaries of his country." 



After having, " at the particular request of the 

 managers," given an outline of Davy's investigations. Dr. 

 Dibdin proceeded to say ; — 



" These may justly be placed among the most brilliant 

 and valuable discoveries which have ever been made in 

 chemistry, for a great chasm in the chemical system has 



NO. 1996, VOL. 7^] 



been filled up ; a blaze of light has been diffused over that 

 part which before was utterly dark ; and new views have 

 been opened, so numerous and interesting, that the more 

 any man who is versed in chemistry reflects on them, the 

 more he finds to admire and heighten his expectation of 

 future important results. 



" Mr. Davy's name, in consequence of these discoveries, 

 will Be always recorded in the annals of science amongst 

 those of the most illustrious philosophers of his time. His 

 country, with reason, will be proud of him, and it is no 

 small honour to the Royal Institution that these great dis- 

 coveries have been made within its walls — in that labora- 

 tory, and by those instruments which, from the zeal of 

 promoting useful knowledge, have, with so much propriety, 

 been placed at the disposal and for the use of its most 

 excellent professor of chemistry." 



And now, in the few minutes that remain to me, let 

 me indicate what has been the outcome of this great and 

 fundamental discovery. How far has the expectation of 

 future important results been realised? Have sodium and 

 potassium at all justified the hope that they would facili- 

 tate the means of procuring the comforts and conveniences 

 of life? 



I have not the time, even if I had the intention, to 

 attempt to follow the many changes in the metallurgy of 

 the metals of the alkalis of the past century. Let me at 

 once proceed to show how the matter stands at the end 

 of a hundred years. 



The general properties and chemical activities of 

 potassium and sodium are so very similar that, as a 

 matter of commercial production, that metal which can 

 be most economically obtained is necessarily the one most 

 largely manufactured, and of the two that metal is sodium. 

 To-day, sodium is made by thousands of tons, and by a 

 process which in principle is identical with that by which 

 it was first made by Davy, i.e. by the electrolysis of fused 

 caustic soda. It is very significant that after a series of 

 revolutions in its manufacture, sodium, having been pro- 

 duced from time to time on a manufacturing scale by a 

 variety of metallurgical methods involving purely thermal 

 processes of reduction and distillation, entirely dissociated 

 from electricity, we should have now got back to the very 

 principle of the process which first brought the metal to 

 light. And that this has been industrially possible is 

 entirely owing to another of Davy's discoveries — possibly 

 indeed the greatest of them all — Michael Faraday. As we 

 all gratefully acknowledge, it is to the genius and labours 

 of Faraday — Davy's successor in this place — that the 

 astonishing development of the application of electrical 

 energy which characterises this age has taken its rise. 



The modern method of production of sodium is based, 

 therefore, as regards principles, upon the conjoint labours 

 of Davy and Faraday. 



These principles took their present form of application at 

 the hands of a remarkably talented American — Mr. 

 Hamilton Y. Castncr — whose too early death, in the full 

 vigour of his intellectual powers, was an incalculable loss 

 to metallurgical chemistry. It is by Castner's process 

 that all the sodium of to-day is manufactured. 



In the Castner process melted caustic soda, produced by 

 the electrolysis of a solution of common salt by a method 

 also devised bv Castner, is brought into an iron vessel 

 shaped like a large cauldron, mounted in brickwork, and 

 provided with an extension adapted to receive the negative 

 electrode. .Suspended directly above the kathode is an iron 

 vessel attached to a lid ; to its lower edge is secured iron 

 wire gauze, which, when the receptacle is in position, 

 completely surrounds the kathode. The positive electrode 

 is connected with the lid of the vessel, which is provided 

 with openings for the escape of the gases resulting from 

 the electrolysis, and is suitably insulated. 



As the electrolysis proceeds, the alkali metal, being 

 much lighter than the molten caustic, rises from the 

 negative electrode and passes into the receiver, the gases 

 escaping around the edges of the cover. The molten metal 

 collects on the surface of the caustic, and is removed by 

 means of a large perforated spoon, the perforations 

 enabling the melted caustic to flow out, while the metal 

 remains in the spoon. As the several vessels are thus 

 skimmed in succession, the fused sodium is collected intn 

 an iron vessel, whence it is poured into moulds, in which 



