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For further particulars apply to the Honorary Secretary, Mr. SIJIL ABDUL-ALI, 26, Bramshill Gardens, Dartmouth Park, London, N.W. GENERAL INDEX TO THE CHEMICAL NEWS (Vols. 1 to 100). REDUCTION OF PRICE. IN order to dispose of the remainder of the unsold stock, we have decided to offer the few remaining copies in hand at the greatly reduced price of £1. Orders should be sent to the MANAGER, CHEMICAL NEWS, 16, NEWCASTLE STREET, FARRINGDON STREET, LONDON, E.C. London Printed and Published for the Proprietor by EDWIN JOHN DAVEY at the Office 16, Newcastle Street, Farringdon Street, E.C. January 14, 1916 Edited by Γ Estab.ished Sixty-nine Years. Si, Wm. Crookes, O.M., Pres.R S. (WITH WHICH IS INCORPORATED THE "CHEMICAL GAZETTE"). Vol. 113.-No. 2930. served ARTICLES: CONTENTS. Friday, January 21, 1916 Fixation of Atmospheric Nitrogen, by L. L. Summers........ Permanganate Determination of Iron in the presence of Fluorides -the Analysis of Silicates and Carbonates for their Ferrous Iron Content, by O. L. Barnebey On the Combination of Protein with Halogen Acids, by J. H. Long and Mary Huil PAGE 25 27 28 Physical and Mechanical Factors in Corrosion, by C. H. Desch. 30 The Relative Corrodibilities of Iron and Steel, by J. Newton Friend..... NOTICES OF Books ............. CORRESPONDENCE.-Preparation of Snlphuretted Hydrogen CHEMICAL NOTICES FROM FOREIGN SOURCES... MEETINGS FOR THE WEEK......... 33 35 36 36 36 CAPPER PASS & SON, LIM., BRISTOL, are Buyers of LEAD ASHES, SULPHATE OF LEAD, LEAD SLAGS, ANTIMONIAL LEAD COPPER MATTE, TIN ASHES, &c., ORES, DROSS, or RESIDUES containing TIN, COPPER, LEAD, and ANTIMONY. SULPHUROUS ACID and SULPHITES. Liquid SO, in Syphons, for Lectures, &c. PHOSPHORIC ACID and PHOSPHATES. CARAMELS & COLORINGS for all purposes. A. BOAKE, ROBERTS & CO. (LIMITED) Stratford, London, E. 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The Publisher of the CHEMICAL NEWS has obtained the required permission of the War Office, and he will forward copies direct from the Office to any neutral country on receipt of instructions. where k is a constant or coefficient to be determined for The Equilibrium Constant.-The chemical driving force for any reaction will continually diminish as the reaction approaches equilibrium, or the velocity of the reaction will diminish as equilibrium is approached, and when equilibrium is reached V will equal V' and Or, as the concentration or active mass in any reaction increases, the velocity coefficient increases, and for each change in equilibrium due to temperature change there is a definite concentration ratio represented by this equilibrium constant K. Partial Pressures. If the concentration of a given molecule is C and the collisions of the molecule are proportional to this concentration, if there are two molecules the collisions between the two similar molecules will be C times as great as one molecule, or C2. As the total pressure of a mixture of gases is the sum of the pressure of each gas, and by Avogadro's hypothesis the pressure is proportional to the number of molecu es in the given space, the concentrations, instead of being represented by grm.-molecules C, may be expressed as partial pressure p, and equilibrium will be represented by the ratio of the partial pressures of the gases. Thus two molecules of NO will have the pressure p2no, while pa and po may represent the pressure of the N and O. At equilibrium the constant K will then become þV = RT RT V = and for the work done between the limits of pressure and P we have where In is the natural logarithm. For the work done in A = RT In + RT In Pino But the first term represents the initial pressures or the van't Hoff has applied this type of fundamental equation to a wide range of reactions, and by means of the second law of thermodynamics has made it applicable to temperature and concentration changes in which the latent energy plays an important part, for in these reactions the product of the specific heat by the temperature no longer represents the heat transfer. van't Hoff's Fundamental Equation.-The second law of thermodyramics expresses the relation of A, the maximum work possible at a temperature T, and U, the decrease in energy of the system in relation to the ratio of change of A with the temperature T, the equation being Substituting in this the value of A and = Α RT in K, we have when both A and in K change with the temperature T effect a large amount of dissociation. In order to avoid this dissociation a rapid movement of the air through the arc or the arc through the air is desirable, and this in turn causes increased radiation and convection losses, so the maximum possible temperature of the arc is not obtained, and hence there are imposed very distinct limitations to the yield of NO. Haber and Koenig investigated the possibility of utilising Haber's Theory of Ionic and Electronic Collisions.lower temperatures in the arc to avoid dissociation by enclosing the arc in a water-cooled quartz tube, whereby moderate temperatures were preserved. In place of the molecular collisions we have assumed above as due to the thermodynamic condition of the gas, they used a vacuum and endeavoured to utilise the kinetic energy from the rapid motion of the ions and electrons liberated by the arc stream under these conditions. Haber considered it possible to increase the thermodynamic concentrations about 50 per cent. His tests indicated that using a temperature of 3000° C. it was possible to show 10 per cent concentrations of NO, which would correspond to a temperature under the thermodynamic equilibrium of 4300° C. Haber gives a table showing the effect of various mixtures of N and O when working with the increased mean free path of the molecules due to a vacuum of 100 mm. of mercury. In his work Haber prefers to use the square root of the equilibrium constant K we have used above, thus enabling the partial pressures of the resulting substances to be read direct, while the partial pressures of the ingredients are expressed as square roots of the pressures. Haber's table for a pressure of 100 mm. is as follows: Nernst's calculations of x or equilibrium volumes in per cent of NO, using air at temperature of 1500° T to 3200° T, are plotted in Fig. 1. The yields of NO per kilowatt hour obtained by Haber were unsatisfactory, and the complications of small watercooled tubes and working under a vacuum of 100 mm. have not justified commercially the higher concentrations of NO he obtained. Commercial Processes now in Use have Distinct Limitations. We may assume that up to the present the processes in commercial use are limited strictly by the thermodynamic equilibrium of the van't Hoff equation. As the volume of gases when working with low eoncentrations of NO are considerable, the radiation and convection losses as well as the transfer of sensible and latent heat from the arc to the gases lower very materially the temperature of the arcs, and the yields therefore indicate an average working temperature of 2200° C. to 2500" C., or concentrations of 15 per cent to 2 per cent NO when working with air. These theoretical limitations of the direct processes of forming NO have therefore led to many efforts to dissociate the nitrogen molecule by other means. Sources of Chemical Energy.-Naturally the sources of chemical energy have offered a most fruitful field, but, like the synthesis of carbon compounds, a considerable elevation of temperature is necessary before the chemical energy becomes effective enough to break the bond of the nitrogen molecule. At these elevated temperatures practically all elements or compounds which release sufficient energy to combine with nitrogen have a greater combining power for oxygen, so the processes cannot be conducted with air, but involve the separation of the nitrogen from the oxygen of the air as a preliminary step. The compounds of nitrogen thus formed do not therefore include |