In no part of the periodic system it is so difficult to predict anything about missing elements as in the seventh groups in the case of 43 and 75. Mendelejev had good reasons to say nothing about their properties. The seventh group contains a break in the system. Just as it is impossible to derive the properties of the halogens from the homologues of sulphur on one side and those of the inert gases on the other, it is as difficult to predict the properties of the manganese homologues from those of molybdenum tungsten and rutheniumosmium respectivelly.

The Noddacks interpolations between 791 m. p. of Mo0, and 22.5 m. p. of RuO1, between 1800 m. p. of WO, and 55 m. p. of OSO1, are without meaning.

What significance can be ascribed to the melting points for EO, 350 and D2O,, 600 so calculated, when it is remembered that MnO, is an explosive gas at ordinary temperature, and also that manganates are so unstable that they do not occur in nature? Of much greater importance would be the chemistry of the lower oxides which compounds should yield coloured cations of which the Noddacks know nothing. Not much better founded are their data on the occurrence of the manganese homologues in the earth's crust.

Further, the Noddacks papers contain still other data which seems to be unfounded. Thus, they give exact percentage compositions of very complicated mixtures obtained as precipitates, the analysis of which, even if possible, could need an extradordinary analytical skill.

They state, e.g., that they obtained .05, .2, .8 or 5% Rhenium in precipitates although there is neither X-ray spectroscopic nor any other way of estimating this element.

OBSERVATIONS ON THE WORK OF O. BERG.

The chief argument of O. Berg against the negative results of Prandtl's examinations of their specimen said to contain .8% -1% Rhenium was that Prandtl was unable to distinguish any Rhenium lines because he did not even find the lines of Nb and U which were said to be present in about 10 times that quantity. First of all too little was available for complete analysis and secondly Berg's own spectrogram of this specimen did not show any uranium line, nor was there the 75 L, line distinguishable.

The great number of spectrograms which Berg considers necessary to give some positive results support Prandtl's state

ON THE DETECTION OF THE
MANGANESE HOMOLOGUES.

By N. SELJAKOW AND M. KORUNSKI. W. and I. Noddack have criticised Seljakow and Korunski's investigations as they failed to find any indications for manganese homologues in specimens obtained from platinum ores. They explain their negative results by a too small X-ray dispersion (0.06 mm. between CuKa and Ka) as used by the Russian investigators.

Seljakow and Korunski now show that the number 0.06 mm. refers to the width of the slit and that nowhere in their own communication was the dispersion described; they deduce that their dispersion is even greater than that used by the German investigators. The spectrogram showing the dispersion of Zn Ka and Ka, is given. (Abstracted from Physikalische Zeitschrift, 1927, xxvIII, 478.)

GENERAL NOTES.

AMERICAN CRITICISM OF BRITISH

COAL INDUSTRY.

SOME FALLACIOUS OBSERVATION'S Mr. Philip Gee, Director of the Colliery Owners' Publicity Department, issues the following statement :

According to cabled reports an American organisation described as the Institute of Economics has been busying itself for several months in investigating the British Coal Industry.

What may be the competence of the investigators it is impossible to say until their names and qualifications are known, nor is it at present apparent what form their investigations took; but it would, perhaps, have been more seemly for them to have confirmed their immediate efforts to setting in order their own coal industry, in which a strike has been raging for several months. The report appears to make the usual observations about reorganisation" so dear to the mind of the "economist " who does not have to organise a business enterprise from day to day.

66

There is, however, one passage in the cabled reports that should be challenged at once. It is stated-as evidence of the

"inefficiency" of British mining practice --that only one-fifth of British coal is cut by machinery as contrasted with two-thirds in the United States. As a matter of fact, according to the annual report of the Secretary of Mines, 53 per cent. of that coal raised in Scotland is machine-cut and 33 per cent. of that in Northumberland, with varying percentages in other districts.

But possibly the investigation of those American economists did not extend to Sir Richard Redmayne's evidence before the Sankey Commission. Dealing with this very point Sir Richard said :

"It is quite rash and quite wrong to suppose that mechanical coal-cutters can be employed broadcast in all coalfields. They are quite impossible of application in a great number of the Welsh coal mines, and not only in the Welsh coal mines but in a number of other coal mines the United Kingdom because the coal will not stand to be cut. No sooner does the machine proceed to work on the face than the coal falls upon it. You might say you can stay up the coal, but then the machine cannot travel. Again the condition of the roof does not allow of the application.

And in his evidence before the Samuel Commission the same authority said that :-

"Too much must not be made of this comparision (between the quantities of coal machine cut in Britain and the U.S.) for the natural physical conditions in the United States are, on the average, vastly more favourable to machine-mining than in the case of Great Britain."

That is, unfortunately, only too true. Providence has given us most of our coal in narrow seams, whereas the coal in the mines of the United States-true to the American tradition-appears to be located in cliffs. And then, to their natural advantages, they add a working day longer than in Europe. According to the report of the Samuel Commission our nominal eight-hour day gives 6 hours working time at the coal face, but" in the important coal States, such as Pennsylvannia, Virginia and Illinois, there is no legal limitation of hours. The standard working time is usually given as 8 hours a day for 6 days in the week. This appears usually to mean 8 hours in the actual work-place, i.e., exclusive of time spent in getting to and from the pit mouth. This would make the working time materially longer than in most European

countries."

Finally, the Investigators of the Institute of Economics are reported as observing that here is no room for the "several thousand"

"There appears little doubt that in the United States of America there are opened out a greater number of coal mines than are actually required. It has been stated on good authority in America that if all the coal mines of the United Staes were worked all the year round instead of, on an average, of nine months in the years, there would be provided in that country a surplus of about 200,000,000 tons of coal per annum. From which it is evident that the United States must strive more and more to obtain a larger share of the export trade in coal and that Great Britain can only maintain her present leading position by producing cheap coal and carying it by land and by sea at cheap rates."

And that last sentence may account for the apparent desire of certain persons in the U.S. to decry a very dangerous competitor.

DEATH OF PROFESSOR SVANTE
ARRHENIUS.

The death took place on Sunday, October 2, at the age of 68, of Professor Arrhenius, the great Swedish scientist. His fame was international. He came to London in 1914 to receive the Faraday Medal of the Chemical Society, on which occasion Sir William Crookes (founder of the Chemical News) said:" The world is deeply in need of researchers both of the type of those whose genius is characterised by that fertility of resource in experimental investigation exhibited by Faraday and of the type of Arrhenius. Both are revolutionaries and founders of new kingdoms. The world's debt to them is incalculable."

NEW IRISH FREE STATE PATENTS AND TRADE MARKS ACT. IMPORTANT LEGISLATION.

Messrs. Rayner & Co., the well-known Chancery Lane Patent Agents, call attention to the new situation which is created by the coming into force of the new Patents and Trade Marks Act in the Irish Free State on October 1, 1927.

Previously, British Patents and Trade Marks have covered the whole of Ireland, but, with the new Act in force they will automatically cease to function in the Irish Free State.

It is therefore necessary, for all holders of British Patents and Trade Marks desiring to retain their protection in Southern Ireland to "validate " their patents and trade marks there.

British patents and trade marks will therefore be continued upon the Irish Register if a certificate of the patent or trade mark is lodged in the Free State and renewal fees paid as in England together with other conditions which are required.

Should any of our readers desire more detailed information on this important subject, Messrs. Rayner & Co., 5, Chancery Lane, W.C.2., will be glad to supply it free of charge.

CHAINS AND THEIR USE.

An invaluable booklet has been issued by the Factory Department of the Home Office on "Annealing and Use of Wrought Iron Chains." The information is based on the results of experiments conducted at the National Physical Laboratory. Chain accidents are largely ascribed to brittleness due to skin-hardness and to defects in manufacture, failure to examine chains, and ignorance as to what is a "safe load." This booklet contains essential facts that should be known by all chain users and should be in the hands of both employers and workmen. Its price is only one penny, and employers throughout the country would be well advised to purchase and distribute copies to those whom they employ. It will enable the workman concerned to take an intelligent interest in his work, and if the advice is followed will undoubtedly lead to a diminution of accidents.

BRITISH STANDARD TUNGSTEN

FILAMENT ELECTRIC LAMPS. The British standard specification for tungsten filament electric lamps, No. 161, which was issued in 1924, has been revised chiefly by the addition of four schedules for traction, vacuum train lighting, gasfilled train lighting and gasfilled 'bus lamps. The modifications made are not numerous, the chief one in the general clauses of the specification being the addition of a switching on and off test. The figures in Table II of the schedules for vacuum and in Tables II and III for gasfilled lamps have been slightly modified. The dimensions of the bayonet cap, given in Appendix II, have also been modified to bring them into line with the dimensions recently adopted by the International Electrotechnical Commission.

Copies of this specification, No. 161-1925, can be obtained from the British Engineering Standards Association (Publications Department), 28, Victoria Street, London, S.W.1.

INTERNATIONAL ECONOMIC
CONFERENCE CATALOGUE.

A catalogue of all documents published for the International Economic Conference has been published by the League of Nations. All who are interested should ask for this catalogue, which will be sent free of charge on application to Messrs. Constable and Co., Ltd. (who are the authorised agents for the publications of the League of Nations in this country), 10-12, Orange Street, London, W.C.2.

Notices and Proceedings of Societies

THE FARADAY SOCIETY.

The Effect of Temperature on Diffusion Potentials. By E. B. R. PRIDEAUX.

During the course of work which has been designed to examine the relations between diffusion and membrane potentials, there has been occasion from time to time to test the variation of these with temperature over the ordinary range, in the case of alkali salts of some organic acids. No variation has been found which was above the limit of an error which was to be expected in these experiments. This constancy has some practical importance as enabling measurements to be carried out without a thermostat. A review of the ionic mobilities and transport numbers of strong electrolytes has partly confirmed the present thesis; that the temperature coefficients should be low or perhaps quite negligible over a temperature range of about 10°. Since however the existing data are insufficient, it was decided to investigate the problem in the case of a few typical electrolytes at the two standard temperatures, 18° and 25°, using the ideally sharp flowing junction, which removes the uncertainty as to whether a pure or mixed boundary is present.

temperature may be determined from the transport numbers or ionic mobilities, and in the first place from those at infinite dilution, if as is the case with most uni- univalent electrolytes the transport numbers do not vary within the limits of concentration taken, i.e., 0.1 N and 0.01 N in the present series.

Since the ionic mobilities become more nearly equal as the temperature rises, na or

decreases, and tend to compensate for the increase in the factor RT/nF. If this compensation is exact, the temperature coefficient of diffusion potentials will be zero.

EXPERIMENTAL.

In an apparatus somewhat similar to that described by Scatchard, a flowing junction is set up, which is supplied by two reservoirs containing the two solutions, of concentrations c1 and c2, having equal hydrostatic pressures at the junction. A few drops of a suitable indicator may be added to c, in order to make the boundary visible. The solutions are connected by side tubes with saturated KCl calomel electrodes. The potential differences between these, i.e., the diffusion potentials were measured on a Cambridge portable potentiometer, type B, used with an external galvanometer and scale. The standard of potential was cadmium cell, checked from time to time against an N.P.L. standard. The flowing junction and reservoirs were immersed in a small thermostat regulated by hand. The potential becomes constant at once if the ujnction has been properly set up, and remains so as long as the solutions are supplied. Individual readings agreed as closely as the scale permitted, i.e., to about 0.2 millivolt.

a

Solutions were made from water which had been freed from carbonic acid by a current of air free from carbon dioxide. The sodium hydroxide was freshly made from a carbonate-free stock which was kept in a silver bottle. The potassium benzoate was made from the pure acid, neutralised hot in a silica basin with standard potassium hydroxide, and finally adjusted in the presence of phenylphthalein. Potassium phenyl acetate was prepared in a similar manner. Piperidinium hydrochloride was made from a weighed quantity of the pure base, neutralised by standard acid (to methyl red), diluted to the required concentration and checked by titration with silver nitrate. The acetic acid was made from A.R. agent, and standardised as usual.

re

DISCUSSION OF RESULTS.

A few cases require special comment. The diffusion potential of silver nitrate at 25° is due to Cumming. It was measured by him at a static junction, as the difference between the potentials of two Ag, AgNO,, N/10 and N/100, concentration cells (a) without and (b) with, elimination of diffusion potential by a saturated solution of ammonium nitrate. The present value, at 18°, was also determine dat a static junction, but was a direct measurement of the diffusion potential of the AgNO, concentration chain, the end electrodes being two saturated KCl calomel half-cells which were separated from the silver nitrate by saturated ammonium nitrate. Acetic acid was added as an example of a weak electrolyte, and it was of interest to ascertain whether the Planck theory applies also to this class. It is a favourable case, since the dissociation constant does not change appreciably either with the concentration, or with the temperature within the limits over which these factors were varied. The potentials were found to be as steady as usual, but do not agree as well as usual with the values deduced from the transport numbers and the ionic mobilities, the latter being calculated from the dissociation constant 1.85 × 10-5. Since the experimental values are lower, this may be due to a special difficulty in producing an ideally sharp junction between different concentrations of a weak electrolyte, only a small proportion of which exists as ions.

The diffusion potentials of the other electrolytes, which had been previously recorded, and obtained at static junctions are in good agreement with the present values, showing that the static junction in these cases may give a sufficiently sharp boundary. Together with the other examples, the diffusion potentials of which had not been previously determined in any manner, the Table includes all the principal types of strong electrolytes--acid, alkali, salts of strong acid and alkali, alkali and weak acid, weak base and strong acid, and a weak acid. The diffusion potentials of all these are are found to have temperature co-efficients which are either zero, or not more than 0.5 of a millivolt (except acetic acid) for 7° within the ordinary temperature range. In the first part of this paper it has been shown that this is a consequence of the relation between temperatures and ionic mobilities.

These results may be embodied in the statement that the diffusion potentials between concentrations of the same strong electrolytes have as class very low temperature coefficients.