102 



CHEMISTRY. (CHEMICAL PHYSICS.) 



that the hypothesis is a useful one in that it fur- 

 nishes the only intelligible explanation of such 

 phenomena as 'those of diffusion, expansion, and 

 heat. Reviewing the criticisms that have been 

 made against the theory, he replies to them, and 

 cites certain experiments that have been made 

 recently such as those of Sir \Y. C. Roberts-Aus- 

 ten on the interpenetration of gold and lead, and 

 experiments with electrified, highly rarefied gases 

 which seem to bear in favor of it, and concludes 

 that. " in spite of many outstanding difficulties, 

 in spite of the tentative nature of some of our 

 theories, the atomic theory unites so many facts, 

 simplifies so much that is complicated, that we 

 have a right to insist at all events, till an equally 

 intelligible rival hypothesis is produced that the 

 main structure of our theory is true; that atoms 

 are not merely helps to puzzled mathematicians, 

 but physical realities." 



Among the various theories of solution, that of 

 Van't 11 off, which regards the dissolved substance 

 in a dilute solution as existing in a gaseous state, 

 has found much favor. But determinations of 

 molecular weight derived by this hypothesis do 

 not agree, especially in the case of electrolytes, 

 with those obtained by other methods or deduced 

 from the chemical formulae. This circumstance, 

 coupled with the fact that the least electromotive 

 force suffices to generate a current in an electro- 

 lj-te, had already led Clausius to replace the hy- 

 pothesis of Grotthus by other theories; but Ar- 

 rhenius, observing that the anomalies in ^tlie 

 osmotic pressure and the freezing-points occur ex- 

 clusively in solutions of electrolytes, was led to 

 the hypothesis that these contain the acids and 

 salts in a state of dissociation, increasing with 

 the dilution. The hypothesis of electrolytic dif- 

 fusion has been put by Profs. Angelo Battelli and 

 Annihale Stefanini to a variety of tests in con- 

 nection with the mechanical phenomena of os- 

 motic pressure, optic phenomena, thermal phe- 

 nomena connected with freezing-point and boil- 

 ing-point determinations, and electric phenomena. 

 Many of the results favor the hypothesis of the 

 existence of free ions in solutions, but others are 

 difficult to reconcile with this theory. 



Another theory of solutions is suggested, with 

 a new conception of thermal pressure, by Mr. G. 

 N. Lewis in the Proceedings of the American 

 Academy of Sciences. The theory according to 

 which the thermal pressure of any phase is equal 

 to the pressure which the substance would exert 

 if under the same conditions as a perfect gas, 

 arose in the consideration of certain remarkable 

 general laws which treat of heterogeneous equi- 

 librium In which the several phases are subject to 

 different pressures. The author believes that the 

 same assumption is alone sufficient to explain all 

 the laws of dilute solutions. 



From a large number of experiments made in 

 the study of the relations between the electric con- 

 ductivity and the chemical character of solu- 

 tions, Prof. John Gibson has deduced as the broad 

 principle underlying the results obtained, that in 

 solutions intermolecular reactions tend toward 

 maximum specific electrical conductivity. 



The' electrolytic dissociation theory of Arrhe- 

 nius is severely criticized by Prof. Kalilenberg in a 

 paper published in the Bulletin of the University 

 of Wisconsin (No. 47, February, 1<)01), in which 

 experimental evidence in contradiction of it is 

 brought forward. Prof. Kalilenberg has remeas- 

 ured the conductivity of a number of electrolytes 

 at zero and 05, and has calculated the degree of 

 dissociation from the measurements as well as 

 from determinations of the lowering of the freez- 

 ing-point and the rise of the boiling-point. The 



two sets of results he has obtained are not con- 

 cordant, a fact which the author regards as bear- 

 ing very strongly against the dissociation theory. 

 Nature maintains, however, that this theory, even 

 though it has not met with universal acceptance, 

 is not thus to be so easily overthrow^ especially 

 until some more satisfactory and fruitful alter- 

 native hypothesis shall have been put forward to 

 take its place. 



Heydenweiller, studying chemical actions of a 

 very mild order, such as the solution of copper 

 sulfate in water and the substitution of iron 

 for copper sulfate the changes being conducted 

 in a closed vessel observed that the chemical 

 action was accompanied by a real but minute 

 alteration in w r eight. In a notice of Heydenweil- 

 ler's work, Lord Rayleigh mentions the question 

 that arises whether the mass changes as well as 

 the \veight. If it does, and it should prove that 

 the btal amount of matter involved in a chemical 

 change is not a fully constant quantity, then im- 

 portant revisions will have to be made in physical 

 science, and some facts that are now puzzling 

 may be explained. If, on the other hand, the 

 mass too does not change, and it is shown that 

 mass and weight are not always in strict propor- 

 tion, the accuracy of certain mechanical construc- 

 tions in which mass and weight are important fac- 

 tors will be affected. 



In a paper on zymic action read before the 

 chemical section in the British Association, Prof. 

 Adrian Brown cited the experimental results of 

 an investigation of the action of invertose on 

 cane-sugar. They confirm the conclusions of pre- 

 vious workers that the action of inversion does 

 not follow r the simple law of mass action. But 

 the author does not regard the action as independ 

 ent of mass influence. He considers that mass 

 influence in inversion changes is restricted by 

 some other and hitherto unrecognized influence, 

 which he believes he has found in the time factor 

 of molecular change. 



It was shown in a paper read by G. T. Bailey in 

 the British Association that microscopic exami- 

 nation had revealed that metals occur in two 

 forms, viz., as (a) minute scales or spicules, and 

 as (&) a transparent glass-like substance. The 

 spicules do not vary much in size in the different 

 metals, and have a diameter of from y^nr to T^J 

 of a millimeter. The form (a) passes into the 

 form (6) when the metal is pressed or hammered, 

 and all polished metallic surfaces are covered with 

 a thin layer of this transparent form as with a 

 lacquer enamel. 



Chemical Physics. Prof. James Dewar de- 

 tailed some of the results of his researches in ex- 

 tremely low temperatures in a Bakerian lecture 

 on The Nadir of Temperature and Some Allied 

 Problems, delivered before the Royal Society. He 

 had found that the helium thermometer, which 

 records 5 F. absolute as the boiling-point of 

 hydrogen, gives 16 F. absolute as the melting-, 

 point. This value does not differ greatly -from the 

 value previously deduced from the use of hydro- 

 gen-gas thermometers, 16.7. The lowest tem- 

 perature recorded by gas thermometry is 14.5 

 absolute, but with more complete isolation and a 

 lower pressure of exhaustion it will be possible 

 to reach 13 F. absolute, which is the lowest tem- 

 perature that can be commanded by the use of 

 solid hydrogen. The latent heat of liquid hydro- 

 gen near the boiling-point is about 200 units, 

 and the latent heat of solid hydrogen is about 

 16 units. 



The order of the specific heat of liquid hydrogen 

 was determined by the author as averaging 

 about (5 between the freezing-point and boiling- 



