May 31, 1888] 



NATURE 



117 



Mr. Percy Groom, B. A., late of Trinity College, has been 

 elected to the Frank Smart Studentship in Botany at Gonville 

 and Caius College. 



The fittings of the new Chemical Laboratory are costing ,£1000 

 more than was originally estimated (from rough drawings only) 

 by Mr. Lyon, Superintendent of the University workshops. 

 Some of this is due to the fact that the fixing of the tables on a 

 bottom independent of the floors of the rooms, and making the 

 cupboard doors fairly dust-proof, originally recommended, was 

 not adopted till after the tables had been fixed, and much 

 cutting of the floors had to be done. Also much of the iron and 

 steel work was not particularized at first. 



The Council are taking steps to carry out the appropriation of 

 the old Chemical Laboratory to the department of pathology. 



Prof. Darwin will lecture during the long vacation on the 

 theory of the potential, and on attractions, commencing on 

 Tuesday, July io. The lectures will treat principally of gravi- 

 tational problems, including attraction of ellipsoids, Gauss's 

 paper, heat of tin, Jacobi's and Dedekind's ellipsoids, oscilla- 

 tions of a fluid sphere, the foundation of the theory of tides, 

 atmospheres of planets, &c. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, May 3. — " Effect of Chlorine on the Electro- 

 motive Force of a Voltaic Couple." By Dr. G. Gore, F.R. S. 



If the electromotive force of a small voltaic couple of 

 unamalgamated magnesium and platinum in distilled water, is 

 balanced through the coil of a moderately sensitive galvanometer 

 of about 100 ohms resistance, by means of that of a small 

 Daniell's cell, plus that of a sufficient number of couples of iron 

 and German silver of a suitable thermoelectric pile (see Proc. 

 Birm. Philos. Soc., vol. iv. p. 130), the degree of potential 

 being noted ; and sufficiently minute quantities of very dilute 

 chlorine water are then added in succession to the distilled water, 

 the degree of electromotive force of the couple is not affected 

 until a certain definite proportion of chlorine has been added ; 

 the potential then suddenly commences to increase, and continues 

 to do so with each further addition within a certain limit. 

 Instead of making the experiment by adding chlorine water, it 

 may be made by gradually diluting a very weak aqueous 

 solution of chlorine. 



The minimum proportion of chlorine necessary to cause this 

 sudden change of electromotive force is extremely small ; in 

 my experiments it has been 1 part in 17,000 million parts of 

 water, 1 or less than 1/7000 part of that required to yield a 

 barely perceptible opacity in ten times the bulk of a solution of 

 sal-ammoniac by means of nitrate of silver. The quantity of 

 licptid required for acting upon the couple is small, and it would 

 be easy to detect the effect of the above proportion, or of less 

 than one ten-thousand-millionth part of a grain of chlorine, in 

 one-tenth of a cubic centimetre of distilled water by this process. 

 The same kind of action occurs with other electrolytes, but 

 requires larger proportions of dissolved substance. 



As the degree of sensitiveness of the method appears extreme, 

 I add the following remarks. The original solution of washed 

 chlorine in distdled water was prepared in a dark place by the 

 usual method from hydrochloric acid and. manganic oxide, and 

 was kept in an opaque well- stoppered bottle in the dark. The 

 strength of this liquid was found by means of volumetric analysis 

 with a standard solution of argentic nitrate in the usual manner, 

 the accuracy of the silver solution being proved by means of a 

 known weight of pure chloride of sodium. The chlorine liquid 

 contained 2*3 milligrammes or 0-03565 grain of chlorine per cubic 

 centimetre, and was just about three-fourths saturated. 



One-tenth of a cubic centimetre of this solution ( " No. I "), or 

 0003565 grain of chlorine, was added to Q - Q c.c. of distilled water 

 and mixed. One cubic centimetre of this second liquid ("No. 

 2"), oro 0003565 grain of chlorine was added to 99 c.c. of water 

 and mixed; the resulting liquid ("No. 3") contained 

 o 000003565 grain of chlorine per cubic centimetre. To make 

 the solutions (" No. 4 ") for exciting the voltaic couple, successive 

 portions of ^ or ^\ c.c. of ("No. 3") liquid were added to 

 900 cubic centimetres of distilled water and mixed. 



As 1 part of chlorine in 17612 million parts of water had no visible effect, 

 and 1 in 17000 millions had a distinct effect, the influence of the d. (Terence, 

 or of 1 part in 500,000 millions, has been detected. 



I have employed the foregoing method for examining the 

 states and degrees of combination of dissolved substances in 

 electrolytes, and am also investigating its various relations. 



May 17. — "Magnetic Qualities of Nickel." By J. A. Ewing, 

 F. R.S., Professor of Engineering, University College, Dundee, 

 and G. C. Cowan. 



The experiments described in the paper were made with the 

 view of extending to nickel the same lines of inquiry as had 

 been pursued by one of the authors in regard to iron (Phil. 

 Trans., 1885^3.523). Cyclic processes of magnetization have been 

 studied, in which a magnetizing force of about 100 C.G.S. units 

 was applied, removed, reversed, again removed, and re-applied, 

 for the purpose of determining the form of the magnetization 

 curve, the magnetic susceptibility, the ratio of residual to 

 induced magnetism, and the energy dissipated in consequence of 

 hysteresis in the relation of magnetic induction to magnetizing 

 force. Curves are given, to show the chiracter of such cycles 

 foi nickel wire in three conditions : the original hard-drawn 

 state, annealed, and hardened by stretching after being annealed. 

 The effects of stress have also been examined (1) by loading and 

 unloading magnetized nickel wire with weights which produced 

 cyclic variations of longitudinal pull, and (2) by magnetizing 

 while the wire was subjected to a steady pull of greater or less 

 amount. The results confirm and extend Sir William Thomson's 

 observation that longitudinal pull diminishes magnetism in 

 nickel. This diminution is surprisingly great : it occurs with 

 respect to the induced magnetism under both large and small 

 magnetic forces, and also with respect to residual magnetism. 

 The effects of stress are much less complex than in iron, and 

 cyclic variations of stress are attended by much less hysteresis. 

 Curves are given to show the induced and residual magnetism 

 produced by various magnetic forces when the metal was main- 

 tained in one or other of certain assigned states of stress ; also 

 the variations of induced and residual magnetism which were 

 caused by loading and unloading without alteration of the 

 magnetic field. Values of the initial magnetic susceptibility, 

 for very feeble magnetizing forces, are stated, and are cqmpared 

 with the values determined by Lord Rayleigh for iron, and the 

 relation of the initial susceptibility to the stress present is in- 

 vestigated. The paper consists mainly of diagrams in which 

 the results are g<aphically exhibited by means of curves. 



Chemical Society, May 3. — Mr. W. Crookes, F.R. S., in the 

 chair. — The following papers were read : — The determination of 

 the molecular weights of the carbo-hydrates, by Mr. H. T. 

 Brown and Dr. G. H. Morris. The law established by Blagden 

 in 1788, that the lowering of the freezing-point of aqueous solu- 

 tions of inorganic salts is proportional to the weight of substance 

 dissolved in a constant weight of water, was extended by de 

 Coppet in 1871-72, who pointed out that when the lowering of 

 the freezing-point is calculated for a given weight of the sub- 

 stance in 100 grammes of water, the result, which he termed the 

 coefficient of depression, is constant for the same substance, and 

 that the coefficients for different substances bear a simple relation 

 to their molecular weights. Raoult extended the law to organic 

 substances and to other solvents than water, and showed that 

 when certain quantities of the same substance are successively 

 dissolved in a solvent upon which it has no chemical action, 

 there is a progressive lowering of the point of congelation of the 

 solution, and that this lowering is proportional to the weight 

 of the substance dissolved in a constant weight of water. 

 The "coefficient of depression," A — that is, the depression 

 of the point of congelation produced by 1 gramme of the sub- 

 stance in 100 grammes of the solvent — is given by the formula 

 C x y 

 100 



x grammes of the substance dissolved in y grammes of the 

 solvent, and from this value the " molecular depression," T, is 

 calculated by the formula M x A = T, where M is the molecular 

 weight of the substance in question. T is a value varying with 

 the nature of the solvent, but remaining constant with the same 

 solvent for numerous groups of compounds, whence it follows 

 that A and T being known, the molecular weight of the sub- 

 stance in question may be determined from the equation 

 M = T/A. This method of Raoult's, which is of value in cases 

 where a vapour density determination is not possible, has been 

 employed by the authors to determine the molecular weights of 

 the following carbo-hydrates : dextrose, cane-sugar, maltose, 

 milk-sugar, arabinose, and raffinose, and also that of mannitol 

 (the solvent being water), with results which lead to formula> 



•^ = A, where C is the observed depression produced by 



