214 



NA TURE 



[July i, 1897 



Ethane from ethyl iodide is not very pure, it has generally 

 several per cent, of an admixture of a substance of higher critical 

 temijerature and higher density than ethane ; this substance is 

 probably butane. Ethane from sodic acetate, by electrolysis, is 

 nearly pure ; the method of preparation is described by the author. 

 The pressure and corresponding volumes during condensation 

 are given for this substance at various temperatures. In the 

 foruier paper, above referred to, instances are mentioned of 

 mixtures having critical temperatures /^eow those of the com- 

 ponent substances. The only instance of critical temperatures 

 above those of the components, seem to be those relating to 

 mixtures of carbonic acid and acetylene. According to an ex- 

 periment of Dewar's, however, a mixture of ^COj and ^CoH.^ 

 has a critical temperature of 41° C, those for carbonic acid and 

 acetylene being 31° and 37° respectively. The present investi- 

 gation contradicts this result. Dewar may not have taken 

 sufficient precaution in avoiding errors of retardation. Mixtures 

 of carbonic acid and acetylene have critical temperatures between 

 those of the component pure gases. The diagram connecting 

 temperature and volume shows that the plait-point curve is a 

 line with small curvature ; the border-curve is relatively 

 narrow. An instance of a critical temperature above those of 

 the components, for this mixture, has not yet been proved. 

 Theory indicates that this phenomenon probably occurs for 

 mixtures having a minimum vapour-pressure at low temperature. 

 Critical temperatures below those of components, seem to occur 

 for mixtures having a maximum vapour-pressure ; as for nitrous 

 oxide and ethane. The law connecting the two phenomena is 

 deduced from van der Waal's theory. As a further application 

 of this theory, it is shown that in consequence of certain co- 

 incidences between the real border-curve and the hypothethical 

 border-curve, the critical point of the maximum mixture may be 

 determined in exactly the same way as for a single substance. 

 A remark is added with regard to the condensation of such 

 substances as exhibit changes of molecular systems. If an 

 association takes place of molecules to more complicated 

 systems, van der Waal's formula does not apply. Dr. S. P. 

 Thompson asked whether diagrams characteristic of cyanogen 

 had been obtained. Its remarkable polymerism suggested an 

 interesting case for critical phenomena. Dr. Kuenen thought 

 such a substance might be worth investigation. — A paper by 

 Dr. Barton, on the attenuation of electric waves in wires, was 

 taken as read.— Mr. G. F. C. Searle read a paper on the steady 

 motion of an electrified ellipsoid. The first part of the investi- 

 gation is printed in the PhiL Trans. Roy. Soc. ; it contains the 

 principles required in the solution of problems with respect to 

 moving electrical charges. The second part, now presented to 

 the Physical Society, deals with the motion of a charged 

 ellipsoid ; the treatment is entirely mathematical. When any 

 system of electric charges moves with uniform velocity through 

 the oether, the electro-magnetic field, referred to axes moving 

 forward with the charges, can be completely defined by means 

 of a quantity of which the electric force and the magnetic 

 force are simple functions. Another vector concerned in the 

 problem is the mechanical force experienced by a unit charge 

 moving with the rest of the system. A distribution of 

 electricity on the surface of a charged body such as to 

 give zero distribution at all points inside the surface is an 

 equilibrium distribution. Since the mechanical force vanishes 

 inside the surface, it is shown that on the outside of the surface 

 the mechanical force is perpendicular to the surface, and the 

 above-mentioned function is constant over the surface, and the 

 distribution on an ellipsoid is the same for motion as for rest. 

 When a charged sphere is at rest it produces the same effect as 

 a point-charge at its centre. If the sphere is in motion it pro- 

 duces the same effect as a uniformly-charged line whose length 

 bears to the diameter of the sphere the same ratio as the velocity 

 of the sphere bears to the velocity of light. When the sphere 

 moves with the velocity of light, the line becomes the diameter 

 of the sphere ; the same is true for an ellipsoid. At the velocity 

 of light, the charge on any surface is in equilibrium, whatever 

 the distribution. The force between two charges moving with 

 the speed of light, is zero. The lines of electric force for a 

 charged sphere in motion are not radial ; they form a series of 

 hyperbolas. The author proceeds to calculate the total energy 

 possessed by an ellipsoid when in motion along its axis of 

 figure. Expressions are given (l) for the energy of a Heaviside 

 ellipsoid ; (2) for a sphere ; and (3) for a very slender ellipsoid. 

 In all cases the energy becomes infinite when the charges move 

 at the velocity of light. It would seem impossible to make 



NO. 1444, VOL. 56] 



a charged body move at a greater speed than that of light. 

 Prof. Perry said the paper would help to solve many problems 

 connected with the effect of the rotation of the earth upon 

 electrical surface charges. An expression might be found for 

 the mechanical and magnetic forces due to the motion of a 

 charge at any point of the earth's surface. At the equator a 

 point moves at different velocity at midday to its midnight 

 velocity ; it may now be possible to determine the magnetic and 

 mechanical effects due to electrical charges at equatorial points. 

 Mr. Blakesley asked whether, in calculating the mutual action 

 of two charged particles, proceeding at the velocity of light, it 

 was assumed that the lines of motion were parallel. Mr. 

 Searle said he had always considered parallel lines of motion ; 

 he could not say whether the force would be zero in any other 

 case. The results arrived at in the paper could be applied to 

 problems connected with distributions of terrestrial charges. — 

 The President proposed votes of thanks to the authors ; the 

 meeting then adjourned until November. 



Chemical Society, June 3.— Prof. Dewar, President, in the 

 chair. — The following papers were read : — On the thermal phe- 

 nomena attending the change of rotatory power of freshly-pre- 

 pared solutions of certain carbohydrates ; with some remarks on 

 the cause of multirotation, by H. T. Brown and S. Pickering. 

 Freshly prepared solutions of dextrose, Isevulose, and milk-sugar 

 contain the sugar as an unstable o-modification, which gradually 

 changes into a stable ^-modification ; this change is made 

 apparent by a change of specific rotation, and, as the authors 

 show, is accompanied by evolution of heat, the quantity of 

 which has been measured. — On the ihermo-chemistry of carbo- 

 hydrate-hydrolysis : (i) The hydrolysis of starch by vegetable 

 and animal diastase ; (2) the hydrolysis of cane-sugar by in- 

 vertase, by H. T. Brown and S. Pickering. The authors have 

 determined by direct measurement the heat evolved in the hydro- 

 lysis of starch by malt-diastase, pancreatic-diastase, Taka-dias- 

 tase and saliva, and in the hydrolysis of cane-sugar by invertase. 

 — Optical inversion of camphor, by F. S. Kipping and W. J. 

 Pope. It is shown that during the sulphonation of ^-camphor, 

 part of it is converted into /-camphor. — Derivatives of cam- 

 phoric acid. Part ii. Optically-inactive derivatives, by F. S. 

 Kipping and W. J. Pope. — Racemism and pseudoracemism, by 

 F. S. Kipping and W. J. Pope. The authors show that a 

 number of apparently racemic compounds really consist of inter- 

 calations of crystals of the two enantiomorphously related com- 

 ponents ; the term pseudoracemic is applied to such substances 

 of which several are described in detail. — Note on some new 

 gold salts of the Solanaceous alkaloids, by H. A. D. Jowett. 

 Hyoscine hydrobromide combines with auric chloride and 

 bromide, giving salts of the composition X, HBr, AUCI3 and 

 X, HBr, AuBrg. — Production of camphenol from camphor, by 

 J. E. Marsh and J. A. Gardner. Camphenol, an isomeride of 

 camphor, is obtained by the action of strong sulphuric acid on 

 chlorocamphene, camphene dichloride, and turpentine dihydro- 

 chloride. — Preliminary note on the oxidation of fenchene, by J. 

 A. Gardner and G. B. Cockburn. Cis-camphopyric acid is pro- 

 duced on oxidising fenchene with dilute nitric acid. — Apiin and 

 apigenin, by A. G. Perkin. The author produces experimental 

 evidence which renders it probable that apigenin is a hydroxy- 

 derivative of chrysin, the colouring matter of poplar buds. — 

 Rhamnazin, by A. G. Perkin and H. W. Martin.— Experi- 

 mental verification of van 't Hoff's constant in very dilute solu- 

 tion, by M. Wildermann. — The isomeric dibromoethylenes, by 

 T. Gray. The author has been unsuccessful in his attempts to 

 prepare a stereo- isomeride of ordinary symmetrical dibromo- 

 ethylene ; he considers the latter to be the trans-compound. 



Entomological Society, June 2.— Mr. R. Trimen, F.R.S., 

 President, in the chair.— The President referred to the great 

 loss which the Society had sustained by the death of Dr. Fritz 

 Miiller, one of its Honorary Fellows, and to his distinguished 

 services in the cause of entomological science, and especially in 

 forwarding the theory of the origin of species. — Dr. Chapman 

 exhibited the larva of Eriocephala allionella.—Mx. Jacoby ex- 

 hibited a fine example of the large Hepialid, Leto vemis, from 

 Plettenberg Bay, South Africa. The President said that the 

 insect afforded an interesting case of localised distribution, being 

 confined to an area of about fifty by fourteen miles, whereas the 

 larva fed in the wood of Virgilia capensis, a common and widely- 

 distributed leguminous tree. The insect was very conspicuous, 

 and could not have been overlooked in other localities. — Mr. 

 Burr showed a pair of gynandromorphous earwigs, Chelisoches 



