190 



NA TURE 



[June 20, 1907 



ings fund has now rpached a sum that will sullice for the 

 erection of the arts and administrative portions, and this 

 will enable the present college buildings (formerly the 

 Penrhvn Arms Hotel) to be handed over entirely to the 

 requirements of science. Thus, for a time, the college 

 will be conducted on the lines of certain foreign universi- 

 ties, where the faculties of arts, science, law, and medicine 

 are housed in separate buildings. It is hoped, however, 

 that the completion of the new college by the erection 

 of buildings for the faculty of science will not be long 

 delayed. ".\ considerable moral obligation rests on the 

 Government to assist in this matter, more especially in 

 view of the fact that the death duties arising out of the 

 estate of the late Lord Penrhvn, while representing a 

 heavy financial loss to the people of North Wales, would 

 far riiore than suffice to build and equip the new college. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, May 23. — " Chemical Reaction between 

 .Salts in the Solid .State." By E. P. Perman. Com- 

 municated by Principal E. H. Grifiiths, K.R.S. 



Experiments have been made on the following pairs of 

 salts : — lead chloride and potassium iodide, mercuric 

 chloride and potassium iodide, sodium, carbonate and 

 barium sulphate, sodium sulphate and barium carbonate. 

 The chief points investigated were the effect on certain 

 of these salts of (i) traces of moisture; (2) great pressure; 

 (3) heat. 



It was found that reaction always took place unless the 

 salts were very carefully dried, and that the reaction was 

 accelerated by shaking the mixture, and by the applica- 

 tion of heat or great pressure ; further, that the velocity 

 of the re.Tction is much influenced by the solubility and 

 volatility of the salts. 



The effect of small quantities of some other solvents was 

 also tried. It was found that methyl alcohol caused a 

 reaction between lead chloride and potassium iodide in the 

 same way as water, whilst benzene, chloroform, and 

 ammonia were without result. 



Finally, it would appear that reaction between solid 

 salts is of essentially the same nature as that between salts 

 in solution, and it is suggested that the water (or other 

 solvent) present forms a film on the surface of the salts, 

 and that in this film minute quantities of the salts dis- 

 solve, and there react. In the absence of an ionising 

 solvent there is no chemical reaction, even when the sub- 

 stances are heated or subjected to great pressure. 



Physical Society, May 24.— Prof. J. Perry, F.R.S., 

 president, in the chair. — The measurement of mutual in- 

 ductance by the aid of a vibration galvanometer ; A. 

 Campbell. Carey Foster's method of comparing a mutual 

 inductance with a capacity is one of the most con- 

 venient. The advantage gained by the use of a vibration 

 galvanometer in methods for measuring capacity or in- 

 cluctance led the author to apply it to the Carey Foster 

 and the Hughes-Rayleigh methods. He found it was 

 necessary with alternating currents to modify the Carey 

 I-'oster method by adding a series resistance in the con- 

 denser branch ; this gave an additional formula involving 

 the ratio of a mutual and a self-inductance. This modifi- 

 cation has been suggested by Rowland. The modified 

 method is convenient, the two adjustments required for a 

 balance being independent, and the result not involving a 

 knowledge of the frequency; the use of the vibration 

 galvanometer is an improvement, making the method in- 

 dependent of the wave-form of the current used. The 

 .uithor discussed vibration galvanometers. They belong to 

 the class of tuned instruments. If the detecting instru- 

 ment used in a null method (with alternating current) is 

 adjusted .so that its natural period is in tune with that 

 of the applied voltage, it will be .set into strong resonance 

 and will be enormously increased in sensitivity for this 

 particular frequency, practically ignoring in comparison 

 all the other components of the wave-form. Thus in any 

 method in which the tuned instrument is used, a sine 

 wave-form may be assumed. The author exhibited a 

 vibration galvanometer of another type, having a moving 



NO. 1964, VOL. 76] 



coil controlled bv an adjustable bifilar suspension. By 

 adjusting the tension of this the tuning is easily effected. 

 For measuring the frequency to which a tuned instrument 

 is responding, it is convenient to use the Hughes-Rayleigh 

 method. The author showed such an arrangement in 

 which the slide-wire was graduated directly in frequency. 

 The author gave results of tests of a standard mutual in- 

 ductance of 005 henry. The Kirchhoft method with direct 

 deflection on a ballistic galvanometer, of measured time 

 of swing, gave a mean of 005014 henry, while the Carey 

 Foster method gave 005000 henry ; the probable error of 

 the latter was much smaller than that of the older method. 

 — Note on the rate of decay of the active deposit from 

 radium: W. Wilson and W. Makower. In some experi- 

 ments in which Ihe ionisation produced by the a rays from 

 radium C was balanced against that produced by the more 

 penetrating and 7 rays, it was found that after a short 

 time these two ionisations were no longer e.xactly equal, 

 however carefully they had been adjusted to equality at 

 first. jV similar eftect had been noticed by Brousson, and 

 was attributed to the slowly moving $ rays emitted by 

 radium B which is present with the radium C. Since these 

 ravs arc emitted by radium B, whereas the a and more 

 penetrating 3 ravs arc emitted by radium C, it is to be 

 expected that the rale of decay as measured by these two 

 types of radiation will be different. The authors' experi- 

 ments confirm the view that the observed difference in the 

 rate of decay as measured in the two vessels is due to the 

 slowly moving rays emitted by radium B. — .Apparatus 

 for relay working of long submarine telegraph cables : 

 S. G. Brown. This relay system consists of three parts : — 

 (1) the actual relaying device or drum relay; (2) an in- 

 ductive shunt with closed iron circuit for use across the 

 receiving coil to curb the signals and straighten out the 

 zero ; and (3) a method of applying a local current possess- 

 ing suitable time-lag to the receiving coil to correct the 

 tendency of signals made up of two or more impulses of 

 the same polarity to fall away to zero due to the charging 

 up of the receiving condenser itself. 



Faraday Society. Mav a" — P'of. A. K. Huntirgton 

 in the chair. — Contributions to the chemistry of gold : 

 F. H. Campbell, .\urous iodide, Aul, was prepared and 

 found to decompose at 25°, according to the equation 



2AuIz:l2Au + l2. 

 Since this equation contains only one variable, namely, the 

 iodine, there must be a particular pressure of iodine at 

 which Aul, Au, and I, are in equilibrium. This was 

 found to be 0-943 of that of pure iodine ; any solution of 

 iodine will therefore act on gold if more than 0'943 

 saturated, but not if below this strength. When gold is 

 acted on by a solution of KI and iodine, part is converted 

 into insoluble .Aul and part dissolves. The experimental 

 results with various solutions agree with the equilibrium 

 equations only when the gold is assumed to enter the 

 complex ion in the monovalent condition, i.e. to yield 

 Aul,. ions. The action 3.\uCl = AuClj-|-2.Vu was found to 

 occur at ordinary temperatures and in absence of moisture. 

 — Reduction of some oxides and sulphides by means of 

 metallic calcium : Dr. F. Molhvo Perkin. The author first 

 referred to the well-known powerful reducing action of 

 aluminium, as, for example, its use in the preparation of 

 chromium, ferrosiliton, and other metals and alloys, and 

 its use in the form of " thermite " for welding purposes. 

 He finds that metallic calcium is a still more powerful 

 reducing agent than aluminium. For example, when 

 molecular proportions of aluminium and ferric oxide are 

 mixed together and ignited by means of a fuse of 

 aluminium and barium peroxide, intense reaction ensues, 

 and continues until all the oxygen has been removed from 

 the ferric oxide, and aluminium oxide and metallic iron 

 produced in its stead. When metallic calcium in the form 

 of fine turnings is mixed with ferric oxide and ignited in 

 a similar manner, the reaction is so intense that the 

 mixture is in large part ejected from the crucible. The 

 reaction can be brought under control by mixing 30 per 

 cent, to 40 per cent, of calcium fluoride or 10 per cent, to 

 20 per cent, of calcium oxide with the contents of the 

 crucible. Boron can be obtained by igniting a mixture of 

 boron trioxide with the calculated quantity of calcium and 

 5 per cent, to 10 per cent, of calcium oxide. Attention was 



