July 6, 1893] 



NA TURE 



237 



series of selected specimens has been arranged and exhibited at 

 various soirjes. This exhibition series is being enlarged. 



Owing to the generosity of Mr. J. P. Thomasson, who has 

 made a second donation of ;,f 250 for this purpose, it has been 

 possible for the council to retain the services of Mr. Halt for 

 fishing inquiries in the North Sea for a second year. 



Mr. Garstang has been appointed for a second year to super- 

 intend the collection, preservation, and supply of material. 

 The character of the specimens supplied by the laboratory has 

 improved very greatly under his care. 



Mr. Cunningham has continued his observations on the rate of 

 growth and probable ages of young fish, a paper on which was 

 published in the November number of the Association's journal. 

 He has also continued his experiments on the colouration of the 

 under-side of flat-fishes. Since Christmas he has been occupied 

 in an inquiry into the question of the destruction of immature fish, 

 the first results of which appear in the May number of the 

 journal. 



Mr. Cunningham has also succeeded in artificially fertilising 

 the eggs of the flounders which he has reared in the laboratory 

 tanks during the last three years from a length of half an inch ; 

 the eggs developed, and the larvae were artificially fed for ten 

 days after the absorption of the yoll<-sac. This result is of great 

 importance and interest. 



Mr. Holt has been at work now for eighteen months upon an 

 investigation of the fisheries of the North Sea, and his papers in 

 the journals for November and May supply a large amount of 

 important information. The Council contribute to the expenses 

 of the Cleethorpes Aquarium of the Marine Fisheries Society 

 (Grimsby) in return for Mr. Holt's use of their laboratory and 

 tanks. 



Mr. Garstang has captured a large number of rare forms 

 daring the past year, and he has added five new species to the 

 list of the British fauna. As a result of his work daring the 

 past year, an intimate knowledge of the localities of the fauna 

 has been acquired, so that specimens can be obtained without 

 delay. 



Tne receipts for the past year include the annual grants from 

 H.M. Treasury (^1000) and the Worshipful Company of Fish- 

 mongers (^400); annual subscriptions have produced ;£'i6o, 

 composition fees/i6, the rent of tables at the laboratories, £l^, 

 the sale of specimens ^£'205, and the admission to the tank-rojm 

 iC^o, the total amounting, with lesser sums, to ;^2I99. 



The Vice-Presidents, Officers, and Council proposed by the 

 Council for 1893-94 are :— President : Prof. E. Ray Lankester, 

 F.R.S. ; Vice-Presidents: The Dake of Argyll, K.G., K.T., 

 K.R.S., the Duke of Abercorn, K.G., C.B., the Earl of St. 

 Germans, the Earl of Morley, the Earl of Ducie, F.R.S., Lord 

 VValsingham, F.R.S., Lord Revelstoke, the Right Hon. A. J. 

 lialfoar, M.P., F.R.S., the Right Hon. Joseph Chamberlain, 

 .M.P., Prof. G. J. Allman, F.R.S., Sir Edward Birkbeck, 

 Bart,, M.P., Sir Wm. Flower, K.C.B., F.R.S., the Right 

 Hon. Sir John Lubbock, Bart., M.P., F.R.S., Prof. Alfred 

 Newton, F".R.S., S r Henry Thonpson, Rev. Canon Norman, 

 F.R.S., Captain Wharton, R.N., F.R.S.; Council— elected 

 Members: F. E. Beddard, F.R.S., Prof. F. Jeffrey Bell, Prof 

 W. A. Herdman, F.R.S., Sir John Evans K.C.B,, F.R S , 

 A. C. L. G. Giinher, F.R.S., Prof. A. C. Haddon, Dr. Syd- 

 ney J. Hickson, Prof. W. C. Mcintosh, F.R.S., Right Hon. E 

 Majoribanks, M.P., E. B. Poulton, F.R.S., P. L. Sclater, 

 l-.R.S., Adam Sedgwick, F.R.S., Prof. Charles Stewart, Prof 

 W. F. R. Weldon, F.R.S., Hon. Treasurer : E.L. Beckwith ; 

 I ion. Secretary : G. Herbert Fowler. 



THE CONDITIONS DETERMINATIVE Of 

 CHEMICAL CHANGE.^ 



>^OTWITHSTANDING the large amount of evidence now 



placed on record that substances commonly supposed to be 



apable of directly interacting do so only in the presence of at least 



>ne other substance, chemists do not appear to have arrived at any 



lear and consistent understanding of the conditions determina- 



iive of chemical change : as each fresh case is recorded, we con- 



inue to express surprise, overlooking the fact that Faraday, in 



Ills early ''Experimental Researches in Electricity," clearly 



ii.resaw what the conditions were, and that but a slight exten- 



' Reprinted from Ihe Proceedings of the Che nical Society, No 125. 



NO. 1236, VOL. 48] 



sion of his generalisations is needed to frame a comprehensive 

 theory. The subject is of such importance that it appears to 

 me desirable to discuss the bearing of recent observations, 

 especially as they to some extent necessitate the modification of 

 views that I have expressed elsewhere, and in order to attract 

 the attention of physicists, to whom we must now look for 

 guidance in these matters. 



Eight years ago, in the course of the discussion on Mr. H. B. 

 Baker's communication on combustion in dried gases 

 (Proc. Chem. Soc. , 1885, 40), I defined chemical action as 

 reversed electrolysis : in other words, in ord^r that chemical 

 action may take place, it is essential that the system operated on 

 comprise an electrolyte. I then pointed out that as neither 

 hydrogen nor oxygen was an electrolyte, a mixture of only these 

 two gases should not be explosive ; and, moreover, as water was 

 not an electrolyte, and it was scarcely probable that water and 

 oxygen or hydrogen would form an electrolyte, it was difficult to 

 understand how the presence of water pure and simple should 

 be of influence in the case of a mixture of hydrogen and oxy- 

 gen. This forecast has since been verified, the remarkable 

 series of experiments carried out by V. Meyer in conjunction 

 with Krause and Askenasy having clearly demonstrated that the 

 formation of water from hydrogen and oxygen takes place at an ir- 

 regular rate, and is, therefore, dependent on the presence of a 

 something other than water — I imagine an acid impurity. But this 

 is a consideration which has not yet received the proper attention, 

 and it is, therefore, desirable to emphasise its importance by 

 reference to other cases. Mr. Baker's recent preliminary note 

 on the influence of moisture in promoting chemical action [ante, 

 p. 229) affords several interesting examples : — Thus, he states 

 that neither does hydrogen chloride combine wilh ammonia, nor 

 is nitric oxide oxidised by oxygen if moisture be excluded. 

 In the former case, the addition of water should suffice to deter- 

 mine the combination, as water and hydrogen chloride together 

 forma "composite electrolyte" [cf. Roy. Soc. Proc, 1886, No. 

 243, p. 26S) ; as neither nitric oxide nor oxygen, however, forms 

 a composite electrolyte with water, in this cise water alone 

 should not determine the occurrence of change ; but if, by the 

 introduction of a trace of " impurity " in addition to water the 

 presence of a composite electrolyte were secured (however high 

 its resisfance, owing to the smallness of the amount of "im- 

 purity "), action would set in, and when once commenced would 

 proceed at an increasing rate, as nitric acid would be formed 

 and the resistance of the electrolyte would consequently 

 diminish. On this account it will be a task of exceeding diffi- 

 culty to experimentally demonstrate that nitric oxide and oxy- 

 gen are inactive in presence of water alone ; but there can be 

 no doubt that such must eventually be admitted to be the case, 

 provided always that it is permissible to extrapolate Kohlrausch's 

 observatio.is, and to conclude from them that pure water is a 

 dielectric. The gradual increase in the rate of change here 

 contemplated corresponds to the period of induction observed 

 by Bunsen and Roscoe in their observaions on the interaction 

 of chlorine and hydrogen ; the statement recently made by 

 Bodenstein and V. Meyer {Berichte, 1893, 1146) that a mixture 

 of chlorine and hydrogen behaves irregularly on exposure to 

 light is a valuable confirmation of Pringsheim's observations, 

 and there is now no room for doubt that pure chlorine and hydro- 

 gen would be incapable of interacting. That no such irregu- 

 larity is observed on heating iodine with hydrogen is not 

 surprising, as hydrogen iodide would be formed from the very 

 outset, and the electrolyte present would exert a minimum 

 resistance almost at once. There is, however, a significant 

 difference in the behaviour ofthe two mixtures, as hydrogen chlor- 

 ide should behave as hydrogen iodide, so that the problem is but 

 incompletely solved : it may be that the one mixture was more 

 nearly pure than the other, or it may be that the formation of 

 hydrogen chloride from hydrogen and chlorine, under the 

 influence of light, is dependent on the presence of some par- 

 ticular substance, together with water, and does not take place 

 under the influence of any substance capable of forming a com- 

 posite electrolyte with water ; probably, however, the difference 

 observed is chiefly due to the fact that only one of the actions is 

 reversible under the conditions prevailing in the experiments. 



Lastly, attention may be directed to the foimation of sulphuric 

 oxide from sulphurous oxide and oxygen, which is readily 

 effected in presence of a catalyst, such as finely divided 

 platinum; it cannot be supposed that the mere presence of 

 platinum would condition the occurrence of change, and doubt 

 less moisture is also necessary, the platinum or other catalys 



