46 



NATURE 



\_May 



iSSo 



cephalopoda of the north-eastern coast of America, by A. E. 

 Verrill. — Notices of recent American earthquakes, by C. J. 

 Rockwood, jun. — Observations on the height of land and sea- 

 breeze=, taken at Coney Island, by O. T. Sherman. — New 

 method of spectrum observation, by J. N. Lockyer. — Presenta- 

 tion of sonorous vibrations by means of a revolving lantern, by 

 H. Carmichael. — Chemical composition of childrenite, by J. L. 

 Penfield.— Ob.-ervations on the planet Lila;a, by C. H. F. 

 Peters. — Efficiency of Edison's electric light, by II. A. Rowland 

 and G. F. Barker. 



Aitnalen der Physik nnd Chemie, No. 3. — On the behaviour 

 of carbonic acid in relation to pressure, volume, and temperature, 

 by R. Clausius. — On a relation between pressure, temperature, 

 and density of saturated vapours of water and some other liquids 

 (continued), by A. Winkelmann. — Researches on the vibrations 

 of a normal tuning-fork, by R. Koenig. — Researches on the equi- 

 potential distriliution of the magnetic fluids of cylindrical steel 

 bars, by W. Schaper. — General theory of the deadening influence 

 of a multiplier on a magnet (continued), by K. Schering. — On 

 ultra-violet rays, by J. L. Schonn. — On a spectrotelescope, by 

 P. Glan. — On a new simple mode of streak observation, by V. 

 Dvorak. — Contribution to a history of the mechanical theory of 

 heat, by E. Oedier. 



yournal ds Physlijue, April. — On the measurement of wave- 

 lengths of infra-red radiations, by M. Mouton. — Solar spots and 

 protuberances observed «ith a spectroscope having great dis- 

 persion, by M. ThoUon. — Measurement of the electromotive 

 force of contact of metals by the Peltier phenomenon, by M. 

 Pellat. — Description and use of the telescope and scale of Edel- 

 mann, by M. Terquem. 



yournal of the Franklin Institute, April. — Naval architecture, 

 by Mr. Haswell. — Saws, by Dr. Grimshaw. — Engraving, by 

 Mr. Sartain. — On D'Auria's engine-governor and the action of 

 governors in general, by Prof. D'Auria. — A new hypothesis 

 regarding comets and temporary stars, by Prof. Tobin. 



Rivisla Sciintifico-Industriale, No. 6, March 31. — On a case 

 of permanent polarity of steel opposite to that of the magnetising 

 helix which produces it, by Prof. Righi. — Reflexions on an 

 experimental and fundamental principle in hydrostatics, by Prof. 

 Cantoni. — On Elban topaz, by S. Corsi. 



No. 7, April 15. — Radiant matter and the theory of Crookes, 

 by S. Piazzoli. — Pliocene fossils of the yellow sand found in the 

 neighbourhood of Vignc, Schifanoia, and Montoro (Narni), w ith 

 a suggestion as to the subapennine formation of these three 

 places, by S. Terrenzi. 



Reale Istituto Lombardo di Scieiitc e Lettere. Rendiconti, vol. 

 xiii. fasc. iii. — On Garovaglineae, a new tribe of Collemacea;, by 

 S. Trevisan. — Comparison of the winter 1879-80 with the pre- 

 ceding one in Mdan, by Prof. Hajech. — Diurnal oscillatior.s of 

 the declination-needle, in 1879, at the Brera Observatory, Milan, 

 by Prof. Schiaparelli. — Transfusion of blood into the peritoneum 

 in an oligocitemic lunatic ; effects on the circulation of blood and 

 on the general state of the patient, by Profs. Golgi and Raggi. — 

 The nephod<jscope, an instrument for determining the direction 

 of motion of clouds, by Prof. Fomiori. 



SOCIETIES AND ACADEMIES 

 London 



Roj al Society, April 22.— " On the Critical State of Gases." 

 By William Ramsay, Ph.D., Professor of Chemistry in Univer- 

 sity College, iiristul. 



It is well known that at temperatures above that which pro- 

 duces what is termed by Dr. Andrews the "critical point" of a 

 liquid, the substance is supposed to exist in a peculiar condition, 

 and Dr. Andrews purposely abstained from speculating on the 

 nature of the matter, whether it be liquid or gaseous, or in an 

 intermediate condition, to which no name has been given. As 

 my observations bear directly on this point, it may be advisable 

 first to describe the experiments I have made, and then to draw 

 the deductions which appear to follow from them. 



A piece of baioaieter tubing about three inches long was 

 sealed at one end and drawn into a capillary tube at the other ; 

 after being filled with methyl formate it was exhausted, and 

 after two-thirds of the ether had evaporated was sealed. By 

 this means all air was removed from the tube, which contained 

 merely the ether and its vapour. 



I. On applying heat the temperature gradually rose to 22i'''5 



(coiT.) ; daring the rise the meni-cus of the liquid gradually 1 

 became less curved, and at the above-mentioned temperature 

 disappeared. On cooling to 2iS° a mi.-t was seen at the point 

 where the meniscus had disappeared, and the meniscus shortly 

 afterwards became again visible. 



2. Two similar tubes were prepared, one containing less and 

 the other more of the same ether ; the point at which the 

 meniscus disappeared in the former was 228°, and in the latter 

 2I5°- 



3. A tube of the shape shown was filled to the mark with 

 methyl formate and heated in an inclined position, the portion 

 containing the liquid being the lower. The liquid, as usual, 

 expanded, and at the moment when the meniscus disa]ipeared it 

 nearly filled the lower half. The source of heat was then with- 

 drawn, and ou cooling the liquid all condensed in the lower ) 

 half. 



4. The last experiment was varied by tilting the tube after the 

 meniscus of the liquid had disappeared, so that that half which 

 had contained the liquid w as uppermost. On cooling, the Hquid 

 condensed in the uj^per half of the tube. 



5. The experiment was again varied by keeping the tube at a 

 temperature a few degrees above the point where the meniscus 

 vanished, for half an hour. On cooling, an almost equal quan- 

 tity had condensed in each division of the tube. (During Ex- 

 periments 3, 4, and S. great care must be taken to keep the 

 heater from draughts of cold air, otherwise unequal cooling 

 restdts and distillation takes place.) 



6. It was noticed that that half of the tube containing liquid, 

 after the meniscns had vanished, appeared _/;(//, while the other 

 half of the tube seemed to be itnply. The refractive indices of 

 the fluid contained in the tubes \a ere therefore different. The 

 portion of the tube containing liquid was shown to be a more 

 poH erful cylindrical lens than the empty portion, for on focussing 

 a spot behind the tube h ith a microscope, the focus was shorter 

 when the portion which had contained liquid was placed between 

 the microscope and the spot than when the portion appearing 

 empty was interposed. 



7. From experiments on the expansion of liquids above their 

 boiling-points, of which numerical details shall be given on a 

 future occasion, it appears probable that the .specific gravity of 

 the hot liquid, at the temperature at which the meniscus vanishes, 

 is identical with that of the compressed gas evolved from the 

 liquid. This has also been noticed by Ansdell in two cases, viz., 

 hydrogen chloride and acetylene. ' 



8. From observations on the expansions of liquids at high '■ 

 temperatures it has been pioved that liquids above the tem- 

 peratures at which their menisci vanish are not uniformly 

 compressible. 



From these observations I would draw the following infer- 

 ences : — When a liquid is heated under pressure it expands, and 

 at the same time evolves vapour. The vapour gains in specific 

 gravity, while the specific gravity of the liquid is rapidly dimi- 

 nishing. T/ie cri'ical point is that point at which the liquid, 

 o'ning to expansion, and the gas, ott'ing to compression, acquire 

 the same specific gravity, and consequently mix with one another. 

 From the first experiment it is seen that, on cooling, the liquid 

 contracts more rapidly than the gas, and consequently separates 

 as a mist through the whole of the tube, and, from its gravity, 

 separates at the lower half. The second experimevit shows that 

 when the tube contains a small amount of liquid the space left 

 for gas is larger, and consequently more vapour must be given 

 off by the liquid before enough gas can be compressed till it 

 acquires the same specific gravity as the liquid ; the temperature 

 at which the meniscus disappears is consequently higher. If the 

 space left for gas be smaller, the opposite is the case. The 

 fourth, fifth, sixth, and seventh experiments demonstrate that by 

 suitable means it is possible to prevent, or rather to retard, 

 the mixing of gas and liquid. They then retain their several 

 refractive indices. If, however, time be allowed for diffusion 

 through the capillary tube, the whole becomes homogeneous, and 

 the refractive indices of the fluids contained in either portion cf 

 the tube are then identical. 



So long as gas is being compressed, pressure rises gradually 

 with decrease of volume, whereas, even above their critical 

 points, liquids are comparatively incompressible. 



In conclusion, let me refer to a paper communicated to tlie 

 Society by Messrs. Hannay and Hogarth last October, entitled 

 " On the Solubility of Solids in Gases." Should the views of 

 the subject suggested by the above experiments be correct, it 

 follows that these gentlemen have observed nothing unusual, but 



