that are made on condensers is influenced by the use of an imperfect tinfoil contact. i. In connection with the measurement of the directcurrent conductivity of a condenser having tinfoil armatures, the experiments of Mr. Appleyard (Proc. Phys. Soc., 1905, xix., 724), in which the current a minute or two after the first switching on of the current was greater than that at the time of switching on, are referred to. These experiments go into the matter in more detail. By choosing a suitable dielectric-celluloid, which has a conduction current of a greater value than the rate of change of displacement current-it was found possible to greatly increase the magnitude of these secondary increases in current. At very low pressures there is very little increase of current, and moreover what little increase there is over in a few minutes, but as the pressure is increased the secondary increase gradually becomes larger and takes longer to attain its maximum value. The maximum effect was reached at about 750 grms./sq. cm., when the increase of current amounted to 40 per cent, and the time required five and a-half hours. At very large pressures, when the contact becomes an intimate one, the increase of current becomes smaller again and the time required also smaller. If the pressure is left on and the voltage removed for some hours a repeat test follows the same course, the current starting at the same value and attaining the same maximum value. Voltage has, therefore, quite as much effect as pressure in bringing about an intimate contact, and acts independently of it. By considering the geometry of the tinfoil humps, an explanation of these various effects is given, and the different ways in which the pressure and the voltage increase the degree of contact between the dielectric and the tinfoil armatures are described. be applied. The tinfoil could be squeegeed on to the The Mr. R. APPLEYARD was glad Mr. Bairsto had adopted the direct reading method of examining the changes in dielectric resistance. The author had kept the current on till a steady deflection had been obtained. It was often more valuable to take the reading after a definite time, say, one minute. He did not think that the alternating current test in the second part of the paper had much bearing on the first part. The work on the residual charge was most interesting. Mr. E. H. RAYNER remarked that it was assumed by all workers on the subject that the properties of the dielectric itself were not directly influenced by pressure, whereas this might in itself decrease the resistance of the dielectric. He would like the author to carry out pressure experiments on a silvered celluloid condenser. Dr. A. RUSSELL agreed with the last speaker. Celluloid was far from homogeneous. The dielectric resistance was not a constant, but was a function of the applied voltage. Mr. G. L. ADDENBROOKE emphasised the effect of heating of the dielectric due to the energy loss in it. He also remarked that the author had neglected surface conduction. Mr. W. DUDDELL remarked that the paper showed the importance of a thin air film in the determination of the conductivity and capacity of a condenser. For standard condensers makers knew that if the air was not excluded the capacity would not remain constant. If a high voltage were applied to such a condenser and left on for some time the capacity afterwards would be found to be permanently altered. Even with as low a voltage as 200 volts we may get brush discharges into the air film. 2. While considerable errors are liable to be made in deducing the specific direct current conductivity of a dielectric between tinfoil armatures, the same is not true for measurements of the alternating-current conductivity. The influence of the bad contact is twofold. Firstly, it decreases the apparent capacity by inserting in series with the condenser under test a very large but still finite air condenser. This causes a decrease in the measured conductance. Secondly, because of the decrease in area of contact, it decreases the magnitude of that component of the conductivity which is independent of the frequency-curve as mercury electrodes. i.e., the purely ohmic conductivity. By considering the system as equivalent to a leaky condenser in series with a very large capacity due to the air film, expressions are deduced for the equivalent capacity, conductance, and power factor, and these expressions furnish us with the means of separating out the two above effects. It is shown experimentally, even under the worst possible circumstances, the dielectric being only lightly bound up with the interleaved tinfoil, that for telephonic frequencies the maximum difference between the observed conductivity and true conductivity is 15 per cent and of capacity is 5 per cent. With the condenser tightly bound with tape and wedges of wood inserted, the maximum difference was only 4'5 per cent in the conductivity and 2.5 per cent in the capacity. 3. Finally, the influence of imperfect contact upon the accumulation of residual charge is considered. It is shown that if we have a condenser with tinfoil armatures, as, for instance, tn the Franklin jar, with its rigid metallic coatings, the recovery of a residual charge is obscured by the presence of creeping surface charges coming out of the undischarged portions of the dielectric leading to an apparent residual charge much more than the true residual charge left in the dielectric. Dr. J. A. FLEMING thought the paper contained much valuable information. He emphasised the difficulty and importance of getting rid of the air film. For many dielectrics, such as glass or indiarubber, pressure could not Prof. C. H. LEES expressed his interest in the third section. He would like to know whether tinfoil electrodes under pressure would give the same residual discharge The AUTHOR, in reply to Prof. Lees, was sure it would give the same curve. A paper "On a Method of Measuring the Pressure of Radiation by means of Thin Metal Foil" was read by Mr. GILBERT D. WEST. The pressure of the radiation emitted by a carbon filamentl amp at a distance of a few centimetres is sufficient to cause a microscopically measurable deflection of the end of a suspended strip of gold or aluminium foil, and by this means the radiation pressure can be calculated knowing the weight of the strip. The results agree to within about 10 per cent with the energy content per cubic centimetre as measured by the initial rate of rise of temperature of a copper plate exposed to the radiation. The best results are obtained by working in an atmo sphere of hydrogen, 1 cm. to 2 cm. pressure, but good results are obtained with hydrogen at atmospheric pressure. Air at 1 cm. to 2 cm. pressure also gives good results. The method involves no laborious adjustments, and the apparatus is not seriously affected by vibration. Prof. C. H. LEES remarked that the point in the above paper was its extreme simplicity. Dr. C. W. C. BARLOW (in some remarks communicated, by Prof. Poynting) pointed out that the author ought to allow for the light reflected from the foil to the glass wall and back again to the foil. This would improve the agreement in the author's measurements. CHEMICAL NEWS, July, 4, 1913 Chemical Notices from Foreign Sources. II A paper "On the Emission of Electricity from Hot | from them; for example, the author has drawn attention Bodies and the Quantum Theory was read by Dr. W. WILSON. The paper gives a theory of the emission of electricity from hot bodies which is based on the quantum theory of energy. A formula connecting the thermionic current and the temperature of the emitting body is deduced. This formula closely resembles that of Richardson, and agrees slightly better with experimental results. Prof. J. W. NICHOLSON thought the paper was a valuable one in that it connected up yet another phenomenon with Planck's quantum theory of radiation. It was probable that Planck's constant h was in some way an electron constant, and that the emission of energy was discontinuous because emission of electrons was discontinuous. NOTICES OF BOOKS. Metallic Alloys. By G. H. GULLIVER, B.Sc., F.R.S.E., A.M.I.Mech. E., M.Inst. M. Second Edition. London: Charles Griffin and Co., Ltd. 1913. THE text of this book is based upon various courses of lectures on alloys given by the author at the University of Edinburgh and at the Heriot Watt College, Edinburgh. It gives a systematic and thoroughly scientific view of the structure and constitution of binary and tertiary alloys, as well as a short account of the methods of investigation employed, and of the use of the microscope in general engineering practice. The second edition has been very greatly enlarged, and many new microphotographs and equilibrium diagrams have been added, so that the illustrations now number over 300, while the references to current literature are almost as numerous. Organic Chemistry. By HOWARD D. HASKINS, A.B., M.D. Second Edition. New York: John Wiley and Sons. London: Chapman and Hall, Ltd. 1913. A COMPLETE survey of the facts of organic and physical chemistry which have an important bearing upon medical science is to be found in this book. The author has endeavoured to give a short description of every compound which should be known to the medical student, and the principles of physical chemistry are outlined. A course of practical work is described, including preparations, tests for purity, and methods of identification. A special feature of the text is the great number of structural formulæ given, with which the student is recommended to make himself thoroughly familiar. Nitrogenous Soil Constituents and their Bearing on Soil Fertility. By OSWALD SCHREINER and J. J. SKINNER. Washington: Government Printing Office. 1912. THIS Bulletin contains a detailed account of the effect on seedlings of the different nitrogenous soil constituents. The investigation proves that some compounds are beneficial, while others, which appear to occur normally in soils, are harmful. Thus picoline carboxyllic acid retards growth, and guanidine produces effects similar to those due to disease. All the culture experiments were carried out under strict chemical control, so that all possibility of the interference of bacterial influences was excluded. The Bulletin contains a complete summary of the effects of organic compounds of all classes upon the growth of various plants, including the results of many tests carried out in previous researches. Observaciones sobre el Método Crioscópico y Relaciones entre los Cuerpos Simples. ("Notes on the Cryoscopic Method and Relations between Simple Substances"). By CARLOS E. HEREDIA. Buenos Aires: A. Guidi Buffarini. In the first part of this thesis the results of many cryoscopic experiments are given, and some general inferences made to the fact that the maximum temperature of solidification is not necessarily equal to that of fusion. In the second part the question of the constitution of the elements is discussed and fundamental laws are formulated, showing how the chemical and physical nature of an element and also its type are functions of the atomic constitution which is a variable depending upon the degree of condensation of the atoms. The author expounds at length and with great intrepidity his views on force, energy, and matter, but does not appear to have made any material contribution towards the solution of the problem of their natures. CHEMICAL NOTICES FROM FOREIGN SOURCES. Comptes Rendus Hebdomadaires des Séances de l'Academie des Sciences. Vol. clvi., No. 14, April 7, 1913. Dehydration and Decomposition of Hydrates of Uranyl Nitrate.-M. de Forcrand.-When uranyl nitrate hexahydrate is dehydrated in the cold at atmospheric pressure two phases may be distinguished. During the first four or five days there is a tendency to form the trihydrate, and then when it is formed the loss of water becomes much slower, and stops completely when the dihydrate is reached. When the dihydrate is dehydrated at 98° in a current of CO2 a monohydrate is formed, containing less than 1 per cent of uranic acid. A practically anhydrous salt can be obtained by dehydrating the dihydrate at 165° in a current of CO2 containing nitrous vapours. New Double Sulphate of Cerium and Silver.-Emm. Pozzi-Escot.-When a warm sulphuric acid solution of cerium sulphate is treated with a warm solution of silver nitrate an orange-yellow crystalline precipitate of a double salt is obtained. When it is washed and dried and the excess of sulphuric acid is removed by heating it to 400°, it is found that its composition corresponds to the formula 10Ce(SO4)2.6Ag2.SO4. The anhydrous double salt is slightly soluble in cold water; when boiled with water it readily dissolves, undergoing decomposition. Solubility of Thorium Oxalate.-A. Colani.—When thorium oxalate is dissolved in water containing at least 20 per cent of hydrochloric acid, chloro-oxalate is formed and oxalic acid is precipitated. The solubility of the oxalate in oxalic acid is less than in hydrochloric acid, and the solubility in the latter is greatly decreased by the presence of oxalic acid. Action of Monosodium Acetylene on Alcoholic Iodides. Preparation of True Acetylenic Hydrocarbons.-Paul Lebeau and Marius Picon.-Chloride and iodide of methyl react at -50° on a solution of monosodium acetylene in liquid ammonia and allylene is obtained, C2HNa+CH3I=NaI + CH3.C=CH. The yield is about 96 per cent. Normal hexine can be prepared similarly from normal butyl iodide. Catalytic Etherification in Dilute Solution. Preparation of Ethyl Acetate.-F. Bodroux.-The distillation of a mixture of acetic acid and propyl alcohol in presence of a concentrated aqueous solution of aluminium iodide leads to the formation of a large quantity of propyl acetate, and the production of this ether salt can only be attributed to the catalytic action of the dissolved salt. Ethyl acetate can be obtained from a mixture of ethyl alcohol and acetic acid if an aqueous solution of sulphuric acid is used as catalyst, and the proportion of organic acid etherified is greater the greater the concentration of the sulphuric acid in the aqueous solution. No. 15, April 14, 1913. Reduction of Magnesia by Aluminium.-Camille Matignon. To reduce magnesia an intimate mixture is made with aluminium powder, which has been freed from fat by repeated washings with benzine and ether, in the proportion of MgO to Al2. The mixture is pressed into | quantity dissolved is proportional to the square root of the tablets, and heated in an exhausted steel tube in a porcelain gas pressure. tube. At 1200° the magnesia is reduced and the mag. nesium is deposited in large crystals on the cooler part of the tube. The reduction is practically complete and constitutes a useful method of preparing magnesium. Aromatic Telluretin Compounds.-Karl Lederer.The methyl ether of bromacetic acid unites with diphenyl telluride to give a stable compound of formula (C6H5)2TeBr.CH2.COOCH3, corresponding to the sulphur compound (CH3)2SBICH2.COOH. The bromine atom can be replaced by chlorine, and a picrate of similar composition can be obtained. The ethyl ether of bromacetic acid also combines with diphenyl telluride, but the compound formed is less stable than the methyl compound. When silver oxide acts on the ester of diphenyl telluretin bromide the bromine atom is replaced by hydroxyl and the ester is saponified. Tetraphosphorus Trisulphide and a new Phosphorus Oxy-sulphide, P4S304.-Alfred Stock and Kurt Friederici.-Tetraphosphorus trisulphide is very stable in absence of air and moisture when the temperature is raised, and solid P4S3 is very stable towards air. When oxygen is led through a solution of P4S3 in carbon disulsulphide in absence of moisure a new oxidation product, It is a yellowish white heavy powder P4S3O4, is obtained. It is very readily which decomposes when heated. attacked by water, and gives a yellow solution with caustic soda. When ozone acts on P4S3 solutions, higher oxidatheir behaviour, but give a colourless solution with caustic These resemble P4S304 in tion products are obtained. soda. MISCELLANEOUS. Colour Reaction for Detection of Hyposulphites.Emm. Pozzi-Escot.-To test for hyposulphite in a solution an equal volume of 10 per cent ammonium molybdate is added, and 5 cc. of pure concentrated sulphuric acid are run in by means of a pipette. In presence of hyposulphite a blue coloration is produced at the zone of separation of the aqueous mixture and the acid. If the concentration Royal Society of Arts.-The Annual Meeting of the of the hyposulphite solution is greater than 1/5000, the blue Royal Society of Arts was held on Wednesday, June 25th, zone is preceded by a more or less yellowish green zone. Lord Sanderson, G.C.B. (Chairman of the Council), in It is possible by means of this reaction to detect the pre-of the Society during the past year was read. H.R.H. the Chair. The usual Report recording the Proceedings sence of 0.00005 grm. of sodium hyposulphite. Determination of Iodine in Iodotannic Syrup.Emm. Pozzi-Escot.-A simple and rapid method of determining iodine in iodotannic syrup is as follows:-Twenty five cc. of the syrup are diluted with 50 cc. of water. Ten cc. of chloroform or carbon disulphide are added, then 2 cc. of concentrated sulphuric acid and an excess of a saturated solution of potassium permanganate. The iodine is thus liberated, and dissolves in the organic solvent, and may be determined by means of a titrated solution of sodium hyposulphite. Solubility of Certain Metallic Salts of Volatile Fatty Acids in Organic Solvents.-Henri Agulhon.If the copper salt of an organic acid is produced in an aqueous medium by double decomposition, and the liquid is then shaken with certain organic solvents, the latter in certain cases extract all or part of the copper salt formed. The amount extracted is a function of the molecular weight of the acid used. Thus, whatever the solvent none of the salt is extracted in the case of formic or acetic acids. With propionate a light blue coloration appears in acetic ether, the aqueous solution remaining deeply coloured. In the case of butyrate an intense blue coloration is produced with acetic ether, ether, chloroform, amyl alcohol, while the aqueous solution becomes colourless. Berichte der Deutschen Chemischen Gesellschaft. Vapour Pressure of Liquid Tin Amalgams containing Small Amounts of Mercury.-A. Sieverts and H. Oehme. The vapour pressures of liquid tin amalgams containing from 0.8 to 8 per cent of mercury are nearly proportional to the concentration of the dissolved mercury between 300° and 360°, and for pressures from 2–70 mm. Hg. Two single series of experiments with 2 and 10 per cent Hg gave the same result for 515° and 528°, and a pressure interval of 173-886 mm. Hg. Thus the solution of monatomic mercury vapour in liquid tin follows Henry's Law, while in the solution of diatomic gases in metals the the Duke of Connaught was re-elected President, with the usual number of Vice-Presidents and Council. Thirty-five new Members were elected, making a total of 238 elected during the Session, the 159th of the Society. Royal Society of Arts.-Award of Medals.-The Dr. F. Mollwo Perkin- " Natural and Joseph Pennell-"The Pictorial Possibilities of Work." E. Russell Burdon, M.A.-"The Development of Frank Bailey, M.Inst.C.E.-" Electric Supply in Walter C. Hancock, B.A., F.I.C.-"The Physical Pro- H. V. Lanchester, F.R.I.B.A. "The Design and F. G. Ogilvie, C.B., LL.D.-"The Science Museum." J. Forrest Brunton-"The City of Karachi.” W. H. Warren, LL.D., M. Inst.C.E., M.Am. Soc.C.E., C. E. W. Bean, M.A., B.C.L.-"The Wool Industry The Right Hon. Sir Joseph George Ward, Bart., "NIVOC" PATENT FLEXIBLE STENCIL, No. 1. Full details on application. F. E. BECKER & CO., 17-27, HATTON WALL, E.C. MICA A. Telephone No. 2248 Avenue. P. WIGGINS & SONS, 102/3/4, Minories, London, E. MICA MERCHANTS, Manufacturers of Mica Goods for Electrical and ALL purposes. Contractors to His Majesty's Government. Cloth, 316; Paper covers, 216. (Postage, 4d. extra). THE WHEAT PROBLEM: Based on Remarks made in the Presidential Address to the British Association at Bristol in 1898. REVISED WITH AN ANSWER TO VARIOUS CRITICS By SIR WILLIAM CROOKES, F.R.S. 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Journal of the Royal Society of Arts, May 23, 1913. "In indexing articles, the spelling and nomenclature originally adopted by the authors has been adhered to. . . So far as has been noticed, this is the one blot on an excellently planned and finely executed work of a monumental character."-Journal of the Society of Dyers and Colourists, June, 1913. The Index under review is one that will be necessary to every reader of the Chemical News, and, indeed, will be useful to all chemists, giving, as it does, references to so many subjects, such as university intelligence, &c., which are found in perhaps no other chemical journal."-Nature, June 19, 1913. Orders should be sent to CHEMICAL NEWS, 16, NEWCASTLE STREET, FARRINGDON STREET, LONDON, E.C. PORCELAIN HALDENWANGER Can be obtained from all businesses which deal in Chemical Apparatus. London: Printed and Published for the Proprietor by EDWIN JOHN DAVEY, at the Office, 16, Newcastle Street, Farringdon Street, B.C. July 4, 1913. |