Sept. 14, 1888.] 



SCIENTIFIC NEWS. 



287 



that should not be practised without more thought. Too often 

 teachers persisted in putting tormenting questions to their pupils. 

 Teachers should impart their knowledge in such a simple, intelli- 

 gent, direct, and straightforward manner so as to at once produce 

 an impression on the youthful mind. The questions should come 

 from the pupil, and not from the teacher. 



Mr. West (Bournemouth) thought it was not much good trying 

 to give definite scientific teaching to boys before they were of the 

 public school age. 



Mr. Lascelles, Chemical Master .at Harrow, considered the 

 lecture system interspersed with catechism the best. He did not, 

 however, recommend the abstract teaching of chemistry to boys; he 

 believed in imparling to them general facts. 



Mr. Hugh Madan (Exeter), Mr. Harvey Hichen (Radley), 

 Mr. Veley (Oxford), also took part in the discussion. 



The President, in adjourning the sitting, expressed a hope that 

 by another year the Committee would be in possession of some 

 definite recommendations to be submitted to the head masters of 

 the great public schools throughout the country. 



Monday, September ioth. 

 Professor Tilden, F.R.S., presiding. 



Professor H. E. Armstrong, F.RS., opened a discussion on 

 Valency. He said : This was undoubtedly one of the most important 

 and at the same time most difficult problems chemists have to solve. 

 It was clear of course to every chemist that the determination of 

 valency in any particular element involved the constitution of that 

 element. And of course the determination of the constitution in- 

 volved the idea of valency. The problem presented the greatest 

 difficulties, and all people who were not blind followers of any par- 

 ticular system must admit that in regard to it chemists have yet a 

 great deal to learn. The meaning of the term chemical action must 

 be largely extended, and chemists would have ultimately to regard 

 the physical action involved in the changes as essentially chemical 

 in their nature. Chemical action must be defined as a change in the 

 molecular condition. No doubt chemists had got too much in the 

 habit of treating the nature of chemical affinity from too narrow a 

 point of view. A very considerable widening of our conception in 

 this regard must be insis'ed upon. There were two forms of valency 

 to be looked at — fixed valency and variable. And he would point 

 out that the only definite conception of valency was practically that 

 which involved the acceptation of the doctrine of fixed valency. But 

 before they could come to any de finite conclusion on the subject there 

 must be a greater interchange of opinion between chemists and phy- 

 sicists. It was practically hopele:S for the chemists to endeavour to 

 solve the problem by themselves. And one of the greatest difficulties 

 that surrounded the question was the difficulty in putting the 

 chemists' investigations in such a form as to be perfectly intelligible 

 to those outside the circle. Dr. Williamson had advocated the view 

 that in a large number of double salts we were to assume that there 

 was a redistribution of the constituent elements, so that the consti- 

 tuent elementsall become associated with one central element. The 

 doctrine of fixed valency assumed that the elements in a great many 

 cases are of a different order, and that in a compound there is 

 no sacrifice of the original substances, but that they are still 

 present. The assumption is that there are the constituent radicals 

 of the compound, and that they are held together in a special way 

 by the mere juxtaposition of the molecules. The great question to 

 decide upon was in relation to the existence of these two classes of 

 compounds. It involved the distinction between atomic and mole- 

 cular compounds, and that led up to the question, In what manner are 

 the constituent radicals of the molecular compounds held together ? 

 One view he particularly desired to advance was one which involved 

 what might be termed the property of supervalency in certain 

 elements. Valency might be described as the atom-fixing power of 

 an element — the power of associating distinct elements in a single 

 atom. Unless they admitted this, the problem must be given up ; 

 from this point of view a chlorine was a super-valent element, and 

 they must admit that the chlorine atom was capable of entering into 

 association with more than one other atom. He did not think, 

 however, that mere discussion would help them much, and until they 

 agreed upon some definite line of going to work, the problem would 

 be as far from solution as ever. 



The President, in the course of a few remarks, said : Of course, 

 neither Professor Armstrong nor any one else could expect that 

 every chemist would agree with him in all the views he took, but 

 he should like to say how fully he agreed with him with regard to 

 the statement that it was impossible to give any exact definition of 

 chemical action, or indeed of a chemical compound. The discus- 

 sion of the question of valency peculiarly involved the theory of 



what is chemical action or chemical combination. One important 

 omission in Dr. Armstrong's argument was the fact that chemical 

 combinations depended almost entirely on the temperature. 



Frofessor A. W. Williamson, F.R.S.,said: Chemists well knew 

 that it was but comparatively recently that their attention had been 

 drawn to the fact that there were atoms which differed from others 

 in the complexity of the group they held together, the power of 

 uniting together various atoms and combining them being possessed 

 in a very different degree. Naturally chemists had made various 

 attempts to explain these phenomena, but, unfortunately, in many 

 cases it had only been a case of putting on intellectual blinkers toshade 

 the horizon so as to limit the view to the particular portion in regard to 

 which pet theories existed. A remarkable instance of variable 

 valency was afforded by nitrogen, which was found in chemical 

 compounds with three and sometimes with five monads. And the 

 important fact must not be lost sight of that in proportion as the 

 temperature was raised did they find the power of holding many 

 atoms in combination diminish. There were two classes of com- 

 pounds which had different valencies, and one class was quite as 

 characteristic of compounds in the same degree as the other. 

 Nothing but phrases could be used to establish a distinction 

 between them. With regard to some other points whieh claimed 

 very special attention, they could not fail to notice that the bodies 

 in which many atoms were found grouped together chemically were 

 of rare occurrence. The changes of temperature ought to be par- 

 ticularly noted, in that it diminished the power of the one central 

 atom. But before they made progress with so complex and diffi- 

 cult a subject they must proceed on the clear statements of ascer- 

 tained facts, and with as little supposition as possible. 



Lord Rayleigh, Sec.R.S., said it was a very wide question that 

 had been touched upon as to how far it was desirable to introduce 

 new names for expressing physical or chemical results. He thought 

 that both advantages and disadvantages would be experienced. No 

 doubt it would please physicists if every element could be deter- 

 mined as having a fixed valency. He, however, failed to see how 

 they could get over such phenomena as that afforded in ammonium 

 chloride. 



Dr. Gladstone, F.R.S., suggested that the refraction and dis- 

 persion of bodies was an object that would bear largely upon the 

 consideration of some of the difficult questions that had been 

 brought forward. It ought to be a most powerful argument in ex- 

 plaining some of the peculiarities of combination. Physical pheno- 

 mena and chemical facts sometimes agreed, and he thought they 

 would have to note this relationship more definitely before they 

 came to complete agreement on so complex and difficult a subject. 



Professor Sterry Hunt said he had maintained for years that 

 all changes, such as condensation, etc., and those remarked upon by 

 Dr. Gladstone, were essentially changes in their nature, and that in 

 the case of chemical combination it was nothing more than a dis- 

 position which all matter had to unite and condense— the tendency 

 to intrinsic condensation. 



Dr. Morley and other members having spoken on the subject, 

 Professor Armstrong briefly replied. 



The other papers read were as under : — 



Evidence of the Quantivalence of Oxygen, derived from the Study 

 of the Azo-Naphthol Compound*. By Professor R. Meldola, F.R.S. 



Theory of Solution. Professor Sterry Hunt. 



The Cornpositicn of Copper-tin Alloys. Mr. A. P. Laurie, 

 F.C.S. 



Analysis of Ancient Mortar from the Roman Wall of London. 

 Mr. S. Sfiller, F.C.S. 



Action of Acids on Copper. Mr. V. H. Veley, F.C.S. 



Recoi>ery of Ammonia and Chlorine in the Ammonia-soda Process. 

 Mr. Fred. B\le. 



Tuesday, September ii. 



Professor Tilden, F.R.S. , presiding. 



After the report of the Committee on Isometric Naphthalene Deri- 

 vatives had been received from Professor Armstrong, Dr. J. H. 

 Gladstone read some Notes on the Molecular Weight of Caoutchouc 

 and other Colloids, and Professor Emerson Reynolds described 

 the Properties of some New Silicon and Thiocarbamide Compounds 

 and the method he had followed in obtaining the same. 



In a paper on The Action of Light on Water-colours Dr. Richard- 

 son discussed the effect of light on colours, and drew attention to 

 the very important part played by moisture in assisting their decom- 

 position. Colours he divided into two groups : those that bleach 

 by oxidation under the combined influence of light, air, and moisture ; 

 and those on which light exerts a reducing action which is indepen- 

 dent of the air, and in some cases takes place in the absence of 

 moisture. The author condemned as unsafe those pigments which 



