possible. It had occurred to several people before the War that the heat in the coke shoud be utilised for the formation of water gas by passing steam through the hot coke. During the War it was possible to put these ideas into practice, and remarkable results in continuous-working vertical retorts were obtained. It became possible with steaming to obtain over 20,000 cubic feet of very serviceable gas per ton of coal instead of 12,000. It was further found that the water gas ascending the retort protected the hydrocarbions generated from the coal, and so gave a further increased make of gas and lighter tar oils. The development of this process is to increase the temperatures about the bottom of the retorts and to highly superheat the steam before it enters the retorts. Further, the hot waste gases from the plant are being passed through waste heat boilers and more than the quantity of steam required for steaming the retorts is obtained in return for a small extra capital expenditure and the cost of the power required to drive the fan on the outlet of the boilers. There is a distinct limit to the use of steam in vertical retorts. It is not economical beyond a certain point to force heat through a fireclay wall to a charge in the retort for the purpose of making water gas, and although by this means the total gasification of the carbon in the charge has been achieved, the heat and financial balance sheets show this to be uneconomical. This is undoubtedly the line of advance in gas works practice, but from a national viewpoint I object to the conveyance of the coal to the gas works, and the removal of the coke. The coal pit is the proper place to make gas and pipe lines are the proper means of conveying heat units from the coalfields to the centres of distribution. As far as oil is concerned, the vertical_retort gives better tar oil results than the horizontal retort. Carbonisation of coal in vertical retorts is really fractional destructive distillation. The products of distillation are drawn away as made and have to pass through no higher temperature than that at which they are evolved, whilst if water gas is made at the same time in the retort this process protects the hydrocarbons and gives a greater quantity of a lighter quality tar. NOTES. THE idea of distributing samples which has been a feature of so many trade exhibitions in the past is to be carried one step further by the International Advertising Exhibition at the White City towards the end of November. Not merely samples but wares drawn from actual stock have been gifted by manufacturers of advertised articles in such quantities that every visitor who pays the shilling entrance fee will receive something or other out of the free Lucky Dip. To show how heartily the manufacturers of advertised goods are co-operating to make a success of the exhibitionthe profits from which will go to charities- one AN amalgamation has been completed betwEED English Electric Supplies, Limited, and the Lamp and Supplies Department of Messrs. Siemens Brothers & Co., Limited, and as from November 1, 1920, the business will be carried on under the title of English Electric & Siemens Supplies, Limited. Registered Office: Brook House, 191 and 192, Tottenham Court Road, London, W.1. The Supplies Department with Showrooms and Stores at 38 and 39, Upper Thames Street, London, E.C.2 will be retained, and all orders and business in connection therewith will be dealt with from that address, as heretofore. The same staff will be retained both in London and the Branch Offices. The new company will carry on the business of both companies on the same lines as fortion of new electrical devices shortly to be placed merly, and with the same products, with the addion the market. All orders unexecuted, and all obligations entered into by English Electric Supplies, Limited, will be carried out by English Electric & Siemens Supplies, Limited. THE FUTURE OF WAGES AND PRICES.—The situation in many industries at the present moment is the cause of some anxiety among the public, and discussions are being raised as to underlying economic reasons and practicable remedies. In view of the fact that many conflicting opinions are being expressed, the Federation of British Industries has drawn up a statement on the "Future of Wages and Prices," pointing the way to the only course which, in its opinion, can lead to the solution of the difficulties which beset the nation. The chief heads of the statement comprise the effect of the war on prices, "real" value of wages, reduction of prices (two alternatives), deflation impossible, the importance of increased the illusion of Government price fixing, rapid output, the division of the product of industry, and world exhaustion. The F.B.I. regard the only effective means by which prices can be reduced and the real wages of labour improved to be by working the existing instruments of production at their maximum pressure, and so increasing as rapidly as possible the mass of commodities to be bought. Any attempt on the part of the workers to improve their conditions by ca' canny and similar methods not only fails in its object, but, by causing a rise in prices, actually reduces the purchasing power of their present wages. An increase in money wages may temporarily alter this state of affairs, but it cannot affect the final result. It is true that the workers in one trade may secure an improvement in their own position at the expense of the rest of the community, but if the wages in all trades are increased, this merely results in the re-establishment of the old value of wages at a correspondingly increased level of prices.-The Chemist and Druggist, October 16, 1920. CONSTABLE & COMPANY, LIMITED. A TREATISE OF ELECTRO-CHEMISTRY Edited by BERTRAM BLOUNT, F.I.C., etc. NOW READY. HE MANUFACTURE OF CHEMICALS BY ELECTROLYSIS OZONE. y A. H. Hale, B.Sc., F.I.C. Demy 8vo. Illustrated By E. K. Rideal, D.Sc., F.C.S. Demy 8vo. Illustrated 6/- net. 12/- net. Other Volumes in Preparation. AN INTRODUCTION TO THE STUDY OF PHYSICAL METALLURGY. Illustrated. 12/6 net. OUTLINES OF INDUSTRIAL CHEMISTRY. A Series of Text-Books Introductory to the Chemistry of the National Industries, AN INTRODUCTION TO THE STUDY Of fuel. THE CHEMISTRY8 OF DYEING AND BLEACHING OF By Julius Hubner, M.Sc., Tech., F.I.C. Demy 8vo. THE CHEMISTRY OF THE OIL INDUSTRIES. By J. E. Southcombe, M.Sc., F.C.S. Demy 8vo. IRON AND STEEL. By O. F. Hudson, M.Sc., and Guy D. Bengough, M.A., THE CHEMISTRY OF THE RUBBER INDUSTRY. CEMENT, CONCRETE AND BRICKS. 9/- net. By A. B. Searle. Demy 8vo. 10/6 net. Other Volumes in Preparation. A TEXT-BOOK OF THERMODYNAMICS. With special reference to Chemistry. By J. R. Partington, INDUSTRIAL CHEMISTRY. A Manual for Students and Manufacturers. 3rd Edition. Royal 8vo. Illustrated. Edited by Allen Rogers ELEMENTS OF INDUSTRIAL CHEMISTRY. Edited by Allen Rogers, specially prepared for students LABORATORY GUIDE OF INDUSTRIAL CHEMISTRY. THE HYDROGENATION OF OILS. By Carleton Ellis, S.B. New and revised edition. 36/- net. By Robert C. Frederick and Aquila Forster, Ph.D., M.Sc. THE THEORY AND USE OF INDICATORS. By E. B. R. Prideaux, M.A., D.Sc. Demy 8vo. 12/6 net. THE IDENTIFICATION OF ORGANIC COMPOUNDS. By G. B. Neave, M.A., D.Sc., and THE PROFESSION OF CHEMISTRY. By Richard B. Pilcher, Registrar and Secretary of the Institute WHAT INDUSTRY OWES TO CHEMICAL SCIENCE. By Richard B. Pilcher and Frank Butler- CONSTABLE & COMPANY LIMITED. 10 & 12 ORANGE STREET W.C.1. 1 ROYAL INSTITUTION.-A General Meeting of the Members of the Royal Institution was held on the 1st inst. Sir James Crichton-Browne, Treasurer and Vice-President, in the chair. The Secretary reported the deaths of Professor Armand Gautier, an Honorary Member, and of Professor John Perry, and resolutions of condolence with the relatives were passed. Commander R. B. Brooks and Mr. J. F. Dalton were elected Members. WE learn with regret from the Locomotive Department of the L. & N. W. Railway that Mr. Nov. 5, 1920 BY ORDER of the OFFICIAL RECEIVER IMPORTANT SALE OF BRITISH LETTERS PATENTS DYES AND OTHER CHEMICAL PRODUCTS C. J. Bowen Cooke, C.B. F., has died at Falmouth A LARGE NUMBER of British Patents after a short illness, in his 62nd year. o iginally owned by BADISCHE ANILIN & SODA FABRIK of Ludwigshafen on Rhine, FARBENFABRIKEN vorms: FRIEDR. BAYER & CO. of Leverkusen, ACTIENGESELLSCHAFT FUR ANILIN FABRIKATION of Berlin, Germany, and others, having become vested in the above-named Company the Official Receiver, as Liquidator, is desirous of disposing of them by private tender. The highest or any tender will not necessarily be accepted. PARTICULARS of the said Letters Patents may be obtained from the OFFICIAL RECEIVER IN COMPANIES LIQUIDATION, 33, Carey Street, Lincoln's Inn, London, W.C.2, or from Messrs. J. H. & J. Y. JOHNSON, Solicitors, 47, Lincoln's Inn Fields, London, W.C.2, to either of whom tenders on the annexed form must be sent on or before the 30th day of November, 1920. Dated this 28th day of October, 1920. Το FORM OF TENDER. The Official Receiver in Companies Liquidation. WE the undersigned hereby tender for the purchase of British Letters Patents Nos. for the sum of £ and undertake to execute a contract for the purpose of carrying this tender into full effect, such contract to be prepared by Messrs. J. H. & J. Y. Johnson, of 47, Lincoln's lon Fields, London, W.C.2, and to contain the covenants and conditions usual to such contracts, and we further agree that until such contract is executed this tender together with the acceptance thereof in writing shall be the contract. We are, Sir, Your obedient Servants, anions is most often unequal, inasmuch as one is present in excess nearest to the surface of contact, and the other in excess some way out in the liquid. The result is the formation of an electrical potential difference, a so-called adsorption potential difference or an elecetrical double-layer. Because COLLOIDS AND THEIR BEARING ON A SHORT SURVEY OF THE PHYSICS AND CHEMISTRY THE PHYSICS AND CHEMISTERSITY OF ILLINO BY DR. THE SVEDBERG, Professor of Physical Chemistry, (Concluded from p. 219.) Finally we will consider two phenomena, the study of which does not, it is true, enable us to carry out direct measurements of the structure, but which, in spite of that, are of great interest in judging of the structure of colloids, viz., the viscosity on the one hand, and, on the other, the adsorption and the accompanying phenomena, viz., the cataraphoresis and the electric endosmose. un The viscosity of a sol depends, in a manner not yet known, on the size of the particles, the concentration, &c., but above all on the nature of the particles. Some sols, e.g. metal hydrosols, suspensions of barium sulphate (Case 1) have a viscosity only slightly greater than that of water, but others, e.g. silicic acid hydrosol, oil emulsion, gelatin solution (Case 2) have a viscosity many times greater than that of water. From the fact that suspensions with undoubtedly solid particles come under Case 1 and emulsions with doubtedly fluid particles come under Case 2, the conclusion has been drawn that the fine-grained colloids under Case 1 also contain solid particles and those under Case 2 fluid ones. If this be the case, measurements of the viscosity would be a capital means of ascertaining the state of aggregation of the substance of the particles. Recent investigations indicate, however, that the case is far more complicated. Small particles probably have relatively thicker water-coverings than greater particles, and, accordingly, the viscosity is higher in a fine-grained colloid than in a coarser one, provided the two sols have particles of the same material and are of the same concentration by weight (e.g., sulphur hydrosols). When the potential difference between particles and fluid is. altered the thickness of the water-coverings should alter and, as a matter of fact, the viscosity is altered too. As the water-covering increases, the particle will act more and more like a drop of fluid in relation to the surrounding medium and will, therefore, as far as the viscosity is concerned, approach more and more to the limiting case which is represented by an oil emulsion. The phases-two or more in number-in a disperse system have a contact surface very large relatively to the volume of the system. It is obvious that in such circumstances adsorption plays a prominent rôle. The adsorption of different substances differs in strength. electrolytically-dissociated salt is adsorbed, cations and anions are, of course, brought together at the contact surface in equal numbers, but the adsorption of the particles in relation to cations and If an of this the disperse phase, when exposed to the influence of an electric field, will migrate towards one of the poles, provided it is freely movable, as in the case of a colloid solution (cataphoresis). If the disperse phase is immovable the liquid will move in the opposite direction (electrical endosmose). By measuring the velocity of migration of the particles or the liquid under various conditions we are able to study the changes in the difference of potential and thereby in the adsorption. At least at low concentrations the adsorption may be expressed by the formula y.=a. B where y is the amount of substance adsorbed per gr. adsorbent, e the concentration in the solution of the substance arsorbed, and a and 8 constants depending on the nature of both. Now, as a rule, it happens that for the two ions of a salt both a and have different values, e.g. a cation <a anion 8 cation >8 anion In the example chosen the disperse phase will with increasing adsorption become more and more negative in relation to the dispersion medium. This charge reaches a maximum and decreases to zero, at the point where the adsorption isotherms intersect, then becomes positive and increases again. The most The changes of state which may occur in a disperse system, a colloid, are essentially changes of structure. Of course, purely chemical reactions too, are to be taken into consideration, but they do not play such a prominent part here as in the molecular structural systems. The greater number of the disperse systems, and those of greatest importance too, are the ones whose disperse phase is embedded in the other phase in the form of particles; in the sequel we will only mention the changes of state in such systems. important change of state is the uniting together of the single particles (primary particles) into aggregates (secondary particles). Such an aggregation often occurs directly after the formation of the particles. It may stop for various reasons after the aggregates have reached a certain size. The result is a colloid with complex particles-a If the aggregation goes on secondary colloid. further we may have two extreme possibilitieswith many transition forms. First Case One or more of the following factors dominate, viz. : Second Case: One or more of the following factors dominate, viz. : (1) High hydration of the particles. (2) High number of particles per unit volume. (3) Small difference in specific gravity between particles and liquid. (4) No stirring of the system. In this case bridges are formed between the aggregates, and the particles arrange themselves into a three-dimensional network throughout the system the colloid gelatinizes (e.g. the coagulation of a sol of silicic acid by the addition of hydrochloric acid, the setting of a warm gelatin solution when cooling). Owing to capillary forces the liquid is kept in the network with great strength. Measurements have shown that the liquid is under a pressure of several hundred atmospheres. In many respects, therefore, the gelatinised colloid acts as a solid. There exist numerous transition forms between these two extreme cases If the particles are not bound together by bridges into a solid, but still reach macroscopical size and possess a certain loose structure, one speaks of flocculation of the colloid (e.g. coagulation of ferric hydroxide hydrosol by addition of ammonia). It may be doubted, however, if such flocculent suspensions are not to be regarded as fragments of a gel of little mechanical resistance shattered by the stirring of the liquid. Several observations support the view that there is in all colloids a certain tendency towards the formation of a network structure, the network being, however, in such systems as approach Case 1, very easily destroyed by movements in the liquid. In Case I the Brownian movements alone of the particles should suffice. The most important cause of the aggregation of the particles is the decrease or the disappearance of the difference of potential between particle and liquid. This may be effected by altering the ion adsoption. Hence one of the most important means of bringing about aggregation or disaggregation is addition or removal of ions. Because of the opposite electric and coagulating action of anion and cation and their difference of adsorption there will always exist, for certain electrolytes in relation to a certain colloid, a domain of concentration within which they have a disaggregating action. If a solely aggregating electrolyte is added to a colloid in increasing doses (e.g. hydrochloric acid to a gold hydrosol), the velocity of aggregation first rises rapidly with concentration, then more slowly and reaches a constant maximum value. Let us make the assumption that within the latter region every mutual approach of two particles to a certain limit leads to aggregation,but within the former region only a certain fraction of those approaches. Then it is possible to develop, on the basis of the laws of the Brownian movements alone, mathematical theory for the kinetic of aggregation. The formulæ for the decrease in the number of single particles (primary particles), and for that in the total number of particles (primary particles + aggregates) have been verified experimentally. a v=original number of particles. V1 = number of single particles after the time t. D= the diffusion constant. R=the distance to which the particles must approach if there is to be any aggregation. With regard to the aggregation by electrolytes it has, in addition, been found that inorganic ions of the same valency generally aggregate equally strongly if added in equivalent amounts. This is due to some extent to their being nearly equally strongly adsorbed. When the valency of the aggregating ion increases the aggregating effect rises very rapidly. The concentrations of the ions K. Ba Al required to aggregate particles of AsS, to the same degree show the mutual relations: 1, 1/20, 1/1000. Thus the three-valent Al· has an aggregating power 1000 times greater than the mono-valent K. These circumstances are closely related to the course of the adsorption isotherm, but are not yet quite clear. The aggregation may be reversible or irreversible, i.e., in certain cases disaggregation may be effected, in others not. Some colloids (e.g. metal hydrosols) are difficult to disaggregate, others (e.g. sulphur hydrosols) are easy. Certain ions nearly always bring about irreversible, others reversible aggregation. The question of irreversible or reversible coagulation is probably closely connected with that of the hydration of the particles. Thus particles which hold much water around them are easily disaggregated. The watercovering prevents the particles from uniting too closely together. The aggregating effect of an electrolyte may often be reduced to a very great extent by the addition of a small quantity of a suitable colloid of another kind only slightly sensitive to electrolytes, a so-called protective colloid, e.g. gelatin to a gold hydrosol. As a rule the electric charge of the protective colloid should be of the same sign as that of the colloid to be protected. The mechanism of this protecting action is still but very incompletely known. Most probably the particles of the protective colloid become attached to the particles of the other colloid and the aggregate resulting from this obtains a good deal of the stability towards electrolytes which characterises the protective colloid. Colloids of opposite electric charge precipitate each other mutually (e.g. the negative Sb,S, and the positive Fe,O,) provided there is not too great an excess of either of them, in which case no precipitation will occur. This is obviously entirely analogous to the action of the ions. Such mutual colloidal reactions are of great importance in the economy of nature and in industry. In the preparation of easily aggregated colloids a protective colloid is often added in order to maintain the primary structure. Thus the particles of a metal hydrosol, if formed in the |