74 



NATURE 



[November 4, 191 5 



The section met on three mornings and two after- 

 noons, so that although the whole meeting was shorter 

 than has hitherto been customary, chemists actually 

 devoted more time to the consideration of their sub- 

 ject, and the usually rather risky experiment of after- 

 noon sessions proved entirely successful, chiefly no 

 doubt because social counter-attractions were absent. 



Two mornings were occupied by discussions, one 

 dealing with smoke and its prevention, the other with 

 homogeneous catalysis. Manchester, to the residents 

 in the rural parts of these islands, shares with Shef- 

 field an unfortunate reputation for griminess ; there- 

 fore the discussion on smoke was peculiarly apposite. 

 Though many efforts are made to combat the smolve 

 evil, not only because of its noxious effects, but also 

 because of the enormous waste due to the huge quan- 

 tities of valuable fuel constantly being poured into our 

 atmosphere, much still remains to be done towards 

 the economic utilisation of our fuel supply. The dis- 

 cussion was opened by Mr. E. D. Simon, chairman 

 of the Manchester Air Pollution Advisory Board, with 

 a paper on "Lines of Research in Smoke Abatement." 

 Briefly, it may be said that it is only by a systematic 

 investigation of the amount of deposit, its nature, and 

 the diminution of light caused by the smoke cloud at 

 different observing stations near our great cities, that 

 the damage done can be evaluated and the origin of 

 the smoke determined. 



Though factories and works contribute greatly to 

 the nuisance, the domestic chim.ney, so dear to the 

 Briton, appears to be the offender most capable of 

 correction, by the use of gas fires, coke fires, and 

 semi-coked coal. Mr. Simon put forward the plea 

 that the British Association should appoint a com- 

 mittee to co-ordinate the work of local municipal com- 

 mittees who are prosecuting research on the most 

 efficient forms of domestic heating and the economical 

 and smokeless use of fuel in general. 



The position, so far as Manchester is concerned, was 

 further explained by Mr. Haldane Gee and Prof. 

 Knecht, the former reviewing the work carried out in 

 Manchester during recent years, and the latter giving 

 an account of Manchester smoke from the chemical 

 point of view. 



Prof. Wynne gave a number of statistics for the city 

 of Sheffield based on an investigation of the rain- 

 water collected in various soot gauges, from which 

 it appears that if the district where the armament 

 works are situated be excepted, the results for the 

 other portions of the city show a remarkable approach 

 to uniformity independent of the direction of the pre- 

 vailing wind. If the contribution of house fires to the 

 air pollution can be based on the proportion of tar and 

 ammonia collected in the rain-water, no material differ- 

 ence could be traced between the winter and summer 

 six months. 



The effect of smoke on vegetation was considered 

 by Prof. Ranwez and Mr. Ruston, the first describing 

 the more general effects on trees and plants, while the 

 second paid special attention to the reduction of sunlight, 

 action of acids on leaves, soot formation, enzyme, and 

 bacterial action. Smoke pollution is apparently an 

 inhibitor of the enzymic chemical changes which occur 

 in plants, and corvsequently near cities our plants are 

 less bright, form less reserves, and produce seeds with 

 diminished germinating capacity and energy, all which 

 Is but too apparent to the gardener in our urban 

 districts. The electrical precipitation of smoke also 

 came In for comment, and some slides shown by Mr. 

 Vernon Harcourt incidentally illustrated well the pos- 

 sibility of combining economic fuel combustion on a 

 domestic hearth with the artistic merits of the English 

 fireplace, a point too Infrequently considered, but most 

 of the other speakers were concerned with the necessity 

 for taking some action, comoulslon if necessary, to 

 NO. 2401, VOL. 96] 



force the inhabitants of this country to be more 

 economical in fuel. 



The outcome of the whole discussion, which in many 

 ways was supplementary to that at the Birmingham 

 meeting, was that a committee to consider the whole 

 question of the economic use of fuel and smoke pre- 

 vention was appointed by the Chemical Section. 



The discussion on homogeneous catalysis was opened 

 by Prof. Lewis, who advanced a new theory based 

 fundamentally on Planck's quantum hypothesis. The 

 physical idea underlying the theory is that ordinary or 

 "thermal" reactions are due to the infra-red radiation 

 which is necessarily present throughout any material 

 system in virtue of its temperature. When a reaction 

 proceeds without the addition of a catalyst, it Is to be 

 inferred that the density of the radiation " naturally " 

 present In the system Is sufficient to activate the mole- 

 cules taking part in the reaction. Each type of mole- 

 cule has its own characteristic absorption and emission 

 bands in the Infra-red, and can only be activated chem- 

 ically by the absorption of radiant energy the frequency 

 of which corresponds to one or more of these band 

 positions. The function of a positive catalyst Is to 

 Increase the radiation density of the frequency which 

 corresponds to that of the reacting substance, a nega- 

 tive catalyst reduces the energy frequency of the "use- 

 ful" frequency, and so hinders the rate of decomposi- 

 tion of the substance. By applying Planck's quantum 

 theory to the simple case of a mono-molecular reaction 

 Prof. Lewis deduced the following expression for the 

 variation of the velocity constant (fe) with the tem- 

 perature (T) : — • 



d\og k _^hv 



where N is the number of molecules in one gram- 

 molecule, h Is Planck's constant, R the gas constant 

 per gram-molecule, and v the characteristic infra-red 

 vibration frequency of the reacting substance. By the 

 aid of this expression values for v can be calculated 

 from temperature coefficient measurements. From 

 measurements on the inversion of cane-sugar and 

 hydrolysis of methyl acetate It was calculated that v 

 corresponded to a wave-length \-i \t. and i-g /x values 

 in fair agreement with the absorptions determined by 

 Coblentz from transmission spectra. Prof. J^wis sug- 

 gested that as aqueous hydrochloric acid possesses a 

 band in the same region, Its known positive catalytic 

 effect Is due to this cause, as also the catalytic effects 

 due to pure and mixed solvents. 



By considering that only those molecules react which 

 reach a "critical" condition, namely, one in which 

 they acquire a certain energy In excess of the average 

 energ}' per molecule in the system, a view put forward 

 by Marcelin in a series of papers on reaction velocity, 

 Mr. J. Rice deduced a very similar expression for the 

 relation of fe to T to that given by Prof. Lewis. Con- 

 siderable forces must hold the molecules together when 

 near each other, but the law of force must be such that 

 at a " critical " distance the attraction must weaken 

 and change to repulsion, thus Implying that the poten- 

 tial energy between two molecules is greatest at the 

 critical distance apart. By assuming that the forces 

 Involved are electromagnetic and subject to modifica- 

 tion due to the changes in radiation density produced 

 by the catalyst, results are obtained in agreement with 

 the existing experimental data. 



Prof. F. Francis exhibited and described an apparatus 

 for measuring the velocity of catalysis of nitroso- 

 triacetonamine and allied derivatives by hydroxyl ions, 

 based on the determination of the pressure of the 

 nitrogen evolved. The method was also of use to 

 determine the concentration of the hydroxyl ions. He 

 also described the curious effect of neutral salts, and 

 pointed out that nearly the same quantitative retarda- 



