Abstracts of Papers Communicated to the Royal Society of LondonSource: Proceedings of the Royal Society of London. Series A, Mathematical and PhysicalSciences, Vol. 177, No. 971 (Mar. 18, 1941), pp. S5-S8Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/97472 .

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ABSTRACTS

OF PAPERS COMMUNICATED TO THE ROYAL SOCIETY OF LONDON In accordance with a resolution of Council, summaries or abstracts of papers are to be published as soon as practicable. The publica- tion of such abstracts in no way indicates that the papers have been accepted for publication in any fuller form. These abstracts are issued for convenience with the " Proceedings of the Royal Society of London" but do not form a part of the "Proceedings".

1 FEBRUARY 1940

The measurement of tides by means of the Fave pressure gauge. By R. H. CORKAN, A. T. DOODSON, F.R.S., and J. PROUDMAN, F.R.S. (Received 13 December 1939.)

The measurements and analyses described in this paper were made with the object of calculating the variable parts of the components of the horizontal gradients of pressure in the sea. For such a purpose, and in the part of the Irish<Sea considered, the principal harmonic constituent of the tidal elevation must have its amplitude determined to the nearest cm. and its phase determined to the nearest 03?.

The instruments used were three models of the maregraphe plongeur Fave. Though this instrument has been described in great detail by its designer, very little has been previously published on results obtained with it. Our greatest difficulties were in connexion with the calibration of the instruments.

The results obtained from the records taken at sea may be regarded as giving a good determination of the principal harmonic constituent of the tides at the stations considered, but not sufficiently good for a reliable calculation of the horizontal pressure gradients.

The investigation has given us very valuable experience, and when opportunity next occurs we intend to make further measurements.

The dynamic constants of human muscle. By A. V. HILL, SEC.R.S. (Received 14 December 1939.)

The characteristic equation of muscle is modified to meet the case of a constant mass accelerated instead of a constant force overcome at uniform speed.

The theory is compared with experimental results obtained on human arm muscles with an inertia wheel. The agreement is good.

Abstracts [ s 5 ] 2

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8 6 Abstracts of Papers

The value of the dynamic constant b is deduced. Its order of size is muscle length per second. PO/a cannot be very far from 4, its mean value in frogs' muscle.

The maximum speed of shortening (unloaded) is determined experimentally. This is of the order of size Pob/l de(luced from theory.

The mechanical efficiency, the optimum speed, the possibility of reflex inhibition during rapid shortening, certain practical applications and some proposals for fiurther research are discussed.

The photolysis of ammonia. By E. A. B. BIRSE and H. W. MELVILLE. (Communicated by J. Kendall, F.R.S.-Receivedl 15 December 1939.)

The anomalously low stationary hydrogen atom concentration (luring the photo- decomposition of ammonia is (lue either to the fact that the primary photochemical efficiency is not unity or that the hydrogen atoms are removed at an abnormally fast rate. It is shown by utilizing the para-hydrogen conversion that photodecom- posing ammonia has no effect on the stationary hydrogen atom concentration of the conversion and therefore the low conceintration of the ammonia photolysis must be due to inefficiency of the primary process. The primary efficiency is determined by a careful comparison of the mercury sensitized and the ammonia sensitized conversion of para-hydrogen. A method is developed for measuring accurately the rate of pro- duction of hydrogen atoms, which method is essential to the foregoing determination. This primary efficiency is found to be 0 58.

A method is also developed for measuring the lifetime of amine radicals. Similar experiments with trideuteroammonia are also described. The primary

efficiency is 0-28. A revised and simplified scheme for the ammonia photolysis is given as a result of

these new experiments.

The reaction of atomic hydrogen with hydrazine. By E. A. B. BIRSE and H. W. MELVILLE. (Communicated by J. Kendall, F.R.S.-Received 15 December 1939.)

Trhe efficiency of the r eaction of atomic hydrogen with hydrazine has been measured in the temperature range 20-200? C by comparison with that of the hydrogen atom sensitized conversion of para-hydrogen. A static system is employed, the hydrogen atoms being produced by excited mercury atoms. The energy of activation is nearly the same as that of the para-hydrogen conversion, namely ca. 7 kcal. and the steric factor is ca. 10-2. From these results it is shown that hydrazine is not responsible for the low stationary hydrogen atom concentration in the photolysis of ammonia as has hitherto been supposed.

Although the hydrogen atoms react with hydrazine very efficiently the quantum efficiency of this reaction is only 0-4 instead of the expected value of 2. An explanation of this result is suggested.

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Abstracts of Papers S 7

It is also shown that photodecomposing hydrazine converts para-hydrogen. This is taken to mean that the primary decomposition is represented by

N2H,+hv = N2H3+ H.

The quantum efficiency of the mercury sensitized decomposition of hydrazine has been found to be 0 37. An explanation of this unexpectedly low value is given.

A new simplified method of analysing the ternary mixture p-H2--n-H2-N2 is described.

The phosphorescence of various solids. By J. T. RANDALL and M. H. F. WILKINS. (Communicated by M. L. E. Oliphant, F.R.S.-Received 18 December 1939.)

A complete understanding of luminescence phenomena in solids involves the study of such properties as emission and absorption spectra, decay laws of phosphorescence, and photoconductivity. In this paper accurate results on the decay laws of phos- phorescence of a number of solids are given together with corresponding observations on photoconductivity. Measurements of the phosphorescence of pure and impure solids have been carried out by two methods. In the first and more accurate method the intensity of phosphorescence of an annulus of powder on a rotating disk was measured by means of a vacuum photocell and d.c. amplifier of the electrometer triode type. In the second method an intermittent beam of ultra-violet radiation falls on a stationary specimen; during the illumination period the intensitv of luminescence rises to an equilibrium value, afterwards decaying when the ultra-violet radiation is cut off. By allowing the varying luminescence radiation to fall on the primary cathode of an electron multiplier coupled with an oscillograph, rise and decay curves of various solids can be obtained on the oscillograph screen and photographed for measurement.

In general the results are not simple for compounds activated with impurity. Pure uranyl salts, however, give a simple exponential decay I= I0e-at; moreover, the salts are not photoconductors. The results confirm the idea that the luminescence of these salts is a property of excitation states within the co-ordination group of the uranyl ion. The time of decay suggests that forbidden transitions are involved. Tungstates on the other hand are slightly photoconducting in the pure state, and have a very fast decay.

A number of inorganic solids containing manganese impurity have also been examined; these include cadmium chlorophosphate, zinc mesodisilicate, cadmium silicate, cadmium borate, zinc beryllium silicates and zinc orthosilicate. In all these solids the initial decay is approximately exponential with a slight curvature of the semi-log plot convex with respect to the time axis. In the zinc beryllium silicates and in zinc orthosilicate this curvature is more pronounced, and in the latter case develops into a long phosphorescent tail. In all cases, however, the slope is a function of time and not of phosphorescence intensity, thus showing that the decays are not of the bimolecular type. The photoconduction results show that the pure non- fluorescent compounds and the impure fluorescent ones conduct in general to the same extent. We are inclined to the view that the photoconduction arises from secondary causes such as lattice defects or interstitial matrix atoms. In the solids

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S 8 Abstracts of Papers

cadmium chlorophosphate, zinc mesodisilicate, cadmium silicate, and cadmium borate, we suggest that the decay law is of the type I = Iloe-0t; such a result can easily arise from the non-equivalent positions of impurity atoms in various parts of the crystal. From the slope of the semi-log plot the lifetime of the excited man- ganese ion may be calculated.

The long tail observed for most zinc orthosilicates can best be explained by sup- posing that the absorption process first sets free the excited electrons. This is followed by electron trapping probably in the neighbourhood of the manganese ions. The free electrons recombine with manganese ions very rapidly; these electrons, however, remain in the excited state an appreciable time, thus giving rise to the initial ex- ponential decay. The phosphorescent tail depends only on the rate at which electrons are released thermally from trapped positions.

Comparison of the acceleration due to gravity at the National Physical Laboratory, Teddington, and the Bureau of Standards, Washington. By B. C. BROWNE and E. C. BULLARD. (Communicated by Sir Gerald Lenox- Conyngham, F.R.S.-Received 20 December 1939.)

The values of the acceleration due to gravity at the points used for the recent absolute determinations at the National Physical Laboratory, Teddington, and at the National Bureau of Standards, Washington, D.C., have been compared. The difference found is 1 0969 cm./sec.2. The difference between the two absolute deter- minations is 1-1015 cm./sec.2, whilst that deduced from previous indirect relative connexions is 1-0953 cm./sec.2. The agreement is within the uncertainties of the measurements, and leaves little doubt that the hitherto accepted value at Potsdam is some seventeen parts in a million too great.

The kinetics of decarboxylation in solution. By P. JOHNSON and E. A. MOELWYN-HUGHES. (Communicated by R. G. W. Norrish, F.R.S.- Received 21 December 1939.)

The kinetics of the decarboxylationi of trichloracetic tribromacetic, and trinitro- benzoic acids have been studied over extended temperature ranges in aqueous solution. The results conflict with the formula of Arrhenius, and conform better to an equation of the type

J E Ink c+-1 lnT-RT.

The experimental values of J are fouind to be negative. Decarboxylation reactions thus come into line with catalysed and uncatalysed hydrolyses in aqueous solution.

Certain theoretical considerations are advanced to account for the observations.

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