CHEMICAL NEWS, May 2, 1913 Chemical Notices from Foreign Sources. Prof. W. W. Haldane Gee, M.Sc.Tech., B.Sc. (Manchester), delivered a Lecture, illustrated by experiments and lantern slides, on "The Electrolytic Methods for Preventing the Corrosion of Metals." 215 The overvoltage of a metal was taken as the difference between the back E.M.F. set up after an application of the polarising current for thirty minutes at a given current density, in N/10 acid, and that set up by the above electrode under similar conditions. It is probable that overvoltage is simply a manifestation of the difference between the rate of production of ions at the electrode and of the combination of these to form complexes. Probably after being discharged the ions pass into a metastable condition and give rise to a back E.M.F. The catalytic activity of the electrode is probably an important factor as affecting this velocity of reaction, and the difference in catalytic activity of various metals under different conditions of texture, temperature, &c., would explain why the overvoltage varies largely with different metals under different conditions. Overvoltage may be of importance in the case of the corrosion of a metal as either (a) Having a tendency to retard the deposition of hydrogen or oxygen on its surface, which might tend to assist or prevent corrosion. (b) By setting up a high back E.M.F. which would diminish the effect of a decomposing current in cases of corrosion due to electrolysis. (c) By assisting or preventing the solution of a meta'. The condition that a metal may dissolve in an acid and evolve hydrogen is given by the relation E.M.F. of metal back E.M.F. of hydrogen>ŋ; waere = overvoltage of metal. If is large, no solution of the metal can occur. This is apparent with galvanised iron, where, owing to the overvoltage of the zinc, very little solution of iron takes place, the latter assuming the overvoltage of the external metal. He showed that the corrosion of metals can be lessened or prevented in two ways (1) By connecting the metal to be protected to a more electro-positive metal, so that a primary cell is produced; (2) by making the metal to be protected the cathode in an electrolytic cell supplied by an external electrical pressure. Various types of primary cell arrangements that could be employed in practice were classified. The efficiency of the cell for protection will depend on the current density at the cathode, and this will be controlled by the resistance of the cell and the effective voltage. The importance of overvoltage in determining the effective voltage was discussed. The history of Sir Humphry Davy's application of zinc and iron protection for the prevention of the corrosion of the copper sheathing of ships and subsequent inventions for the protection of condensers and pipes were detailed. The patents of Harris and Anderson, in which aluminium alloys are used for the prevention of the corrosion of condenser tubes, were shown to be primary cell methods. In the case of the use of zinc in boilers was involved a knowledge of the electrolytic resistance of the boiler waters and the effective voltage at temperatures from 150-200° C., concerning which there is great need of experimental data. The amount of zinc used in some marine boilers is as great as from 400-600 lbs. of rolled zinc per annum. If the zinc is efficient in producing electrical currents then the average current may be from 17 to 25 ampères. It was obvious that such currents would be obtained much more economically by the use of a dynamo. The direct use of electrical currents has been the basis of a number of patents. Those of Mr. Elliott Cumberland were especially described. Iron anodes are placed in the water of the boiler, which latter is made the cathode. A low voltage of supply provided by a small motor-generator is used. The method has proved effective not only in preventing corrosion, but also in removing scale from the heating surface and preventing its formation. Experiments carried out at the Manchester School of Technology have shown that the current densities necessary to protect iron, copper, and other metals from the corrosion of fresh and salt water are of low value, and hence in the cases of boilers and condensers the annual cost of the electrical energy required is a small item. The chief cost will be in the renewal of anodes. Harris and Anderson have also applied, electrical currents for the CHEMICAL prevention of the corrosion of condensers. They find that a condenser with a cooling surface of 1025 sq. ft. requires only 2 volts and 2 ampères, and the special anodes used by them cost fro.n £3 5s. per 1000 sq. ft. per annum. The use of electrical currents may also be applied in chemical works to prevent the corrosion of metallic screens and vessels from acid liquids. Mr. J. T. CRABTREE, M.Sc., read a paper on "The Nature of Overvoltage." This may be regarded either as the excess of the anodic or cathodic decomposition voltage of a dilute acid with a given electrode over that for platinised platinum, or as the excess of the back E. M.F. set up as an electrode (anode or cathode) after polarisation over that set up by a platinised platinum plate under identical conditions. This back E.M.F. was determined by alternately polarising an electrode and measuring its single potential difference by means of a potentiometer, alternate connection between the latter and the primary circuit being made by means of a rotating commutator. Overvoltage is affected by the time of application and current density of the polarising current, the nature of the electrolyte and electrode employed, and by the thickness of the latter. Since these factors also affect the back E.M.F. of platinum, a comparison electrode was employed onsisting of a thin deposit of platinum on Jena glass, the ack E.M.F. of which is constant with time. In view of the absence of any suitable factor to indicate the tendency of a metal to corrode, future experiments may indicate a parallelism between the overvoltage of a metal and its corrosion factor. Dr. W. ROSENHAIN, F.R.S., read a paper entitled "Note on a Specimen of Ancient Irow from Ceylon." The reading of the papers was followed by a long dis cussion. A number of specimens of corroded metals was exhibited. NOTICES FROM FOREIGN NOTE. All degrees of temperature are Centigrade unless otherwise expressed. Comptes Rendus Hebdomadaires des Seances de l'Academie It turns Decomposition of Water by a-Rays.-William Duane and Otto Scheuer.-The a-rays decompose water, whatever its state, into hydrogen and oxygen. In the solid state at -183° the product is detonating gas, while in the liquid state excess of hydrogen is formed, the oxygen | TUESDAY, 6th.-Royal Institution, 3. peroxide. In the gaseous state, also, excess of hydrogen WEDNESDAY, occurs. Catalytic Hydrogenation of Camphorone.-Marcel Godchot and Felix Taboury.-When camphorone is subjected to the action of hydrogen and reduced nickel at 130° it is transformed quantitatively into dihydrocamphorone, boiling at 182-183. At 280° camphorone and dihydrocamphorone are both converted by nickel and hydrogen into 1-methyl-3-isopropyl-cyclopentane. When organo magnesium compounds act on dihydrocamphorone the two isomeric hydrocarbons are obtained which are derived from it by dehydration, and which, when hydrogenated at 180° over nickel, give the corresponding saturated hydrocarbon. Case of Dimorphism.-A. Duffour.-When benzoyl vanillic alcohol is obtained by hydrogenating vanilline benzoate by means of hydrogen in presence of platinum black it forms triclinic crystals, while monoclinic crystals of the same chemical compound are obtained when a molecule of benzoyl chloride acts on a molecule of sodium vanillic alcoholate. All attempts to convert the one type of crystals into the other failed, but probably only the triclinic variety is stable, the monoclinic form existing in a state of false equilibrium. MISCELLANEOUS. Institute of Chemistry.-Pass List: March—April Examinations. Of eleven candidates who presented them. selves for the Intermediate Examination of the Institute, seven passed:-J. D. S. Bramer; L. F. le Brocq, B.Sc. (Lond.); L. Davis, B.Sc. (Lond.); G. A. Stokes; S. H. Stroud; H. Trickett; and E. G. G. Wheeler. Of twentyfive candidates who presented themselves for the Final Examination, fourteen passed. In the Branch of Mineral Chemistry S. C. Bate, B.Sc. (Lond.); F. G. Crosse; and S. G. Greene. In the Branch of Metallurgical Chemistry-E. Marsden. In the Branch of Organic Chemistry-W. F. Hollely; T. S. Jones, B.Sc. (Lond.); H. Lambourne. B.Sc. (Lond.); D. H. Peacock, B.Sc. (Lond.). B.A. (Cantab.); and F. Sproxton, B.Sc. (Lond.). In the Branch of the Chemistry of Food and Drugs, and of Water-A. L. Davidson; R. E. Griffiths, B.Sc. (Lond.); F. W. Hoyland; W. G. Saunders; and W. A. Storey. Royal Institution.-On Thursday next, May 8th, at "Recent Physiological In quiries-Equilibrium and the Sixth Sense," by Prof. 7th.-Royal Society of Arts, 8. W. Stirling, M.D., &c. "Life Saving at Sea," by Axel Welin, Assoc. Inst. N.A. Society of Public Analysts, 8. "New Apparatus for Maintaining Constant Temperatures," by F. H. and P. V. Dupré. "Proportionate Determination of Cocoanut Oil and Palm Kernel Oil in Mixtures," by H. R. Burnett and C. Revis. "Composition of Milk," by H. Droop Richmond. "Examination of the Oils from Manihot ceara and Funtumia elastica and a Comparison of their Properties with those of Linseed and Hevea Oils," by S. Rideal and L. H. D. Acland. "Recovery of Iodine from Residues," by H. W. Gill. Faraday Society, 8. "Re-determination of the Elastic Modulus of Aluminium,” and “Density of Aluminium," by F. J. Brislee. "The Potential due to Liquid Contact" (Part III) and "Electrolytic Determination of Copper in Solutions containing Nitric Acid," by Elizabeth Gilchrist and A. C. Cumming. "New Experiments on Col. loids," by T. A. Coward. Overvoltage," by J. W. Richards. THURSDAY, 8th.-Royal Institution, 3. "Florentine Tragedies-The Exile of Dante," by E. Armstrong, M.A. Royal Society. "Various Inclinations of the Electrical Axis of the Human Heart," by A. D. Waller. "Trypanosome Diseases of Domestic Animals in Nyasaland-Part III., Trypanosoma pecorum," by Surgeon-General Sir D. Bruce, Majors D. Harvey and A. E. Hamerton, and Lady Bruce. "Excystation of Colpoda cucullis from its Resting Cysts and the Nature and Properties of the Cyst Membranes," by T Goodey. "Experimental Hybridisation of Echinoids," by C. Shearer, W. De Morgan, and H. M. Fuchs. "Action of Radium Rays upon the Cells of Jensen's Rat Sarcoma," by S. Russ and Helen Chambers. FRIDAY, 9th.-Royal Institution, 9. "Life History of a Water Beetle," by F. Balfour Browne, M.A. SATURDAY, 10th.-Royal Institution, 3. "Humphrey Internal Combustion Pumps," by H. A. Humphrey, M.Inst.C.E. Biochemical Society. 4. (In the Physiological Laboratory, Cambridge). NOTES AND QUERIES. 3 o'clock, Mr. Edward Armstrong delivers the first of two THE SIR JOHN CASS ectures at the Royal Institution on " Florentine Tragedies," (1) "The Exile of Dante," (2) "The Burning of Savonarola"; and on Saturday, May roth, Mr. H. A. Humphrey begins a course of two lectures on Humphrey Internal Combustion Pumps." The Friday Evening Discourse on May 9th will be delivered by Mr. Frank Balfour Browne on "The Life History of a Water Beetle"; and on May 16th, by Captain Cecil G. Rawling, on "The Pygmies of New Guinea." TECHNICAL INSTITUTE, JEWRY STREET, ALDGATE, E.C. Principal-CHARLES A. KEANE, D.Sc., Ph.D., F.I.C. DEPARTMENT OF FERMENTATION INDUSTRIES. THE CHEMISTRY AND TECHNOLOGY OF HOPS. A Course of Five Lectures on this subject arranged for Brewers, Hop Growers, Hop Merchants, and others who are interested in Hops from the commercial point of view, will be given by Mr. A. CHASTON CHAPMAN, F.I.C. The Course will include a full description of the more important chemical constituents of the Hop, and a review of the present state of our knowledge in regard to their precise technological significance. An attempt will be made to indicate to the grower and merchant the nature of the Brewer's requirements, and to the Brewer the considerations which should exercise the greatest influence upon his judgment when buying. The Lectures will be held on TUESDAY afternoons at 5 30 p.m., commencing TUESDAY, MAY 20th, 1913. Detailed SYLLABUS of the Courses may be had upon application at the Office of the Institute or by letter to the PRINCIPAL. All the more ordinary forms of glass apparatus are now obtainable in QUARTZ GLASS. Illustrated Catalogue and a sample of Quartz Glass tube will be sent free on application. The above illustration gives an idea of the class of work produced any complicated design can be reproduced in Quartz Glass. GRAND PRIX, Almost The SILICA SYNDICATE, Ltd., 82, Hatton Garden, LONDON, E.C. May 1913 FREDK. JACKSON & CO., Ltd., 14, CROSS STREET, MANCHESTER. GENERAL CHEMICAL APPARATUS. HEMPEL and ORSAT GAS ANALYSIS THE LONDON GAS REFEREES' GAS BURETTES OF VARIOUS KINDS. ORSAT GAS ANALYSIS APPARATUS. ILLUSTRATED PRICE LISTS FREE ON APPLICATION. SPECIAL NOTICE. NOW READY. GENERAL INDEX TO THE CHEMICAL NEWS, Vols. 1 to 100 (1860 to 1909). Price £2. (Carriage extra). To make sure of securing a copy, orders should be sent immediately, to "General Index," 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, E.C. May 2, 1913. Edited by AND JOURNAL OF PHYSICAL SCIENCE Sir Wm. Crookes, O.M., F.R.S.] (WITH WHICH IS INCORPORATED THE "CHEMICAL GAZETTE"). Establish Sixty-eight Years. Published Weekly. Annual Subscription free by post £1. Entered at the New York Post Office as Second Class Mail Matter LEAD ASHES, SULPHATE OF LEAD, FOR SALE.-Sartorius Chemical Balance, 200 grms. to one-tenth mgrm., nearly new, with weights, &c. Also Fume Cupboard (small), Copper Ovens, and other Apparatus; in excellent condition.-Address, "Silex," CHE ICAL NEWS Office, 16, Newcastle Street, Farringdon Street, London, E.C. BRADY & MARTIN, LTD. Northumberland Road, Newcastle-on-Tyne. Victoria Bridge, Manchester. CATALOGUES ON APPLICATION. PLATINUM CRUCIBLES, UTENSILS, FOILS Bought at Highest Prices. THE LONDON REFINING CO., Ltd., 32, CLERKENWELL ROAD, LONDON, E.O. Bankers: LON., CITY, & MID. Telephone: 388 HOLBORN. BROTHERTON & CO., Ltd. AMMONIA |