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The atomic process in ferromagnetic induction
May, I922.]
METHOD OF CALCULATING FLUIDITY.
655
latter can be calculated over a range corresponding to the range of the known values for the first substance ( B ) . • To do this, the values of the ratio T A / T B = R are plotted against the absolute temperatures T~ and a straight line drawn through the points. By multiplying a particular temperature, T~ , by the corresponding temperature ratio (read off from the curve), the absolute temperature, TA, is obtained at which the value of the physical constant of the substance d is equal to that of the substance B at the absolute temperature T~. I f the line does not run through the points (i.e., if c is not constant), it is probable that the experimental data are not accurate, or that one of the substances behaves abnormally. S WARTHMORE, PA.,
March I6, 1922.
The Atomic Process in Ferromagnetic Induction. S~R J. A. EWING. (Proc. Royal Society, A 7o6.)--In 189o the author brought to attention a model which embodied his conception of ferromagnetic ivduction. In one plane it consisted of a group of similar, pivoted magnets. When no external magnetic force acts, these form configurations under the influence of their mutual attractions and repulsions, and when an external force is brought into action, as by the insertion of the group of magnets into a magnetizing coil, it is their mutual forces which must be overcome before the magnets can turn into the direction of the applied magnetizing force. Such a model simulated many of the phenomena manifested when a piece of iron is magnetized and, indeed, with striking completeness. Professor Ewing, however, finds that there is a great discrepancy between the magnetizing force really needed to make iron pass from the reversible to the irreversible stage and that which would be needed to accomplish the same change were the elementary magnets subject alone to their mutual attractions. He finds it necessary to place near each pivoted magnet two pairs of permanent magnets. Each pair has poles arranged thus, N S-S N and the axes of both magnets lie in the same line, but the directions of these lines are different for the two pairs. The pivoted magnet can turn within the magnets forming a pair without touching either. There is assumed to be a slight dissymmetry in the strength or in the position of the two magnets in the same line. When it comes to seeking in the actual atom something akin to this highly artificial arrangement, it is suggested that a pair of electrons on opposite sides of the nucleus of the atom may correspond to the pivoted magnet, while groups of electrons farther away from the centre may play the r61e of the fixed magnets. The new type of model is far removed from the simplicity of its predecessors of 189o ,
656
CURRENT TOPICS.
[J. F. I.
which did so much to clarify magnetic conceptions when hysteresis was a new thing. Magnetism is, however, in itself no simple matter and investigation seems to increase the number of prol)lems awaiting solution rather than to furnish a clue to already existing difficulties. It would therefore appear that a complex model is needed to represent complex effects and surely no one is better fitted to make fruitful suggestions in this field than one who has already succeeded eminently. G. F. S.
A New Hydrogen P r o c e s s . - - M u c h attention has been paid of late years to methods of obtaining hydrogen, principally on account of its use in the treatment of fats and for the inflating of dirigibles. It has also some applications as a reducing agent and as fuel. The use of ferrosilicon in solution of sodium hydroxide is one of more recent methods, which is described in a paper bv E. R. \Veaver, presented at the forty-first meeting of the American Electrochemical Society in April last. Although more expensive than other processes, it is suitable for military use on account of the small cost of the plant and the simplicity of operation. The reaction is between the silicon and the alkali, and the principal equation is 2NaHO + Si + H~0 = Na._.Si0:, + 2H~. This represents the change at the beginning of the operation, but secondary reactions occur by the hydrolysis of the sodium silicate. The temperature must be controlled during the process. The facts that none of the materials used are combustible, that they do not give off any gas until mixed, and are easily transportahle, are especially advantageous in naval operations. The gas produced is of high purity, traces of phosphine and acetylene being the principal impurities, although hydrocarbons and even arsine may occur. The disposal of the exhausted liquor is, however, a serious matter, as it is too alkaline to be thrown into a running stream. H.L. L a t e n t H e a t of Fusion. MRS. K2. STRATTON and J. R. PARTINGTON. (Phil. Ma9., March, I 9 2 2 . ) - - T h e method seems to be new. A known mass of solid is maintained at its melting point by being surrounded by a mixture of the solid and liquid phases of the same substance. H e a t is then imparted to the mass by sending an electric current through a resistance coil. This is continued until all the solid has just turned into liquid. O f course adequate stirring is provided. F r o m the energy added and the mass of the solid it is easy to calculate the latent heat of fusion. In the case of benzophenone three separate experiments gave these values for the specific heat, 21.64, 21.79 and 21.58 calories per gram. An attempt was made to get the latent heat of rhombic sulphur, but it failed owing to the transformation into the monoclinic variety that occurred during the course of the experiment. G.F.S.
METHOD OF CALCULATING FLUIDITY.
655
latter can be calculated over a range corresponding to the range of the known values for the first substance ( B ) . • To do this, the values of the ratio T A / T B = R are plotted against the absolute temperatures T~ and a straight line drawn through the points. By multiplying a particular temperature, T~ , by the corresponding temperature ratio (read off from the curve), the absolute temperature, TA, is obtained at which the value of the physical constant of the substance d is equal to that of the substance B at the absolute temperature T~. I f the line does not run through the points (i.e., if c is not constant), it is probable that the experimental data are not accurate, or that one of the substances behaves abnormally. S WARTHMORE, PA.,
March I6, 1922.
The Atomic Process in Ferromagnetic Induction. S~R J. A. EWING. (Proc. Royal Society, A 7o6.)--In 189o the author brought to attention a model which embodied his conception of ferromagnetic ivduction. In one plane it consisted of a group of similar, pivoted magnets. When no external magnetic force acts, these form configurations under the influence of their mutual attractions and repulsions, and when an external force is brought into action, as by the insertion of the group of magnets into a magnetizing coil, it is their mutual forces which must be overcome before the magnets can turn into the direction of the applied magnetizing force. Such a model simulated many of the phenomena manifested when a piece of iron is magnetized and, indeed, with striking completeness. Professor Ewing, however, finds that there is a great discrepancy between the magnetizing force really needed to make iron pass from the reversible to the irreversible stage and that which would be needed to accomplish the same change were the elementary magnets subject alone to their mutual attractions. He finds it necessary to place near each pivoted magnet two pairs of permanent magnets. Each pair has poles arranged thus, N S-S N and the axes of both magnets lie in the same line, but the directions of these lines are different for the two pairs. The pivoted magnet can turn within the magnets forming a pair without touching either. There is assumed to be a slight dissymmetry in the strength or in the position of the two magnets in the same line. When it comes to seeking in the actual atom something akin to this highly artificial arrangement, it is suggested that a pair of electrons on opposite sides of the nucleus of the atom may correspond to the pivoted magnet, while groups of electrons farther away from the centre may play the r61e of the fixed magnets. The new type of model is far removed from the simplicity of its predecessors of 189o ,
656
CURRENT TOPICS.
[J. F. I.
which did so much to clarify magnetic conceptions when hysteresis was a new thing. Magnetism is, however, in itself no simple matter and investigation seems to increase the number of prol)lems awaiting solution rather than to furnish a clue to already existing difficulties. It would therefore appear that a complex model is needed to represent complex effects and surely no one is better fitted to make fruitful suggestions in this field than one who has already succeeded eminently. G. F. S.
A New Hydrogen P r o c e s s . - - M u c h attention has been paid of late years to methods of obtaining hydrogen, principally on account of its use in the treatment of fats and for the inflating of dirigibles. It has also some applications as a reducing agent and as fuel. The use of ferrosilicon in solution of sodium hydroxide is one of more recent methods, which is described in a paper bv E. R. \Veaver, presented at the forty-first meeting of the American Electrochemical Society in April last. Although more expensive than other processes, it is suitable for military use on account of the small cost of the plant and the simplicity of operation. The reaction is between the silicon and the alkali, and the principal equation is 2NaHO + Si + H~0 = Na._.Si0:, + 2H~. This represents the change at the beginning of the operation, but secondary reactions occur by the hydrolysis of the sodium silicate. The temperature must be controlled during the process. The facts that none of the materials used are combustible, that they do not give off any gas until mixed, and are easily transportahle, are especially advantageous in naval operations. The gas produced is of high purity, traces of phosphine and acetylene being the principal impurities, although hydrocarbons and even arsine may occur. The disposal of the exhausted liquor is, however, a serious matter, as it is too alkaline to be thrown into a running stream. H.L. L a t e n t H e a t of Fusion. MRS. K2. STRATTON and J. R. PARTINGTON. (Phil. Ma9., March, I 9 2 2 . ) - - T h e method seems to be new. A known mass of solid is maintained at its melting point by being surrounded by a mixture of the solid and liquid phases of the same substance. H e a t is then imparted to the mass by sending an electric current through a resistance coil. This is continued until all the solid has just turned into liquid. O f course adequate stirring is provided. F r o m the energy added and the mass of the solid it is easy to calculate the latent heat of fusion. In the case of benzophenone three separate experiments gave these values for the specific heat, 21.64, 21.79 and 21.58 calories per gram. An attempt was made to get the latent heat of rhombic sulphur, but it failed owing to the transformation into the monoclinic variety that occurred during the course of the experiment. G.F.S.