November 15, 1894J 



NATURE 



71 



SOCIETIES AND ACADEMIES. 



London. 



Physical Society, October 26. — Prof. A. W. RUcker, F. R. S. , 

 President, in the chair. — The meeting was held in the rooms of 

 I the Chemical Society, Burlington House. — In opening the pro- 

 ceedings the President said the occasion might be regarded as 

 another sign that the boundary between Chemistry and Physics 

 was breaking down. On behalf of the Council he tendered the 

 I thanks of the Physical .Society to the Chemical Society for the 

 1 use of the rooms. — Prof. H E. Armstrong, President of the 

 \ Chemical Society, said his Council offered a cordial welcome to 

 ', the Physical Society. The change, he thought would prove of 

 much greater importance than a mere removal. Now that the 

 childhood of the Physical Society was passed, its manhood 

 involved new responsibilities, and great opportunities for good 

 presented themselves. The Physical Society of London 

 ought now to become the head-centre of physics in the United 

 Kingdom. He (Dr. Armstrong) was pleased to learn that the 

 Society had undertaken the preparation and publication of 

 abstracts of physical papers appearing in foreign periodicals, and 

 said the matter was of such great importance that it should be 

 done thoroughly. In a work of such a magnitude, he regarded 

 the co-operation of other societies, such as the Institution of 

 Electrical Engineers, as absolutely necessary. — The President, in 

 acknowledging the welcome, said the Physical Society was 

 extremely obliged to the President and Council of the Chemical 

 Society for the great benefits conferred. Dr. .Armstrong's 

 ailvice to go ahead would not be forgotten. He then announced 

 that at future meetings tea would be provided for members at 

 4. 50. — The exhibition of a voltameter by Mr. Naber was post- 

 jjiined. — Mr. E. H. Griffiths .read a paper on the influence of 

 temperature on the specific heat of aniline. After pointing 

 out that most observations of specific heat depend on water, 

 whose capacity for heat varies considerably with temperature, 

 the author said large differences existed between the values 

 obtained by different observers as the latent heats of evaporation 

 of water and other liquids, and these differences were probably 

 due to the variability of the water standard, which had been 

 erroneously assumed constant. Precise measurements in calori- 

 metry were of such great importance that the exact relation 

 between the capacity for heat of water and its temperature 

 should be completely determined. With apparatus such as he 

 had used with aniline, this could be done in six months, pro- 

 vided someone could be found who could devote his whole time 

 to the subject. The results of his own experiments were ex- 

 ))ressed in terms of the capacity for heat of water at 15' C. (at 

 which J = 4'I98 X lo'" ergs.), and hence were referred to 

 a definite standard. A great desideratum in calorimetric 

 work was a calorimeter whose ^surroundings could be kept 

 at a very -constant temperature. This he had obtained by 

 using a tank holding about 20 gallons of water, in which 

 a steel ve^sel, shaped like a hat-box with lioilow sides and 

 bottom, was immersed. The cavity w.is filled with about 70 

 pounds of mercury, and served as the bulb of a thermometer ; a 

 nilie communicating with this bulb acted as a regulator to 

 Liiutrol the gas supply which healed the water in the lank. 

 The tank water was circulated rapidly by a screw-propeller. 

 L'nder ordinary conditions the temperature of the outside of the 

 steel chamber could be kept constant within i/ioo" C. The 

 calorimeter itself was of brass, and suspended by glass tubes 

 from the lid of the steel chamber. A stirrer worked by an 

 electromotor kept the contents in rapid motion. In the experi- 

 ments on aniline, heat was supplied to the liquid in the interior 

 by maintaining known potential differences (equal to some 

 multiple of the E. M.F. of a Clark's cell) between the ends of a 

 coil of German silver wire placed inside. The rate of rise of 

 temperature of the inside over the outside was measured by 

 platinum thermometers, one of which was placed in the 

 calorimeter, and the other embedded in the walls of the 

 steel vessel surrounding the calorimeter. By this means differ- 

 ences in temperature of i/iooo of r C. could be detected with 

 certainty. A special method of adjusting the potential differ- 

 ence between the ends of the German silver wire was employed, 

 by which the constancy could be maintained within i part in 

 I0,ooo. To minimise corrections arising from heat generated 

 by stirring the liquid, and that lost by radiation, &c., from the 

 calorimeter, the ex[>eriments were made about temperatures at 

 which these corrections balanced each other ; the rise of tem- 

 perature was then due to the electric supply alone. The 



specific heat, S, of the liquid at temperature flj could then be 

 determined from the formula 



dt JRj(SiM + a/i) 



where — i = rate of rise of temperature at temperature flj 



J = mechanical equivalent of heat, 

 E = potential difference between the ends of the coil, 

 R] = resistance of the coil, 

 M = mass of liquid, 

 and u\ = water equivalent of calorimeter at temperature 9;. 



Experiments were made with different values of E, and two 

 widely different masses of liquid were used. The author was 

 thus enabled to find S, without knowing vi^. Having found 

 S,, the water equivalent of the calorimeter could then be 

 determined. Many important details of construction and 

 manipulation of the apparatus, as well as the method employed 

 in reducing the results, are given in the paper. The final values 

 (or Si and w^ at several temperatures are given below. 



Specific heat of Water etjtiivalent of 



.iniline. calorimeter. 



0-5137 79'82 



Temperaturt. 



is°c. .. 



20 o'SiSS So-ii 



30 o'5i98 8o'9o 



40 o'S244 S2-I9 



50 05294 83-39 



The aniline employed was supplied by Messrs. Harrington 

 Bros, as "pure colourless," but had initially a light brown 

 tinge. After being in use some time, the colour had darkened 

 considerably, but its specific heat had not sensibly changed. 

 Recently he had tried a hydrocarbon liquid which promised to 

 be still more satisfactory as a standard liquid in calorimetry. 

 In the course of his remarks the author said a name for 

 "capacity of heat per unit volume" was greatly needed, and 

 invited suggestions. Dr. Armstrong thought the author had 

 made a particularly happy selection in aniline, for it could now 

 be obtained in any quantity absolutely pure. When pure it did 

 not discolour on exposure, and would probably be very satis- 

 factory as a standard liquid. He doubted whether any hydro- 

 carbon could be better. Prof. Ayrton congratulated the author 

 on the extreme accuracy (obtained. Recently he had arranged 

 an experiment for determining the mechanical equivalent of heat 

 by the electrical method, which gave very accurate results 

 without any corrections whatever being necessary. Prof. S. P. 

 Thompson thought the whole phraseology of specific heat 

 required revising. Prof. Perry agreed with Mr. Griffiths that a 

 name for "capacity for heat per unit volume" was greatly 

 needed, and Mr. Lucas suggested "heat density," but this was 

 not satisfactory. Dr. Sumpnersaid most text-books on physics 

 attribuledithe advantage of the mercury thermometer to the low 

 specific heat of mercury, whereas the capacity for heat per unit 

 volume was the important factor. Mr. Watson inquired to 

 what temperature the alloy which the author had used lo connect 

 glass to metal had been tested? The President said the paper 

 was of great impDrtance because it dwelt with the application 

 of electrical methods to thermometry. The mercury thermo- 

 meter had been quite superseded for work such as had just been 

 described. Mr. Griffiths, in reply to Mr. Watson, said the alloy 

 had been used successfully between 10° and 62" C. It gave 

 way at 71° C. lie was glad to learn from Dr. .\rmstrong that 

 aniline could now be got ))ure. Prof. Ramsay had written to 

 say he did not think the slight impurities in ordinary aniline 

 would have much effect on its specific heat. Mr. Blakesley 

 asked if aniline could be taken as pure if it did not change 

 colour on exposure. Dr. -Armstrong, in reply, said yes, if the 

 boiling point was also constant. 



Paris. 

 Academy of Sciences, November 5. — M. Loewy in the 

 chair. — On an apparatus serving to demonstrate certain con- 

 sequences of the theorem of areas, by M. Marcel Deprez. This 

 is an apparatus designed to show that a body passing freely 

 through s| ace may rot.ate on its own .axis without suffering the 

 application of any exterior force, such rotation being produced 

 by interior movements of parts of its system. — On the theorem 

 of areas, by XL P. AppcU. — On the theory of flow for a weir 

 with depressed or partly submerged liquid sheet, in the case 

 where a horizontal armature gives the inferior maximum con- 

 traction, by M.J. Boussinesq. — On the vaporisation of carbon, 

 by M. Henri Moissan. The heatof the electric furnace enables 



NO. 1307, VOL, 51] 



