Search

Dehydrogenation of 5α-3-ketosteroids with cell-free preparations of Nocardia restrictus involves a cis removal of the 4α and 5α hydrogens while dehydrogenation of 5β-3-ketosteroids proceeds by a stereospecific removal of the 4α and 5β hydrogens.

Metabolic studies of bithionol sulfoxide using labeled compounds were carried out in rats. It was found that bithionol sulfoxide was not only oxidized to bithionol sulfone but also reduced to bithionol (sulfide). The metabolic fate of bithionol sulfone was greatly different from that of bithionol. Bithionol sulfone was excreted mainly in urine as 3, 5-dichloro-2-hydroxyphenylsulfonic acid, whereas bithionol was excreted mainly in bile as a glucuronide conjugate. The presence of 3,5-dichloro-2-hydroxyphenylsulfonic acid and inorganic sulfate was demonstrated in the urine of rats given bithionol sulfoxide. It was assumed that 3,5-dichloro-2-hydroxyphenylsulfonic acid was formed by the cleavage of the C-S bond of bithionol sulfone molecule and that inorganic sulfate was produced by the cleavage of the C-S bond of bithionol sulfoxide molecule. Metabolic study using 3H-bis(2-hydroxy-phenyl)-sulfone suggested that catechol was formed together with sulfonic acid by the cleavage of the C-S bond of bithionol sulfone. It is considered from the above results that the metabolic fate of bithionol sulfoxide consists of 3 different pathways: the first is reduction of bithionol sulfoxide to bithionol (sulfide); the second is oxidation of bithionol sulfoxide to bithionol sulfone; and the third is cleavage of the C-S bond of bithionol sulfoxide.

A new process has been developed, in which the cyclopropenoid groups in cottonseed oil can be selectively and continuously hydrogenated under mild conditions. This process utilizes nickel in a fixed-bed reactor, thereby eliminating the ex-pensive filtration commonly associated with slurry reactors.

1. It was confirmed that the colourless alga, Prototheca zopfii converts glucose completely to lactic acid during fermentation. 2. Lactic acid was the only acidic product of glucose fermentation by Chlorella strain 211/1e, 1.4 moles being formed for each mole glucose fermented. This strain produced negligible carbon dioxide and hydrogen; other fermentation products were not identified. 3. In regard to capacity for fermenting glucose, the Chlorella strains examined fell into 4 groups, namely (a) those producing about 0.75 moles lactic acid/mole glucose (strains 8b, 8p, 11f, 11n), (b) those producing about 1.3 mole lactic acid/mole glucose (strains 1e and 11b), (c) those producing acid but not lactic acid (strain 11g), (d) those unable to ferment glucose (strains 1a, 1d and 9a). This grouping of strains agrees well with groupings based on other biochemical criteria.

1. The C-8 proton of 7-methylguanosine rapidly exchanges with the solvent. The half-life of deuterium exchange is 5.5 min at pH 4.1, 28°, while at pH 7 the exchange is too fast to be measured by NMR spectroscopy. 1,7-Dimethylguanosine and 7-methylinosine behave analogously. The mechanism of this exchange seems to involve acidic dissociation of the C-8 proton. Two mechanistic alternatives, namely, tautomerism and reversible hydrolytic opening of the imidazole ring can be ruled out. This behaviour of 7-methylguanosine is analogous to that of compounds related to thiamine. 2. 7-Methylation of guanine residues in DNA results in a similar rapid isotope exchange at C-8. This was shown by methylating [8-3H]guanine-labeled DNA with dimethylsulfate. The amount of tritium released from the DNA as tritiated water corresponded to the amount of 7-methylguanine. 3. This observation provides a simple and selective method for the determination of the extent of 7-methylation of guanine residues in alkylated nucleic acids.

α-crystallin prepared by isoelectric precipitation yielded well-defined powder diagrams in X-ray diffraction. The reflections could be indexed as coming from a hexagonal primitive unit cell with the dimension of a = b = 8·17 A, c = 7·52 A and γ = 120°. The real unit cell is probably a multiple of this. From the preparation two dialyzable components were obtained. These small molecular weight phosphopeptides (1200 and 2000 daltons respectively) themselves yielded crystalline X-ray diffraction patterns which, however, were different from the patterns obtained with the original preparation. The dialyzed α-crystallin itself was amorphous. Upon recombination of the dialyzed α-crystallin with the dialyzate the original crystalline pattern was again obtained. It is proposed that the phosphopeptide components play a role in the organization of the α-crystallin chains into a well-defined geometrical pattern.

Many investigators have reported changes in intra-ocular pressure when the eye, in vitro or in vivo, was subjected to treatment with acids or alkalis. Fischer1instituted such investigations. He used whole eyes of sheep, oxen and pigs from which the connective tissue and the muscles had been removed. After the eyes had been weighed, they were kept in acid solutions of different strengths. At certain intervals they were removed from their respective solutions, dried with filter paper and weighed again. Increase in weight showed the extent of swelling, which was found to be proportional to the time of immersion and the strength of the acid. The greater the concentration of the acid, the greater was the swelling, and if the eyes were kept long enough in the acid solutions, they invariably came to the bursting point. Fischer observed also that the eyes swelled in pure water, but to a

Investigations on the physico-chemical properties were carried out with addition compounds, Na2HPO4·H2O2 and Na4P2O7·2H2O2.(1) From the results of polarography and paper chromatography, it was found that these addition compounds in aqueous solution were separated into corresponding phosphates and hydrogen peroxide, respectively.(2) Addition compounds in crystalline form were fairly stable below 60°C and there was no detectable decomposition of the hydrogen peroxide.However, the stability in aqueous solution was greatly affected by heating. And the decomposition of hydrogen peroxide was significantly accelerated by heating at high temperature. Especially, hydrogen peroxide of Na4P2O7·2H2O2 was more stable than that of Na2HPO4·H2O2.(3) Addition compounds were found to show the hygroscopicity at relative humidity above 60%, and then the hydrogen peroxide was decomposed in accordance with increasing amount of equilibrium water. The stability of Na2HPO4·H2O2 was less than that of Na4P2O7·2H2O2.

Calcium sulphydrate can be made by heating a granulated mixture of plaster-of-paris (calcium sulphate) with granulated wood charcoal (to take off the oxygen). A high temperature is necessary and it is best obtained by means of gas. A muffler is used, i.e., set in cinders or bone ash and the mixture is heated to redness. By this method neither sulphuric acid or sulphid of iron is used. The dry, rose-colored or whitish product is applied to the skin in a wetted condition, or it may be put on dry and then wetted. Hydrogen sulphid is given off, which causes a rather foul smell. The substance is perfectly harmless to the skin and may be left on any length of time and does not even irritate abraded surfaces. It is not patented and can be made cheaply.

A small Gram-negative coccus, which brings about the reductive fission of the hepatotoxic pyrrolizidine alkaloids, has been isolated from the rumen contents of Australian Merino sheep. The organism was cultured in a partially defined medium, without rumen fluid, but containing yeast extract. Strictly anaerobic conditions and the presence of carbon dioxide were essential for growth. With limiting quantities of yeast extract, growth was greatly stimulated by any of several carbohydrates or moderately stimulated by the alkaloid heliotrine plus hydrogen. The products of the reductive cleavage of heliotrine were heliotric acid and 7()(-hydroxy-l-methylene- 8()(-pyrrolizidine. One mole of hydrogen reduced one mole of heliotrine to produce one mole each of the two products, accounting completely for the substrate consumed. Formate in stoichiometric quantities could replace molecular hydrogen as hydrogen donor in the reaction in which heliotrine acted as hydrogen acceptor. With [UCJformate as hydrogen donor 14CO. was evolved in stoichiometric amounts. The additional growth brought about by the degradation of heliotrine was proportional to the amount of heliotrine degraded, the organism appearing to derive energy from the reaction. Under strictly anaerobic conditions neither growth of the organism nor degradation of heliotrine was dependent on or stimulated by the presence of vitamin B12 in the medium. A method is described for the estimation of heliotrine.

An account of experiments on detonation in gaseous mixtures of acetylene and pentane has already been published. Certain further observations are here recorded as an addendum to the former papers. (a) Influence of Pressure on Velocity of Detonation . It was mentioned on p. 157 of the second paper referred to, that further measurements of the velocities of the detonation waves set up in the explosive mixtures investigated were necessary to determine the precise extent of the increase in velocity occasioned by rise of initial pressure.

The effect of hydrogen on the discharge of negative electricity from hot platinum was examined by the writer in 1903 (‘Phil. Trans.,’ A, 352, vol. 202, 1903); it was found to produce a very large increase in the current carried by the discharge. At pressures below 0·1 millim. of mercury the leak was found to increase with the pressure and to fall when the pressure was reduced. The experiments in the paper just referred to were all done with nearly new platinum wires which had not been heated in the gas for any great length of time, because it was known that long continued heating caused the wire to disintegrate, its surface becoming covered with a network of cracks. The present paper contains an account of a series of experiments in which wires were heated for long periods in hydrogen, so that any gradual changes in the effect of the hydrogen could be observed. It appears that continued heating in hydrogen alters the character of the effects observed, so that the behaviour of an old wire may be very different from that of a new one. In the previous paper I suggested that the effect of hydrogen was due to the presence of hydrogen in the surface layer of the platinum, and this view appeared to be supported by the facts. Professor O. W. Richardson (‘Phil. Trans.,’ A, 413, vol. 207, 1906) puts forward a different theory, viz., that the hydrogen alters the state of the platinum, so that the effect may remain even after the removal of all the hydrogen.

Part II of this series of papers dealt with the compressibilities of hydrogen, helium, and mixtures of the two. The empirical result of that paper was to describe the effects of composition and of temperature upon the pressure- volume relationships in these mixtures. The chief theoretical results were (i) to show that the partial pressure law of Lennard-Jones quantitatively covers the facts; Dalton’s partial pressure law being inapplicable, as we had already proved in other cases in Part If; (ii) to measure the coefficients of the fields of attractive and repulsive force involved in an encounter between a pair of these molecules, by applying Lennard-Jones’ equations; (iii) to deter­mine the kinetic diameters of the molecules of helium and of hydrogen. The kinetic diameter of a molecule depends upon the temperature, being less at a high temperature than at a low. It appeared that at a given temperature, and especially when this is not a low one, a molecule of one of this pair of gases preserves the same diameter whether it is colliding with another of its own kind or with a molecule of the other kind. If this rule were generally applicable, the isotherms of a mixture could be predicted from those of the pure com­ponents. The case of helium and hydrogen was rather a special one, in that both gases deviate positively from Boyle’s law at all ordinary temperatures, and present no great range in the properties measured. Both kinds of molecule are light, small, and "hard," their behaviour in the mass is not necessarily typical, and the theoretical deductions from it might not be generally true. Accordingly, we have extended the work so as to study mixtures of each of those two gases in turn with argon .

In the first part of this paper results of experiments are given on the radiation emitted during the explosion and subsequent cooling of mixtures of various strengths and densities of Cambridge coal-gas and air. Bolometric measurements were made of that part of the radiation from the hot gaseous mixtures which was transmitted through clear plates of fluorite, quartz, plate glass, and water (contained between two plates of glass). The fluorite (6 mm. thick) transmits very approximately 95 per cent, of the total radiation emitted by the gas; the quartz (also 6 mm. thick) transmits about 70 per cent, of the radiation from water vapour and cuts off a very large proportion of that from CO 2 ; the water cell transmits practically only luminous radiation. It has been therefore possible to estimate fairly accurately the total radiation emitted by the gas, and, roughly, the proportions emitted by water vapour and by CO 2 , and also the amount of energy in the luminous radiation. The radiation emitted in the explosion of a 25-per-cent, mixture of hydrogen and air has also been measured. The second part of the paper consists of an investigation into the diathermancy and emissive power of the hot gaseous mixture after explosion. The conclusions drawn from these experiments offer an explanation of many of the peculiar results given in the first part.

In a paper called “The Chemical Constant of Hydrogen Vapour, and the Entropy of Crystalline Hydrogen,” the writer has investigated the vapour pressure of crystalline hydrogen at very low temperatures. He used the Einstein-Bose statistics for the hydrogen gas, and obtained results slightly different from those of Fowler, who had used the classical statistics for the vapour phase. The result found by the writer for the chemical constant i ' was in slightly better agreement with experiment than Fowler’s result, being larger than Fowler’s by log 10 1·04 = 0·02 at the temperatures of Eucken’s experiments. Also, the writer found that when hydrogen gas was condensed to the solid phase at these very low temperatures, the ratio of the number of ortho-hydrogen molecules to the number of para-hydrogen molecules in the crystalline phase, provided that most of the molecules were in the gaseous phase, was not 3 : 1 but instead about 3 ⅙ : 1. However, there was a mistake in the writer’s calculations. He carelessly omitted, from equations (5) and (5') of his paper on hydrogen, the factors involving the work of evaporation χ at the absolute zero, per molecule.

As soon as we found that the glow of radium bromide consisted mainly of light from nitrogen stimulated into luminosity by the radium, and giving the negative pole spectrum, we formed the intention of photographing the spectrum of the glow when the radium bromide was placed in an atmosphere of hydrogen, primarily in the hope of finding an answer to the question raised in our first paper, “Have we to do with occluded or with atmospheric nitrogen?”, and, in the second place, to determine whether the radium is able to render hydrogen luminous. In these experiments some unexpected results came out, which made it desirable to repeat them many times. This circumstance, together with the long exposures necessary—from 10 to 14 days—and the slow changes which we found to take place in the radium when allowed to remain in the hydrogen for long periods, reckoned in months, have necessarily delayed the publication of this paper. The investigation is still in progress, but it seems desirable not to delay any longer the publication of the results which have been already obtained.

Of the three related reactions 2N 2 O = 2N 2 + O 2 ............ [1] 2H 2 + O 2 = 2H 2 O ..............[2] N 2 O + H 2 = N 2 + H 2 O ................[3] only the first two have hitherto been studied. The investigation of the kinetic relation of the third to the first two is the object of this paper. In the preceding paper it has been shown that the thermal decomposition of nitrous oxide into its elements is a homogeneous reaction in which practically every pair of nicrous oxide molecules react which collide under the condition that their joint energy exceeds about 58,000 cals, (for 2 gram molecules). This decomposition is uncatalysed by platinum or by rhodium. The combination of hydrogen and oxygen is, on the other hand, a reaction very dependent on catalytic influences. Bodenstein (‘Z. Physikal. Chem.,’ vol. 29, p. 665 (1899)) found that between 482° C. and about 600° C. the combination proceeds exclusively on the walls of a porcelain containing-vessel. Platinum, rhodium, and other metals have long been known to have a very pronounced catalytic action on a mixture of hydrogen and oxygen. Langmuir (‘Trans. Faraday Soc.,’ vol. 17, p. 621 (1922)) has studied the kinetics of the interaction of hydrogen and oxygen on the surface of a platinum wire, and finds that between 300° and 600° abs. the rate of combination is approximately proportional to the pressure of the oxygen and inversely to that of the hydrogen. There is now abundant evidence that catalytic reactions occur within a layer of adsorbed gas not more than a molecule or so deep, in immediate contact with the surface, and the interpretation of Langmuir’s results is that between 300° and 600° abs. the surface of the platinum is nearly completely covered with a layer of hydrogen and that reaction occurs when oxygen molecules enter gaps in this layer, the number of free spaces being easily shown to be inversely proportional to the pressure of the hydrogen. Turning now from the reactions [1] and [2] to the related reaction [3], the following questions present themselves, namely:— ( a ) whether nitrous oxide and hydrogen undergo a homogeneous bimolecular interaction at temperatures below that at which [1] takes place; ( b ) whether hydrogen and nitrous oxide interact catalytically on the surface of platinum. On the one hand, platinum becomes covered with a film of hydrogen which is activated for reaction [2], while on the other hand, platinum has no activating effect on nitrous oxide for reaction [1].

In a paper recently read before this Society, the author described some experiments on the length of the Crookes dark space under varying conditions in different gases. While the gas hydrogen was under this investigation, a slight inequality of light was noticed very close to the cathode, which, under the prevailing conditions, was not definite enough to warrant further attention at the time. When, however, helium was introduced into the apparatus, this phenomenon became strikingly clear, showing itself to be a hitherto undescribed dark space very close against the cathode and inside the Crookes dark space, possessing very different properties from the latter. By the time the measurements of the Crookes dark space in helium were completed, the behaviour of the new dark space had suggested a simple explanation, which led to a series of experiments, of which this paper is a description. Apparatus . —The preliminary observations of the new dark space were made in the “guard ring cathode” discharge tube already described, but when it was realised that an accurate knowledge of the current density was not required, this was replaced by a smaller cylindrical tube, 8 cm. in diameter, with more uniform walls and plane aluminium cathode and anode. With this exception, the apparatus was entirely as described in the previous paper.

In a previous paper we have described a method of producing high velocity positive ions having energies up to 700,000 electron volts. We first used this method to determine the range of high-speed protons in air and hydrogen and the results obtained will be described in a subsequent paper. In the present communication we describe experiments which show that protons having energies above 150,000 volts are capable of disintegrating a considerable number of elements. Experiments in artificial disintegration have in the past been carried out with streams of α -particles as the bombarding particles; the resulting transmutations have in general been accompanied by the emission of a proton and in some cases γ -radiation. The present experiments show that under the bombardment of protons, α -particles are emitted from many elements; the disintegration process is thus in a sense the reverse process to the α -particle transformation.

In a previous paper* measurements were described of the thermal conductivity of twelve different gases in what may he termed a “free-path vacuum,” that is, at pressures so low that the molecules conducting the heat from the hot to the cold surface do not, as a rule, experience mutual encounters. It was shown ,that at sufficiently low pressure the conductivity of all the gases was proportional to the pressure, and the conductivity K (defined as the calories dissipated per second, per 0·01 mm. pressure of gas per square centimetre of hot surface, per 1° difference of temperature between the latter and its surroundings) was compared with the theoretical conductivity Q, as calculated approximately from the molecular heat and mean molecular velocity of the gas, by means of the kinetic theory, on the assumption that the heat interchange between the molecule and the surface it impinges upon was perfect. For argon and neon the ratio K/Q (1·09 and 1·04 respectively) was in gratifying agreement with this assumption, but for all the other gases the ratio was less than unity. For these the ratio was greater than 0·66, except for helium and hydrogen, for which the very low values 0·5 and 0·25 respectively were found. The suggestion was hazarded that possibly for these light gases the interchange of heat is imperfect, owing to the greater velocities at which the molecules move. In the present paper some of the earlier measurements have been repeated with the original apparatus, with better provision for keeping the tempera­ture of the surrounding water jacket uniform. Then the apparatus was rebuilt to allow of the measurements of the conductivity to be taken over a wide range of temperature, both of the hot and cold surface, and the effect of variation of the temperature on the ratio K/Q was examined. Measure­ments were confined to the three gases—hydrogen, helium, and argon Incidentally the effect on the conductivity of hydrogen of using a hot palladium surface instead of one of platinum was examined. The result of these new experiments has been to negative the suggestion already referred to, that the discrepancies between the found and calculated conductivities might be due to imperfect interchange of energy on impact. The ratio K/Q appears to diminish as the temperature at which the experiments are performed decreases and to increase as the temperature is increased, and no explanation of this can at present be suggested.

It is known that vacuum tubes frequently show a luminosity of the contained gas after discharge is over. In a previous paper I was able to show that this effect, as it occurs in air, is of the nature of a phosphorescent combustion, and is due to the mutual reaction of nitric oxide and ozone, each formed in the discharge. In a second paper it was shown that other phosphorescent combustions can be observed in ozone, notably of sulphur, sulphuretted hydrogen, acetylene, and iodine. Some of these give continuous spectra, but the majority band spectra. In the first paper it was stated that pure nitrogen gives no afterglow whatever, and, with the simple induction coil discharge with which I was then working, this has been frequently verified since. Mr. Percival Lewis has however, described an afterglow obtained in nitrogen when a jar discharge with spark-gap is used. I had no difficulty in obtaining this glow as soon as the jar discharge was used, and have applied to its examination the method used in the former papers. This is due to Sir James Dewar, and consists in drawing a current of gas through the vacuum tube into an observing vessel, where the glow is developed, and thence into an air pump, which must be a mechanical one of good construction, driven by power. It is thus possible to examine the properties of the glowing nitrogen much more satisfactorily than can be done by intermittent examination after successive discharges.

In some previous papers experiments have been described establishing various results when an electric discharge passes through a mixture of hydrogen and oxygen at low pressures. The results, which were very complicated, suggested a theory which satisfactorily explained them and throws a light upon the manner in which chemical effects are brought about by an electric discharge. The experiments to be recorded in the present paper were undertaken with the object of testing the theory further and of providing data for developing it. But before describing the new experiments it will probably be useful to sketch the results of the previous experiments.

During the course of investigation of the bands at λλ 5622, 5211 and 4845, emitted by the magnesium arc in hydrogen at low pressures, Prof. A. Fowler observed that they were always accompanied by a further band at λ 2430 and by series of double lines in the region λ 2940 to λ 3100. These features of this spectrum seemed to merit further study in view of the important part played by the spectra of other molecules with 13 electrons (CN, BO, BeF, CO + , N 2 + ) in the classification of molecular energy levels. Further, MgH is one of the interesting series of hydrides (BeH, MgH, CaH, ZnH, CdH, HgH) which show a pair of excited P states, with doublet separation increasing with molecular weight, closely resembling the lowest 2 P state of the preceding monovalent atoms (Li, Na, K, Cu, Ag, Au). An account of an analysis of the band at λ 2430 was given in a previous paper; the present paper deals with the series of double lines. For convenience the system in the visible region is referred to as the α-system, the one represented by the band at λ 2430 as the β-system, and that about to be described as the γ-system.

Prof. McLennan and others have published in these Proceedings a paper in which they have given results of their measurements of the intensities in the secondary spectrum of hydrogen. The experimental results mentioned in the tables of that paper, however, are only densities, and no attempt was made to find from those densities the real values of intensity in the spectrum. The relations between density and intensity, however, is not so simple as McLennan supposes, as is shown in fig. 1 which follows this. In this paper it will be shown that for theoretical investigations on the secondary spectrum it would be dangerous to use the figures given by McLennan. We shall do this at the moment for a region from 4500-4900 Å.; the real intensities in this region will be shown to differ considerably from those given by McLennan. The intensities of about 230 lines have been measured by the method developed in our Institute. Further, our work shows that the source of error, already mentioned by McLennan— e. g . (p. 281), the difference of sensitivity of photographic plates in this region—can be considerable. Fig. 2 represents the sensitivity as a function of wave-length for the plates used (Ilford Special Rapid). Measurements for other regions of the secondary spectrum will be published soon. The application of the intensity rules is hardly possible at present, as the number of lines of which the classification is certain is too small, and also the wave-lengths are not known with sufficient accuracy. In this paper we give, in addition to the measurements of intensities, the wave-lengths of a number of complex lines not described or uncertain in existing literature.

1. Introduction . —A previous paper has described a method of detecting small changes in the thermal efficiency of encounters between gas molecules and a solid surface. This efficiency determines the rate at which conductive equilibrium is re-established between filament and walls of a Pirani gauge chamber, when the pressure is altered within a range of 10 -1 to 10 -4 mm., the medium of thermal exchange being hydrogen. In the paper it was shown that when two such gauges are balanced in a resistance bridge and simultaneously evacuated through long capillaries, the disturbance of balance, due to unequal rates of gas flow and to the finite time for reaching thermal equilibrium, passes through a maximum at a characteristic time t (max.), t (max.) has a lower limiting value of 120 seconds, dependent on the dimensions of the apparatus, and above that its value varies with the thermal efficiency of the gas-solid collisions; it was shown that a decrease in t (max.) from 10 minutes to 6 minutes, consequent on outgassing, corresponded to a 17 per cent, increase in the accommodation coefficient “ α ,” as the adsorbed layers were removed from the glass. In the present paper the method is extended to determine the change in accommodation coefficient for H 2 when a hydrogen layer of monomolecular thickness has been deposited on the glass. Since no chemical reaction can be invoked under the conditions below specified, these experiments isolate the purely physical part of the changes in α which accompany the formation of such active monomolecular layers as are discussed in the chemistry of heterogeneous reactions.

The principal objects of this investigation have been to examine the part played by the surrounding gas in the production of ions by hot metals and to discover, if possible, the mechanism by which the positive ions originate. In what follows, previous work on ionisation by hot metals will not be described, except in so far as it bears directly on the questions investigated, since the historical part of the subject has been fully treated in previous papers by the writer, and others. The present communication deals chiefly with the emission of positive ions from hot platinum, as earlier work has yielded much more information concerning the negative ionisation. In 1901 the writer showed that a great number of facts in connection with the negative ionisation from hot metals could be explained by supposing that the electrons, of which the ions consist, were produced in the metal itself, from which they escaped by virtue of their kinetic energy. This theory makes the negative ionisation a function only of the metal surface and its temperature, and therefore independent of the nature and pressure of the surrounding gas, except in so far as this may have the effect of modifying the nature of the metallic surface. H. A. Wilson has confirmed this part of the theory by showing that the negative leak, except when ionisation by collision occurs, has the same value in air, nitrogen, and water vapour over a wide range of pressures. Wilson also showed, however, that hydrogen greatly modifies the negative leak. The experiments in the present paper seem to show that the effect of hydrogen is due to some change it produces in the platinum surface; its abnormal behaviour is probably bound up with its electropositive character.

Since publishing the last paper of this series, in which were recorded the results of our experiments upon the behaviour of hydrogen-air and carbon monoxide-air mixtures when exploded in our bomb apparatus at varying initial pressures between 3 and 75 atmospheres, we have been enabled, thanks to further substantial aid from the Society’s Government Grant Committee, to instal in the Fuel Research Laboratories of the Imperial College of Science and Technology, South Kensington, a new chrome-nickel steel bomb (No. 3), of similar design to the one (No. 2) previously employed by us, but capable of withstanding explosion pressures up to 2,000 atmospheres. This has enabled us to extend the research to still higher pressures than would have been safe with the old bomb, and the present paper embodies the results of our further experiments with the mixtures in question at varying initial pressures between 75 and 175 atmospheres. A review of these results, in conjunction with those already published in our previous paper ( q. v .), besides providing further strong evidence in support of our view of the activation of nitrogen in the explosion of carbon-monoxide—oxygen—nitrogen mixtures at high pressures, a subject which we have already fully dealt with, throws further light upon other important aspects of gaseous explosions which have always been keenly discussed by chemists and engineers.

The ‘Proceedings of the Royal Society’ for 1860 contain a paper by Plücker, which gives an account of the first observations of the spectrum of the luminous discharge through mercury vapour at a low pressure. Plücker used a vacuum tube with mercury electrodes, and he observed and made measurements of the wave-lengths of ten lines. A few years later, working with Hittorf, he found that the mercury spectrum may be obtained more brightly when a Leyden jar and spark gap are used in parallel with the tube. Other conditions affecting the lines observed in the vacuum tube spectrum of mercury have since been recorded by various investigators; for instance, the widening of the lines with increased pressure was observed by Ciamician, and the effect of the presence of different gases in the vacuum tube on the brightness of the mercury lines was investigated by Sundell, who found that the mercury lines were visible when the tube contained hydrogen at considerable pressures, but that with oxygen or nitrogen they could only be seen when the pressure was very low. The spectrum of the light from the mercury arc was first investigated by Liveing and Dewar, and afterwards very completely by Kayser and Runge, but the first thorough investigation of the spectrum of mercury in vacuum tubes was that of Eder and Valenta, published in 1894. These observers found that the lines obtained from a vacuum tube at low pressures were much sharper than those given by the arc or spark. The number of lines obtained depended on the current density and on the temperature of the vapour. The spectrum richest in lines was obtained by having one part of the vacuum tube hot and the rest cold, so that the mercury distilled through the capillary. Using a Leyden jar they were then able to measure a great many new lines. From the wider parts of the vacuum tube they obtained a banded spectrum, but this (which was first observed by them) was seen best in the capillary when the discharge was passed without a Leyden jar. Introducing capacity into the circuit had the effect of breaking up these bands into an immense number of fine lines—the “rich line spectrum”—some 670 lines are recorded in their paper.

In a recent paper the writer calculated the vapour pressure of hydrogen crystals, using the Einstein-Bose statistics for the gaseous phase. The work was an extension of that of R. H. Fowler, who had used the slightly less accurate classical statistics for the hydrogen gas. In this paper we propose to apply similar methods of investigation to chlorine. The investigation will have to be different in some respects, however. Hydrogen was considered to consist of a mixture of two gases, para- and ortho-hydrogen, which retained their individuality over long periods of time at low temperatures. Due to the existence of two isotopes of chlorine, we shall here have five gases to consider instead of two. Further, hydrogen molecules almost certainly can rotate quite freely in the crystals of hydrogen; on the other hand, molecules of chlorine almost certainly can not rotate at all in crystals of chlorine.

Since the publication of some recent papers on molecular fields, some new experimental information has become available, which permits of further determinations of the forces between molecules. Hydrogen, nitrogen and neon are now added to the list of gases whose isotherms have been obtained by the precise methods of Holborn and Otto. The publication of these results for neon is of special interest, because one determination of the molecular field of neon has already been made, and it is valuable to have another independent method of attacking the same problem. A method of determining molecular fields from measurements of the isotherms of a gas has been described in an earlier paper. It proceeds on the assumption that the molecular field is spherically symmetrical and that it can be expressed in terms of inverse power laws, one to represent the repulsive force and one to represent the cohesive force. The method shows whether any particular model is a suitable one or not, and when it is, leads to a determination of the force constants.

In a previous communication it has been shown that if a very long vacuum tube of moderate bore, filled with hydrogen at a pressure of ½mm., is operated by a direct or alternating high potential current, the secondary spectrum appears only at the ends of the tube in the vicinity of the electrode bulbs, the central portion showing the lines of the Balmer series, with a faint trace only of the secondary spectrum. By this method photographs of the series down to the twentieth member were obtained. In more recent work the series has been photographed to the eighteenth line in the third order spectrum of a 7-inch plane grating with a lens of 20-feet focus, and the wave-lengths determined to within a few thousandths of an Ångström. This work will be described elsewhere. Practically all of the very peculiar effects described in the paper referred to above have been explained, and in the pursuit of some of the more elusive phenomena, some extremely interesting properties of atomic hydrogen gas have come to light which will be described briefly in the present paper. The work developed out of a study of what I referred to in the earlier paper as “Infected Spots.” It was frequently observed that white spots sometimes appeared along the central portion of the tube, which normally is fiery-purple in colour, and almost invisible through a green colour filter. These spots showed the secondary spectrum of hydrogen, with the full intensity exhibited at the ends of the tube, some fifty times as intense as in adjacent portions of the tube which gave the nearly pure Balmer spectrum.

In the preceding paper, p. 722, Oliphant, Kinsey and Rutherford have given an account of the examination of the disintegration of lithium by protons and by ions of the heavy isotope of hydrogen, using electrical counting methods, and have shown that the results of their experiments lend strong support to the views of the modes of disintegration which they there suggest. Certain of these conclusions may be more completely examined by photographing the tracks of the disintegration particles in an expansion chamber and with that object we have made the experiments described below. In the course of this work a great amount of experimental data has been collected which will require a more detailed analysis; in the present paper the photographs described have been selected with the object of testing the above-mentioned theories. It is possible that the photographs show evidence of other modes of disintegration, but in view of the time required for a full analysis, we publish here only an account of the more obvious phenomena. The apparatus used for the production of the high voltage and its application to the tubes used for accelerating the bombarding particles was that described by Cockcroft and Walton, and potentials up to about 400 kilovolts were used. The first attempts to work an expansion chamber in conjunction with that apparatus showed that the maximum number of disintegrations produced per second was much too small, and considerable time was spent in attempting to obtain a more intense beam of protons. The form of discharge tube finally adopted was that described by Oliphant and Rutherford, This has been found much more definite in behaviour than the glass discharge tube used in the early work of Cockcroft and Walton. The total positive ion current measured at the target is at least ten times greater than could be obtained from the latter tube, and the number of disintegrations produced per second has been increased by an even larger factor. It is probable that the new type of tube gives a larger ratio of protons to molecular ions in the beam—this ratio being more liable to fluctuation with the glass discharge tubes. With the present arrangement, using the maximum output of current and voltage, it is possible to obtain over 100 tracks per expansion from a lithium target a few square millimetres in area.

1. This paper deals with the continuation of our endeavour to arrange the lines of this spectrum in series by starting from a study of the lines which are selectively changed in intensity in electron discharges in hydrogen at a low pressure as compared with discharges in a Geissler tube of the type which is most usual in spectroscopic observations. The previous work has been described in two papers which we shall assume to be available in dealing with what follows. 2. A Second P, Q, R Combination .—We commence by considering the following lines which can be arranged as P, Q, and R series with the enumeration shown.

The measurement of the intensity of an X-ray beam in absolute units is in theory most satisfactorily accomplished by a determination of its heating effect. The method, however, is attended by considerable experimental difficulties, so that its application is very limited, and in practice it is usual to replace it by a determination of the ionization produced when the beam is passed through a gas. To correlate the ionization with an absolute intensity requires a quantitative knowledge of the details of the interaction between the X-rays and the molecules concerned and of the ionization of the gas by the ejected electrons. It sometimes happens that the processes involved about which we know least are relatively unimportant, so that a fairly reliable correlation can be made; and much work has been done on the application of the ionization method to X-ray dosimetry. But in general a quantitative correlation between ionization and intensity is not possible. A further study of the ionization of gases by X-rays is therefore desirable; moreover it may be made to yield important information concerning the processes involved. The early development of the physics of X-rays contains many examples of this, and more recently an important contribution has been made by Stockmeyer. The events leading to the ionization of a heavy gas are exceedingly complicated, whereas in the light gases (hydrogen and helium) some of these events are absent or else occur to a negligible extent, so that the interpretation of experiments with the latter becomes simpler and more reliable. These gases are therefore specially worthy of study. Moreover, for them the application of quantum mechanics leads to the most definite results for comparison with experiment, and in particular permits of a direct test of some aspects of Dirac’s theory of recoil scattering. The ionization due to the gas itself is, however, very small, and may even be less than the secondary ionization due to electrons liberated from the chamber walls. The technique used in ionization measurements with heavy gases is therefore unsuitable. Hitherto the only attempt made to extend such measurements to light gases is an experiment carried out in 1915 on hydrogen by Shearer who, however, obtained very variable results and an ionization markedly smaller than that to be expected from recoil electrons alone. Moreover his experimental method is now open to criticism in view of our greater knowledge of X-rays, and in particular the fluorescent radiation used was of doubtful homogeneity. The present paper will describe a new technique suitable for quantitative measurements of the ionization produced by X-rays in light gases, and in another paper it will be applied to a re-investigation of hydrogen.