JUN THE 1914 Property of Chemical Labor toru CHEMICAL NEWS AND JOURNAL OF PHYSICAL SCIENCE Edited by Established Sir Wm. Crookes, O.M., Pres.R.S.] (WITH WHICH IS INCORPORATED THE "CHEMICAL GAZETTE"). LEAD ASHES, SULPHATE OF LEAD, LEAD SLAGS, ANTIMONIAL LEAD, COPPER MATTE, TIN ASHES, &c., ORES, DROSS, or RESIDUES containing TIN, COPPER, LEAD, and ANTIMONY. Wanted, ASSISTANT in the County Chemi cal Laboratory. A good knowledge of Analyses of Foods and Drugs essential. Salary, £150 per annum. —- Three recent testimonials and one as to character should be sent to the COUNTY ANALYST, Shirehall, Worcester. FOR SALE-Beilstein's .6 Handbuch der Registered as [PRICE 41. The Proprietors of the PATENT No. 8528 of 1911, for "IMPROVEMENTS IN OR RELATING TO THE TREAT- are desirous of entering into arrangements by way of Licence and All communications to HASELTINE, LAKE, and CO., Chartered Patent Agents and Consulting Engineers, 28, SOUTHAMPTON BUILDINGS, CHANCERY LANE, LONDON, W.C. 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REVISED WITH AN ANSWER TO VARIOUS CRITICS By SIR WILLIAM CROOKES, F.R.S. SECOND EDITION. WITH PREFACE AND ADDITional chapter, bringing THE With Two Chapters on the Future Wheat Supply of the OPINIONS of the PRESS. "Sir William Crookes's statistics seem to make good his alarmist statement." - British Weekly. "In this bulky volume Sir William reproduces the gist of the sensational Bristol Address, and supplements it with carefully prepared answers to his chief critics and confirmatory chapters on the future wheat supply of the United States."-Morning Post. In Medium 8vo. Handsome Cloth. Pp. i-xii+340. With Plates and numerous other Illustrations. 188. net. A TEXT-BOOK ON TRADE WASTE WATERS, THEIR NATURE AND DISPOSAL. By H. MACLEAN WILSON, M.D, B.Sc., PURE CULTIVATION OF YEAST. Courses for beginners, as well as for Advanced Students in Physiology and Technology of Fermentations. Biological Analysis of Yeast. 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Of Gilt-lettered Covers for Binding the Half-year y CHEMICAL NEWS may now be obtained. Price1/6 each (post free 1/8). Volumes Bound 10 Cloth Cases, Lettered and Numbered at 25 td, per volume CHEMICAL NEWS OFFICE. IC, NEWCASTLE ST.. FARRINGDON ST., E.C. SULPHUROUS ACID and SULPHITES Liquid SO, in Syphons, for Lectures, &c. 2 PHOSPHORIC ACID and PHOSPHATES. CARAMELS & COLORINGS for all purposes. A. BOAKE, ROBERTS & CO. (LIMITED), Stratford, London, E. of water in this tube regulates the pressure of gas given by the apparatus. The air pressure forces acid through the wide tube (4) on to the sulphide (6), a layer of coarsely broken glass (5) acting as a rough filter. The gas is washed (7) and delivered at the tap (9) or stored in the vessels (8), from which the solution may be taken. A tap between 6 and 7 AN IMPROVED SULPHURETTED HYDROGEN may prove a convenience. APPARATUS. By FREDERIC WILLIAM RIXON. THE apparatus described below has undergone a severe test for six months; during that time it has worked most satisfactorily. It possesses certain advantages which will Renewal of acid follows by means of funnel (3) and tap (4). The whole apparatus may be readily fitted up from stock material, and admits of considerable variation to meet different requirements; for large laboratories it can be made to act automatically and deliver gas at a constant pressure, while if occasional supply only is required the apparatus will stand idle without losing efficiency. be equally appreciated in laboratories where sulphuretted hydrogen is used constantly or even very intermittently. Some of these advantages may be mentioned. A larger charge of iron sulphide may be used; the spent acid is easily replaced; when the apparatus is not in use the acid cannot possibly come into contact with the sulphide; the acid is totally enclosed; there is a reservoir of gas; gas and solution can be obtained, and the arrange. ment is practically fool proof. Description of Apparatus. Air pressure is obtained by using a filter pump (1) as a blower; too great pressure is relieved by the safety tube (2), which is of wide tubing sealed with water; the height The only replacement entailing a partial taking down o the apparatus is the refilling with sulphide. University of Bristol, April 30, 1914. Potassium Trioxide and the Stability of Alkaline Peroxides.-R. de Forcrand.-The heat of formation, starting from the elements, of the four alkaline trioxides, Na2O3, K203, Rb2O3, Cs2O3, is practically the same, viz., +126 cal. The passage from the monoxide to the dioxide disengages quantities of heat which regularly increase from calcium to cæsium :-Ca, 4'11; Li2, 7'97; Sr, 13:07; Ba, 18.36; Ra, 18.7; Naz, 1903; K2, 220; Rb2, 24'1; CS2, 250.-Comptes Rendus, clviii., No. 14 MOISTURE IN CLOTH. By WILLIAM M. DOHERTY, F.I.C., F.C.S. IN volume cviii. (August 22, 1913) of the CHEMICAL NEWS there appeared a short article by Mr. E. G. Bryant, B.A., B.Sc., of Port Elizabeth, South Africa, in which is noted the amounts of hygroscopic moisture found in woollen cloth at the above named locality, the said amounts being 12 per cent and 14 per cent respectively. A request for comparison with moisture content of a similar fabric in other parts of the world is expressed, the idea being to see if there are noted differences in "condition" produced by different geographical positions. The subject is perhaps an important one, and I give here my experiences in Sydney, New South Wales. Occasionally during a long period of years I have had to determine the moisture in ordinary woollen cloth, and the results always approximated 10 per cent, which I had considered the normal figure for this part of the world. But as the purpose for which my tests were made was to enable me to calculate analyses results on dry material simply, no notice was ever taken of humidity or temperature of air at the time of making the determinations. Since reading Mr. Bryant's article I have determined the hygroscopic moisture in various kinds of woollen fabrics, noting at the same time the relative humidity and also the temperature of the atmosphere. The method used in expelling the moisture was to heat in a water-oven (98° C.) until constant. results were as follow: Kind of fabric. The Moisture. Per cent. Relative humidity. Shade Temp. Per cent. °F. The degree of humidity seems here to exercise an influence on the moisture content, allowing for the apparent higher hygroscopic quality of the blanket. The amounts in Nos. 6 and 7 were the highest I had yet found, and I re-weighed the pieces after exposure to the air for some days, when the moisture was practically restored. But to obtain this latter result, final weighings had to be made following upon humidity and temperature being identical with those at initial weighings. A further test was made with a piece of high-class blue-back diagonal serge, which consisted of weighing the piece daily. simultaneously noting humidity and temperature. The results were: Relative humidity. 76 77 simple exposure. The above weighings were made of course under shade conditions wholly, and I found that if the same piece of cloth was exposed to the direct rays of the sun for three hours the weight had fallen to 8 64 grms., that is to say the greater part of the moisture had been expelled. A final experiment was made during the prevalence of very wet weather, the piece being weighed on a wet day after the rain had been falling more or less continuously for three days. The relative humidity at time of weighing was go per cent, and the temperature 77° F. The greatest previous weight was 9.214 grms., and it had now risen to 9'453 grms, an increase of 2.5 per cent. The total percentage of moisture in the cloth on this last occasion was 13.7, thus, during rainy weather, practically reaching the amount found by Mr. Bryant at Port Elizabeth. Ordinarily, then, the amount of hygroscopic moisture in cloth in Sydney is less than that found by Mr. Bryant Probably meteorologically the two in Port Elizabeth. ports are about on a par as far as this question is concerned. It should be noted perhaps that these experiments were made in February and March. Government Laboratory, Department of Public Health, Sydney, N.S.W. FLUIDS WITH VISIBLE MOLECULES. In a course of four lectures given recently at King's College, London, Prof. Jean Perrin, of the University of Paris, gave an interesting account of his work on the experimental verification of the molecular hypothesis. The kinetic theory of gases gives an approximate means of determining the actual dimensions of the molecule, and Maxwell obtained an expression for Avogadro's constant N, from considerations connected with the viscosity of gases. The Brownian movement of visible microscopic particles appears to be the result of molecular agitation, and any particle in suspension seems to function as an enormous molecule. If this is so, the gas laws, already extended by van't Hoff to solutions, must also apply to dilute emulsions composed of equal grains, and if the osmotic pressure of this. "gas with visible molecules" is known Avogadro's Law will give the ratio of the masses of the an indefinite vertical column of emulsion in equilibrium grains to those of the invisible molecule of any gas. In the osmotic pressure at any level counterbalances the weight of the higher layers, as in a heavy gas, and the emulsion is a miniature atmosphere. If, then, it is necessary to rise a hundred million times less than in oxygen in order to double the rarefaction, it may be concluded that the visible grain is a hundred million times heavier than the molecule of oxygen. In order to obtain equal grains emulsions made by precipitating alcoholic solutions of resin with water were submitted to a process of fractional centrifuga isation. These emulsions obey the gas laws, and the value of Avogadro's constant N can be calculated from them. It is found that the value of N thus found is independent of the size of the particles, and agrees with the number given approximately by the kinetic theory (68 x 1022). The Law of Gay Lussac holds good for temperatures between 10° and +60°. Since dilute emulsions follow the gas laws it is probable that concentrated emulsions would behave like compressed fluids, and that van der Waals' theory could be applied in studying them.: To determine the osmotic compressibility of the emulsion (i.e., the variation of the osmotic pressure as a function of the concentration of the grains) it is necessary to observe the distribution in a vertical column of emulsion, all the grains of which have been counted. The osmotic pressure at each level, supporting all the grains above this level, is thus determined. (The emulsion is its own manometer). absolute temperature, V = volume of emulsion containing N grains. b= four times the volume of these grains. a = a constant corresponding to the cohesion. If this is the case the observation of a concentrated emulsion will give Avogadro's number. Experiment verifies this prediction; it is found, however, that the constant of cohesion is negative, and that the grains repel one another to an appreciable distance. This result permits of the experimental determination of the thickness of the double layer of electrification by contact, and throws light upon the properties of colloidal solutions. A knowledge of the compressibility also provides a verification of the theory of Smoluchowski on the spontaneous fluctuations of the density of a fluid in a given volume. The activity of the E2 Brownian movement is defined as the quotient where E2 is the mean square of the displacement in time t. An emulsion should diffuse like, a solution of visible molecules with a speed which is greater the greater the speed of the molecules composing it. By calculation it is found that the coefficient Dot diffusion is obtained by dividing the activity by 6, and since at any level as many mole E? t. t cules pass upward by diffusion as pass downward by gravitation the coefficient of diffusion depends upon the radius of the grains and the viscosity z. Thus Einstein's equation holds, viz. : 255 CHEMICAL REACTIONS AT VERY LOW I. THE CLEAN-UP OF OXYGEN IN A TUNGSTEN LAMP. By IRVING LANGMUIR. Electron Theory of Chemical Combination. We have seen that the impact between oxygen molecules and tungsten atoms cannot be the determining factor in the reaction of oxygen with hot tungsten. The fact that the velocity of the reaction is not affected by the temperature of the oxygen indicates that the oxygen molecules react primarily with particles of very much smaller mass than themselves, therefore presumably with free negative electrons in the metal. Since the mass of the electrons is very small, their velocity must be very large in order that they may have the same average kinetic energy as the atoms of tungsten. From Equation (16) we see that when two particles collide the amounts of impact contributed by each are proportional to v1/M. If we consider the impact between oxygen molecules with an average temperature of 298° and negative electrons with velocities corresponding to 1600°, we find that the share of the impact contributed by the oxygen is to that contributed by the tungsten as √298/32 is to 1600/000055. That is, the movement of the oxygen molecule is only 1/560 as effective as that of the electron. This difference is so great that we can neglect the velocity of the oxygen entirely in its effect on the reaction. We have assumed that it is necessary for an electron and an oxygen molecule to collide with an impact exceeding a certain lower limit, in order that chemical combination may ultimately result. Since the velocity of the oxygen molecules is of so little importance, it is simply necessary, for chemical combination, that the electron shall strike the molecule with a velocity which exceeds a certain limit vo Let us now calculate what proportion of the electrons in a metal reach the surface with a velocity exceeding a certain value vo, and let us determine how this proportion increases as the temperature of the metal increases. This calculation is identical with that made by Richardson in determining the number of electrons that escape from incandescent metals (Phil. Trans., 1903, cci., 516). Let N be the number of electrons in each cc. of the Thus Avogadro's constant can be determined both by measuring the diffusion and by measuring the displacements. In order to study the diffusion emulsions were obtained which were such that the grains remained attached to the walls of the vessel when they came in contact with them. The emulsion thus became progressively weaker by diffusion, and the coefficient of diffusion was given by the increase of the number of grains captured as a function of the time. The displacements of spherules of known radius can be measured very easily, and these measurements, made in very varying conditions as regards the size of the grains and the nature of the intergranular liquid, all gave concordant results for Avogadro's number. Moreover, with relatively large spherules it is easy to measure the rotations, and thus verify Einstein's formula for the Brownian movement of rotation. All these theories apply to granules suspended in a gas, except that Stokes's law no longer holds good. By applying an electric field Townsend's where— equation for the diffusion of gaseous ions connects the charge on the granule with Avogadro's number and with the activity of its Brownian movement, viz. : metal. Then, according to Maxwell's law, the number dN = e-(v/a)2d(v/a). (19), Here is the square root of the mean square velocity of the electrons in the metal, and can be calculated by Equation (4) The number of electrons dn with velocities between v and vdu which reach a unit surface of the metal per second can be obtained by multiplying the number per cc. having this velocity by the velocity component perpendicular to the surface. That is, from (19)— Brownian movement of translation 62 69 65 бо 65 (62 65 |