CHEMISTRY. (CHEMICAL THEORY.; 



97 



pressure; and molecular volume. A second con- 

 tribution by Van der Waals to the theoretical 

 side of the question, in The Theory of Corre- 

 sponding States, was even more important than 

 his original essay. This theory with the proposi- 

 tions that have been developed has been of the 

 greatest importance in directing experimental in- 

 vestigation and in attacking the difficult prob- 

 lem of the liquefaction of the most permanent 

 gases. In this matter theory has far outrun 

 experiment. In the meantime experiment had 



fone on, and most of the gases had been lique- 

 ed; and the problem had become not so much 

 how to produce intense cold as how to save it 

 when produced from being immediately leveled 

 up by the relatively superheated surroundings. 

 For this purpose the author contrived a system 

 of double- walled vessels, with the space between 

 the walls very highly exhausted. " Vessels of 

 this kind are now in general use, and in them 

 liquid air has crossed the American Continent." 

 Liquid hydrogen that being the last of the 

 gases yet refrigerated is the lightest liquid 

 known to exist, and by far the coldest. It boils 

 at 252.5 C., or 20.5 absolute. Reduction of 

 the pressure by the air-pump brings down the 

 temperature to 258, when the liquid becomes 

 a solid resembling frozen foam, and this by fur- 

 ther exhaustion is cooled to 260, or 13 abso- 

 lute, the lowest steady temperature that has yet 

 been reached. " This gap of 13 might seem at 

 first sight insignificant in comparison with the 

 hundreds that have already been conquered. But 

 to win one degree low down the scale is quite a 

 different matter from doing so at higher tem- 

 peratures; in fact, to annihilate those few re- 

 maining degrees would be a far greater achieve- 

 ment than any so far accomplished in low-tem- 

 perature research." With the liquefaction and 

 evaporation of a gas as much more volatile than 

 hydrogen as that is than nitrogen it might be 

 possible to reach a lower temperature say 5 

 absolute but even a second hypothetical sub- 

 stance of like relative volatility as perhaps 

 helium would not bring the experimenter quite 

 to the point of his ambition. " That the zero 

 will ever be reached by man is extremely im- 

 probable. . . . But supposing all difficulties to 

 be overcome and the experimenter to be able 

 to reach within a feAv degrees of the zero, it is 

 by no means certain that he would find the near 

 approach of the death of matter sometimes pic- 

 tured. Any forecast of the phenomenon that 

 would be seen must be based on the assumption 

 that xthere is continuity between the processes 

 studied at attainable temperatures and those 

 which take place at still lower ones." The 

 speaker doubted whether such an assumption was 

 justified. 



In a communication to the National Academy 

 of Sciences, April, 1902, Prof. T. W. Richards 

 treated of the hypotheses that may reasonably 

 be tried to account for changes in atomic volume. 

 It seems very extraordinary, he held, that not- 

 withstanding the stupendous mass of chemical 

 facts that have been collected and the important 

 researches that have been made in physical 

 chemistry, we are still without knowledge of the 

 nature of a chemical compound and of the man- 

 ner in which its constituents are held together. 

 We are not even certain that they are held to- 

 gether by mutual attractions; for though the 

 evolution of heat \isual when bodies combine in- 

 dicates a satisfaction of mutual forces simul- 

 taneously with the act of combination, there are 

 still cases in which heat is absorbed during com- 

 binations. This fact suggests an inquiry whether 

 VOL. XLII. 7 A 



there may not be other agencies than mutual 

 forces the action of which results indirectly in 

 the formation of chemical bodies; and whether, 

 if so, such agencies may not be a factor even of 

 those combinations in which they are aided by 

 direct forces. When hydrogen and chlorine come 

 together no condensation of which account is 

 taken occurs, although an enormous evolution of 

 heat takes places. The extreme chemical activ- 

 ity of the resulting gas, however, seems to prove 

 that it is not a complete chemical compound. 

 Notwithstanding the great energy with which the 

 ions have approached one another, they are still 

 so active that the case must be regarded as very 

 different from that when a mixture of hydrogen 

 and oxygen loses one-third of its volume in 

 combining. A body may undergo contraction 

 without combining with a different body, as in 

 the case when the vapor of water is cooled. In 

 all such cases heat is plenteously evolved, and 

 molecule unites with molecule, it may be ques- 

 tioned how far the heat of chemical reaction is 

 anything more than heat of contraction. Con- 

 traction does not necessarily consist solely in 

 the approach of atoms toward one another. If 

 an atom is a vortex, it must be in itself elastic 

 and capable of deformation; and it may be so 

 even if it is not a vortex. If atoms are com- 

 pressible the mutual attraction between two 

 atoms would naturally tend to deform them. 

 Hence we have, further, to determine the rela- 

 tion between such deformations and their va- 

 lency. Apparently, highly compressible elements 

 have low valency, while elements of high valency, 

 like carbon, are little compressible. Such con- 

 siderations as these noted should be borne in 

 mind in the construction of new hypotheses 

 upon which experimental investigations are to 

 be based. 



In his presidential address before the section 

 of chemistry of the British Association Prof. 

 Edward Divers, of the Imperial University of 

 Tokio, Japan, presented what he designated as 

 The Atomic Theory without Hypothesis, or 

 divested of" the conception of atoms as discrete 

 particles. He thought that the conception of 

 bodies as not continuous in texture, but as com- 

 posed of discrete minute particles, had been a 

 bar to the full and universal acceptance of Dai- 

 ton's atomic theory, and offered a new view, 

 divested of all reference to the physical constitu- 

 tion of matter, in which only the conditions of 

 chemical equality between substances should be 

 regarded. 



In their study of the theory of radio-activity, 

 E. Rutherford and Frederick Solly observe that 

 all the most prominent workers in the investiga- 

 tion, including M. and Mme. Curie and M. Becque- 

 rel, agree that the phenomenon is the function 

 of the atom and not of the molecule. In the 

 experiments of the authors with the emanation 

 produced by thorium compounds and the prop- 

 erty it possesses of exciting radio-activity on 

 surrounding objects the radio-activity appeared 

 in each case as the manifestation of a special 

 kind of matter in minute amount. The emana- 

 tion behaved in all respects like a gas, and the 

 excited radio-activity it produced as an invisible 

 deposit of intensely active material, independent 

 of the nature of the substance on which it was 

 deposited, and capable of being removed by rub- 

 bing or the action of acids. The position is thus 

 arrived at, that radio-activity is at once an 

 atomic phenomenon and the accompaniment of a 

 chemical change in which new kinds of matter 

 are produced. Before such a view was enter- 

 tained attempts made to explain it on existing 



