Decembek 29, 1898J 



NA TURE 



in water and ort^anic liquids have been gradually accumulated 

 by the work of Blagden, Kiidorff, Coppet and Raoult, extending 

 from about 1 780 to the present time, but no general explanation 

 of them was brought forward until Van 't Hoff advanced the 

 remarkable theory that a dissolved substance was in a condition 

 somewhat analogous to that of a gas, the solvent substance 

 serving the part of the vessel in which the gas is confined, but 

 also exerting other effects. 



He further gave strong reasons for believing that substances 

 in dilute solution obeyed the same laws that gases do — i.e. the 

 laws of Boyle and Charles for temperature and pressure. 

 Several other theories of solution, besides what may be termed 

 the gaseous theory, have been proposed. Notwithstanding that 

 some weighty objections can be urged against this theory, it is 

 remarkable that we can by aid of it predict the numerical values 

 for the fall of the freezing point of different solvents produced 

 by the solution of other substances, provided that we know the 

 latent heat of fusion of the solvent. 



On applying the .same reasoning to alloys, we find that the 

 theory holds good, as the table below shows.' We see from 



Observed Repression ill the Freezing Point of a Solvent Metal, 

 caused liyt/ie Addition of One Atomic per cent, of a Second Metal. 



this table that in no cases are the observed depressions of the 

 freezing points greater than those calculated from the theory, 

 but in many cases they fall below this quantity ; this latter fact 

 admits of explanation. 



On the theory of Van 't Hoff it is necessary that when a 

 solution begins to freeze the pure solvent should separate out 

 first. This admits, in case of aqueous solutions, of simple 

 proof; for if we take a dilute solution of potassium of per- 

 manganate and make it freeze slowly, we find that pure colour- 

 less ice separates out on the walls of the vessel, whilst the 

 purple permanganate is concentrated towards the centre. This 

 experiment led Neville and myself to try if a similar state of 

 things could be shown fur metallic alloys. 



We have great pleasure in bringing before the Roya! Institu- 

 tion this evening the first announcement of the results we have 

 obtained. For this purpose we took two metals, gold and 

 sodium, the former being very opaque to X-rays, whilst the 

 latter is very transparent to them. A quantity of sodium was 

 melted in a tube, and gold dissolved in it to the extent of about 

 ten per cent. The alloy was then allowed to cool extremely 

 slowly, and sections (about J inch thick) were cut from different 

 parts of the solid alloy and placed between thin plates of 

 aluminium to protect them from the air. These sections were 

 then placed on a photographic plate, enclosed in a light tight 

 bag, and exposed to the action of the X-rays. On developing 

 the plate we found a complete picture of the inside of the alloy. 

 Positives obtained from these negatives are thrown upon the 

 screen. The sodium is seen to have crystallised out in plates, 

 as is evident from its transparency, whilst the opaque gold is 

 seen to have become concentrated in the mother liquor between 

 these plates, where it finally solidified along with some of the 

 sodium. 



Very similar results are produced with other pairs of metals, 

 such as alurainium'and gold and aluminium and copper. Behrens, 

 Roberts-Austen, Osmund and others have examined alloys, 

 after superficial etching, with high microscopic powers, and they 

 find a similar separation of the constituents. 



We thus see that solution of metals in one another follows 



; caIculation,_7'/rt'tf Heycock and Neville, Chan. 

 f Progress, October 1895. 



NO. 1522, VOL. 59] 



extremely closely the same laws that regulate solutions with 

 which we are ordinarily familiar. I should like to state here 

 that the matter of this lecture is largely drawn fiom the work 

 carried out by Mr. Neville, F. R. S. , and myself during the past 

 six years. 



UNIVERSITY AND EDUCATIONAL 

 INTELLIGENCE. 



Oxford. — The electors to the Linacre Professorship of Com- 

 l^aralive Anatomy will pioceed to an election in the course of 

 Hilary Term, and candidates are desired to send in their names 

 to the Registrar of the University not later than January 31, 

 1899. The Board of Electors consists of the Visitor of Merton 

 College (the Archbishop of Canterbury), the Presidents of the 

 College of Physicians and the College of Surgeons, the Wayn- 

 flete Professor of Physiology, the Regius Profes.sor of Medicine, 

 an elector appointed to represent Merlon College, and an 

 elector appointed to represent the Hebdomadal Council. 

 The Hon. G. C. Brodrick, Warden of Merton, has been ap- 

 pointed by Merton College, and the Dean of Christchurch by 

 the Hebdomadal Council. 



The electors to the Sedleian Professorship of Natural Phil- 

 osophy, vacant by the resignation of Prof. Price, will also pro- 

 ceed to an election in the course of Hilary Term, and names 

 of candidates are to be sent in not later than January 31. 

 The Board of Electors consists of the Vice-Chancellor, the 

 President of the Royal Society, the Provost of Queen's College, 

 the Professor of Experimental Philosophy, Savilian Professor 

 of Geometry, an elector appointed to represent Queen's College,, 

 and an elector appointed to represent the Hebdomadal Council.. 



Prof. Elliot and Prof. Riicker have been chosen as the last- - 

 mentioned electors. 



The Calendar of University College, London, for the session. 

 1898-99, has just been received. The purpose of the College, 

 as expressed in the Act of 1S69, whereby the College was re- 

 incorporated with additional powers, and divested of its pro- 

 prietary character, is "to afford at a moderate expense the 

 means of education in literature, science, and the fine arts, and 

 in the knowledge required for admission to the medical and 

 legal professions, and in particular for so affording the means ot 

 obtaining the education required for the purpose of taking the 

 degrees now or hereafter granted by the University of London." 

 During last session the following new departments were created : 

 Laboratory of Experimental Psychology, Pender Chair of 

 Electrical Engineering, the Edwin Chadwick Chair of Muni- 

 cipal Engineering. It is interesting to note that in the depart- 

 ment of applied mathematics. Prof. Pearson gives, in the place 

 of advanced class examinations, subjects for dissertations refer- 

 ring to the mathematical theory of statistics. 



Mr. W. C. McDonald's benefactions to the Mcflill Uni- 

 versity, Montreal, have often been the subjects of notes in these 

 columns, and last week we recorded that he had received the 

 honour of a knighthood in recognition of his gifts to philan- 

 thropical and educational objects in Canada. Mr. McDonald's ■ 

 princely gifts to the McGill University include 20,000 dollars- 

 to the Workman endowment for mechanical engineering ; the- 

 erection of the W. C. McDonald engineering building, valued, 

 with its equipment, at 350,000 dollars, and an endowment for 

 its maintenance ; the endowment of the chair of electrical 

 engineering with the sum of 40,000 dollars ; the erection and 

 endowment of the phy.sics building, valued at 300,000 dollars, 

 and two chairs of physics with endowments amounting to 90,000 

 dollars; the endowment of the faculty of law with 150,0001 

 dollars ; the endowment and equipment of the chair of archi- 

 tecture ; a further sum of 150,000 dollars for the maintenance- 

 of the engineering building ; 50,000 dollars towards the endow- 

 ment of the pension fund ; and the erection of a new building 

 for the Department of Chemistry, Mining, and Agriculture, at 

 a cost of 500,000 dollars, making the total amount contributed 

 to the institution upwards of 1,600,000 dollars. 



The Executive Committee of the Central Welsh Board have- 

 unanimously passed the following resolutions, among others, 

 referring to the Board of Education Bill, and have forwarded 

 copies to the Education Department and the Charity Commis- 

 sion, with an intimation that they will be brought before the 



