NA TURE 



[August 8, 1907 



Section I. — Phys'ologv. 



£ s. d. 



Metabolism of Individual Tissues 40 o o 



The Ductless Glands 30 o o 



Effect of Climate upon Health and Disease ... 35 o o 



Body Metabolism in Cancer ... ... ... 30 o o 



Electrical Phenomena and Metabolism of Arum 



Spadices 10 o o 



Scclioii K. — Botany. 



Structure of Fossil Plants 15 o o 



Marsh \"egetation 15 o o 



Succession of Plant Remains 45 o ° 



Section L. — Educational Science. 



Studies suitable for Elementary Schools ... 10 o 



Corresponding Societies Committee. 



For Preparation of Report 25 o o 



Total 

 SECTION B. 



CHEMISTRY. 



1288 9 



Opening Address bv Prof. A. Smithells, B.Sc, F.R.S., 

 President of the Section. 



The year which has elapsed since the meeting of our 

 Section at York has been eventful in the most melancholy 

 of ways ; the losses sustained by our science have been 

 unparalleled. The passing bell seems to have tolled almost 

 without intermission as one after another of our masters 

 has been taken from us : in Russia, Mendel^eff, Men- 

 schutkin, and Beilstein ; in France, Berthelot and 

 Moissan ; in Holland, Bakhuis-Roozeboom. Whilst in 

 some of these cases we may find consolation in contem- 

 plating a length of life and sustained activity beyond what 

 we might have dared to expect, in others our regret is 

 increased by the sense of untimeliness and of vanished 

 hopes. I am templed to speak of the work of such mighty 

 men as Berthelot and Mendel^eff, to dwell upon the dis- 

 coveries by which they transformed the whole fabric of 

 chemical science ; but this is not the occasion on which 

 to offer an estimate of the labours of those who have 

 passed away. I can only say that in the bond of brother- 

 hood which the pursuit of science establishes among the 

 different nations of the earth we who are Englishmen feel 

 and deplore these losses as our own. 



I must not omit to allude also, as I do with deep regret, 

 to the death in our own country of two such ardent and 

 fruitful workers as Cornelius O 'Sullivan and Robert 

 Warington. 



These words were already in print when again we were 

 called to mourn the loss of one of our greatest men, one 

 who but a year ago was the subject of our special re- 

 joicings, and whose vigour of body and youthfulness of 

 spirit seemed to promise the long continuance of a noble 

 and an extraordinarily fruitful life. We can at least feel 

 thankful that William Henry Perkin lived long enough 

 to learn in what honour and esteem his name was held, 

 not only among his countrymen, but by all the chemists 

 of the world, and by the leaders of those great industries 

 of which he was justly acclaimed the founder. For more 

 than a generation Sir William Perkin had been one of 

 the most familiar figures at the meetings of this Section, 

 and greatly shall we miss his gentle presence, his wise 

 counsel, and his valued contributions. 



I can, perhaps, best occupy your time to-day by attempt- 

 ing to give some account of the present state of the 

 scientific subject to which I have paid most attention. 

 The topic of flame, after a long period of repose, has 

 aroused much interest during late years, and I think we 

 may say that some considerable progress has been made 

 in its elucidation, although in this, as in all other subjects 

 of scientific inquiry, the more closely we scrutinise it the 

 more impressed must we be with what still remains 

 unknown. 



One of the first questions that meet us in the study 

 of flame is that of the temperature at which in any given 

 case the phenomenon becomes evident. Here, I think, a 

 great clarification of view has taken place. The old idea 



NO. 1 97 I, VOL. 76] 



that there exi.sled a fixed temperature at which inflam. 

 niation suddenly took place cannot now be maintained, 

 and the term " ignition temperature " has acquired a 

 different meaning. It is now known that in a very great 

 number of cases a mixture of two flame-forming gases, 

 when gradually raised in temperature, will develop 

 luminosity quite gradually, pari passu, with the chemical 

 combination that is being induced. This phenomenon is, 

 of course, known universally in connection with phos- 

 phorus, but it is not so widely known in connection with 

 other combustible substances. There are some simple 

 tacts that seem as if they never could gain admission to 

 text-books, and I do not think I have known more than 

 a single chemical book that is not likely to leave a student 

 under the impression that the phosphorescence of phos- 

 phorus is an almost unique phenomenon. I do not know 

 how many times the independent discovery has been made 

 that sulphur, arsenic, carbon disulphide, alcohol, ether, 

 paraffin, and a whole host of other compounds, inorganic 

 and organic, will phosphoresce as truly as phosphorus 

 itself; that, in fact, phosphorescent combustion is the 

 normal phenomenon antecedent to what we ordinarily call 

 flame. 



This is, after all, only in harmony with the general 

 truth that chemical combination between two gases does 

 not set in suddenly, but comes into evidence quite 

 gradually as the temperature is raised from a point at 

 which the action, if it occurs at all, is so slow as to be 

 negligible. The increase in the rate of combination is, 

 of course, very rapid as compared with the increase of 

 temperature, a difi'erence of about 10° C. serving to double 

 it. The interval between the beginning of phosphorescence 

 and the production of vigorous flames may therefore be 

 very short. In the case of phosphorus this interval, being 

 from 7° to 60° C, includes ordinary atmospheric 

 temperatures ; hence the phosphorescence of phosphorus 

 is a phenomenon that could not well be overlooked. If 

 the prevailing terrestrial temperature were below 7° C, 

 at which, under normal air-pressure, the phosphorescence 

 of phosphorus ceases, it is possible that this element might 

 never have acciuired its peculiar reputation ; it would not 

 have shone in the dark, and in lighting it with a taper 

 the phosphorescent interval would have been passed over 

 as quickly as is ordinarily the case in the ignition of 

 sulphur, paraffin, and other common combustibles. To 

 make phosphorescence apparent in these last cases it is 

 necessary to take special care to heat up a mixture of 

 the combustible gas and air gently, and to maintain it at 

 a temperature approaching, but not quite reaching, that 

 of ignition. There is no simpler way than that used by 

 Sir William Perkin, who brought the combustible substance 

 near to, or in contact with, a massive metal ball previously 

 heated to the suitable temperature. 



The change from phosphorescence to ordinary flame is 

 not sudden, but (he appearance of ordinary flame is the 

 end point of a continuous, though rapid, development. 

 This end point is the temperature of ignition. What, then, 

 determines the temperature of ignition? The answer to 

 this question has been given with characteristic concise- 

 ness by van 't Holf as " the temperature at v.'hich the 

 initial loss of heat due to conduction, &c., is equal to the 

 heat evolved in the same time by the chemical reaction." 



We may obtain a clear idea of the meaning of tempera- 

 ture of ignition by supposing a combustible mixture of 

 gases such as that of air and the vapour of carbon 

 disulphide to issue through an orifice into an indifferent 

 atmosphere. If we surround the orifice by a ring of 

 platinum wire, which is gradually heated up by a current 

 of electricity, a flame will gradually make its appearance. 

 If, as soon as this is observed, the heating of the wire by 

 the current be discontinued, the flame will disappear; it 

 is, in fact, not self-supporting, but depends on the accessory 

 supply of heat through the electrically heated wire. If 

 now we raise the ring to a higher temperature we shall 

 get a brighter flame, owing to an increased rate of chemical 

 action, and at last we shall reach a point where it is 

 possible to cut oflf the electric current without causing at 

 the same time the extinction of the flame. This is the 

 true temperature of ignition, the temperature at which the 

 reaction proceeds at a rate just sufficient to overbalance 

 the loss of heat by radiation, conduction, and convection 



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