Oct. 2, I 



NA TURE 



55i 



result of these experiments it is shown that, when a mixture of 

 dry carbonic oxide and hydrogen is exploded with oxygen in- 

 sufficient for complete combustion, at a temperature at which no 

 condensation of steam can take place during the reaction, and at 

 a temperature greater than the critical pressure, an equilibrium 

 between two opposite chemical changes is established which is 

 independent of the mass of oxygen taken, so long as this quantity 

 is less than half the hydrogen. Within these limits the law of 

 mass is completely verified for the gaseous system composed of 

 carbonic oxide, carbonic acid, hydrogen, and steam at a high 

 temperature. 



On Magnetic Rotation of Compounds in Relation to their 

 Chemical Composition, by W. H. Perkin, Ph.D., F.R.S.— The 

 author gave a resume of his researches on the magnetic rotary 

 polarisation of compounds in relation to their chemical compo- 

 sition. After referring to the remarkable discovery of Faraday 

 in relation to this subject, and the results obtained by more 

 recent workers in this field, it was shown that no relationship 

 in reference to chemical composition was likely to be found by 

 the usual method of calculating the results of the observation of 

 unit-lengths of the fluid bodies examined, but that, if lengths 

 related to each other in proportion to their molecular weights — 

 making the necessary correction for the difference of densities 

 — were compared, a useful result would probably be obtained. 

 Experiments have proved this to be the case ; and in the series 

 of homologous compounds it was found that for every addition 

 of CH, a definite increase of what is called the "molecular 

 rotation " is obtained. Besides this it was found that the rota- 

 tion also was capable of indicating differences in the construc- 

 tion of organic compounds. Iso, secondary, tertiary bodies 

 give different results from the normal compounds. The com- 

 pounds containing the halogens were also referred to, and for- 

 mulas given by which the molecular rotation of twenty-six series 

 of compounds could be calculated. 



Spectroscopic Studies of Explosions, by Profs. Liveing and 

 Dewar. — The explosions observed were chiefly those of hydro- 

 gen and oxygen and of carbonic oxide and oxygen, and were 

 made in an iron tube fitted with quartz ends. The spectra were 

 both observe. 1 with the eye and photographed. Linings of thin 

 sheet metal of various kinds were introduced into the tube. 

 The metals iron, nickel, and cobalt gave many lines in the 

 flash. No other metal gave anything like so many lines as 

 these three, but magnesium gave the /' group, copper gave one 

 green and two ultra-violet lines, manganese the violet triplet, 

 and chromium three triplets. On the other hand, zinc, cad- 

 mium, mercury, aluminium, bismuth, antimony, and arsenic 

 developed no lines in the flash. It appears to be proved that 

 iron, nickel, and cobalt are volatile in some degree at 3000°. It 

 might be possible to establish a spectroscopic scale of tempera- 

 ture if the lines successively developed with increasing tempera- 

 ture were noted. Thus, the iron line T seems to be just deve- 

 loped at 3000', the aluminium lines at II at a somewhat higher 

 temperature, the lithium blue line may be just seen in the inner 

 green cone of a Bunsen burner, while the green line comes out 

 in the explosion fla h. [The photographs of the explosion spectra 

 were exhibited to the Section.] 



On Evaporation and Dissociation, by Prof. William Ramsay 

 and S. Young, D. Sc. — The authors described experiments made 

 with the object of ascertaining whether the coincidence of the 

 curves which represent the vapour-pressures of stable solid and 

 liquid substances at different temperatures with those indicating 

 the maximum temperatures attainable by the same substances at 

 different pressures, when evaporating with a free surface, holds 

 good also for substances which dissociate in their passage to the 

 gaseous state. The substances examined were chloral hydrate, 

 ammonium carbamate, phthalic acid, succinic acid, aldehyde 

 ammonia, ammonium chloride, nitric peroxide, and acetic acid. 

 It was found that, with chloral hydrate and ammonium car- 

 bamate, which cannot exist at all in the gaseous state, the tem- 

 peratures of volatilisation do not form a curve. When the 

 dissociation was considerable, but not complete, as in the case 

 of phthalic and succinic acids, an indication of a curve was 

 observed at low pressures, but it differed widely both in form and 

 position from that representing the vapour-pressures or pressures 

 of dissociation. As the dissociation increases the curves approach 

 each other more closely, and they appear to be coincident in the 

 case of ammonium chloride and nitric peroxide within the limits 

 of temperature at which observations were made, and at which 

 the amount of dissociation is probably small. With acetic acid 

 very numerous observations proved the perfect coincidence of 



the curves. The results appear to be unfavourable to the view 

 that, when liquefaction of a stable substance takes place, gaseous 

 molecules coalesce to form more complex groups of molecules, 

 and that these complex molecules dissociate when the substance 

 is vaporised. 



A Redetermination of the Atomic Weight of Cerium, by H. 

 Robinson, B.A. Cambridge. — Cerous chloride was prepared 

 by passing hydrochloric acid over cerium oxalate at first gently 

 heated and afterwards raised to redness. The solution of pure 

 chloride was added to a pure solution of silver nitrate, and then 

 dilute solution of silver nitrate was added from a weighed bulb, 

 until the precipitation of chlorine was complete. The liquids 

 were illuminated by yellow light only during the precipitation. 

 As a mean of seven closely concordant results, the atomic weight 

 of cerium is given as I40'2593, that of silver being 107 '93. 



The Action of Sulphuretted Hydrogen on Silver, by Prof. F. 

 P. Dunnington, University of Virginia. — A piece of pure silver, 

 flattened and carefully polished on each face, was placed in 

 the middle of a glass tube two feet long. At each end of the 

 tube a plug of five inches of phosphoric anhydride was confined 

 by glass wool. Pure dry hydrogen was passed through this 

 tube while it was gently heated throughout. The hydrogen was 

 then removed by a Sprengel pump, the silver being heated to 

 300° C. This operation was repeated three times, and then 

 pure dry sulphuretted hydrogen was slowly passed through the 

 apparatus for an hour, and the tube finally drawn off at each 

 end. After a few days the silver was slightly darkened near its 

 edges, and after five months the silver was blackened on its edges, 

 while the main portion of the surface was white and bright. [The 

 silver was exhibited to the Section in this state.] 



On Molecular Volumes, by Prof. W. Ramsay. — The object of 

 this research was to ascertain whether, as has long been taken 

 for granted, the boiling-point of compounds under equal pres- 

 sures really afforded suitable points for a comparison of their 

 molecular volumes. The experiments made with the following 

 series of compounds — water, methyl alcohol, ethyl alcohol, 

 propyl alcohol, isopropyl alcohol, isobutyl alcohol, and ether — 

 prove that the value of the group CH, is by no means constant. 

 (1) While at the boiling-points of these liquids at low pressures 

 the value is approximately constant (fluctuating between 17 '5 

 and 22), at high temperatures the difference becomes much more 

 marked, attaining at 20 m. of mercury pressure the greatest 

 irregularity ; e.g. the difference between the molecular volumes 

 of ether and isobutyl alcohol, two isomeric substances, amounts 

 to a total of twenty units. (2) It was found by experiment that 

 when the liquids were at temperatures corresponding to equal 

 vapour-pressure, but exposed to their critical pressures, no corre- 

 spondence between their molecular volumes was observable. 

 (3) It was thought possible that if the liquids, still at tempera- 

 tures corresponding to equal vapour-pressure, could have existed 

 under no pressure, some basis of comparison might be found. 

 From the known compressibility of the liquids it was possible 

 to calculate their volume in this hypothetical state. Although 

 by this method their relative volumes were considerably altered, 

 yet no point of co nparison was reached. (4) The author there- 

 fore concludes that the boiling-points of liquids, under whatever 

 pressure they may be taken, are not suitable temperatures at 

 which to compare their molecular volumes. 



On Some Phenomena of Solution, Illustrated by the Case of 

 Sodium Sulphate, by Prof. W. A. Tilden, F.R.S.— The study 

 of the solubility of sodium sulphate in water at temperatures 

 above ioo° C, leads to the conclusion that the salt dissolves in 

 the anhydrous state. In order to determine whether this salt 

 dissolves in water at lower temperatures in the anhydrous or lite 

 hydrated state, the author has made a series of calorimetric 

 measurements of the thermal changes which attend the act of 

 solution of Na. 2 S0 4 in water at temperatures below and above 

 33° to 34°, the critical point in the curve of solubility. 



Calorimetric Effect of Dissolving Na„So i in n Molecules 

 of Water at T° " 



IOO 



100 



IOO 

 IOO 

 100 



T° 



317 

 35-4 

 42-85 



46 I 



55-0 



1740 



1522 



1342 



1071 



985 



These figures establish the fact that by dissolving anhydrous 

 sodium sulphate in water at temperatures above 33 , the thermal 

 change is still positive, although a diminishing quantity, and 



