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The entire profoundest interest, and an excellent pur ed by the publication of these papers in The Eagle (Brooklyn, N.Y.). "Sir William Crookes... has propounded a problem which in the next ce ntury [written in 1899] is bound to engage the close atte ntion not merely of agricultural experts, but of economists and statesmen."-Speaker. and considering the cheap issue ed in the feeding of the millions carefully."-Crieff Journal. chemists more seriously to what loomy prognostications result in interesting laboratory problem, have conferred an incalculable stern Morning News. the British Association erley. A CROOKES, RIAL and PHY. Special Articles on PICTO PROFUSELY ILLUSTRATED. Office: 51, LONG ACRE, LONDON, w.c. Simple Method for Determining Vapour-Densities. NEWS. CHEMICAL NEWS, July 9, 1909 THE CHEMICAL VOL C., No. 2589. A SIMPLE METHOD for deteRMINING VAPOUR- DENSITIES AND FOR ANALYSING BINARY MIXTU ES.* By PHILIP BLACKMAN. Apparatus. THE apparatus consists of a cylindrical vessel, closed at one end, and having at the other end a conical neck (the narrower end outwards) with a perfectly fitting, hollow, ground-glass stopper (see Fig. 1). The number repre 13 until it reaches a short distance from the rubberfixed end, and the rubber tube is then closed by means of a clip or pinchcock (see Fig. 2). The other exposed end is now sealed off in the blowpipe flame (see Fig. 3), the clip or pinchcock is removed, and the rubber tube taken off. 3. If the bore of the capillary-tube is not too narrow, one end is sealed off in the blowpipe flame. A refill (see Fig. 4) is made by softening in the flame one end of a piece of glass tubing and drawing it off to a long, fine capillary end. A little mercury is sucked up into it and kept within by placing the forefinger over the wide end; the narrow end is then inserted in the bore of the capillary tube, and when it has reached the desired position there, the hold of the finger is slightly eased, which will allow a thread of mercury to run into that part of the bore (see Fig. 5). senting the internal volume (cc.) of the bulb, when the stopper is fixed in the neck, is marked in permanent figures on the glass. (The apparatus is supplied by Messrs. F. E. Becker and Co., Ltd., 17-27, Hatton Wall, E.C.). Manometer, or Pressure-gauge. The manometer consists of a glass capillary-tube, somewhat shorter than the length of the body of the vessel, closed at one end and having a mercury-thread in the bore near the other end. It may be made by one of the three following methods, of which the second is perhaps the easiest as regards manipulation :: 1. One end of a piece of capillary-tubing, of the proper length, is sealed off in a flame. The tube is warmed in a flame, and the open end placed in some clean dry mercury; as the glass cools, the air within contracts and a thread of mercury is drawn in. 2. A piece of rubber tubing is fixed on to one end of the capillary-tube, and a thread of mercury sucked up through the other end; the mercury is drawn in Compare CHEMICAL NEWS, 1907, xcvi., 223; 1908, xcvii., 27, 102; 1909, xcix., 87, 133; Zeit. Phys Chem., 1908, Ixiii., 48, 381, 635; 1909, Ixv., 549, 745; Journ Phys. Chem., 1908, xii., 661; 1909, xiii., 138; Les Nouveautes Chimiques pour 1908, 15. Fig. 8. Method. 1. The manometer must be allowed to cool to room temperature, placed in a horizontal position, and the length, L, measured in mm., of the enclosed air-thread determined by means of a mm. scale or measure (see Fig. 6). 2. The substance to be experimented on is weighed out (weight = w) in a small stoppered glass weighing bottle. 3. A piece of thread or wire is wound round the handle of the stopper, which is then lowered into the vessel; the manometer and weighing bottle are placed within it, and the stopper is drawn into the neck and kept in place by winding the same thread or wire round the neck. Keeping the apparatus in a horizontal position, the length, L., in mm. of the manometric air-thread is again measured (see Fig. 7). 4. The external temperature, ti, and atmospheric pressure, p. in mm. are determined. 5. The vessel is heated in a horizontal position, in a suitable heating-jacket in the vapour of some substance boiling at a temperature above that at which the substance experimented on vaporises at ordinary atmospheric pressures, or better in a thermostatic trough containing some convenient heating medium such as glycerin or paraffin wax. THE DESULPHURISATION OF IRON.* When the substance has completely vaporised and THE FORMATION OF SILICON SULPHIDE IN the mercury index within the manometer has become stationary, the length, 1, in mm. of the manometric airthread is measured by means of callipers, compasses, or dividers, the distance between whose feet is then measured off along a mm. scale (see Fig. 8). 6. The vessel is removed, cooled, and opened by tapping the stopper; if the latter is tightly fixed the vessel must be further cooled by means of a little ether, which will have the effect of diminishing comparatively the internal pressure, and then, on tapping, the stopper will be forced inwards. (It is as well to wind loosely round the handle of the stopper and the neck a piece of thread to prevent the stopper flying inwards with violence and consequent risk of damage to the apparatus). The manometer and weighing bottle (opened) are removed and dropped into a burette nearly filled with water; the increase in volume due to their introduction will give the combined volume of the manometer and weighing bottle; the difference in value between this volume and that marked on the body of the vessel represents V, cc., the volume occupied by both the heated air and the vaporised substance. N.B.-a. The need of the thread or wire round the stopper and neck has already been explained. Otherwise the heated gases within exert sufficient pressure to keep the stopper in position, the greater the internal pressure the closer the fit. b. Before using the apparatus it must be well cleaned and thoroughly dried, and a current of air drawn or blown through it to remove any vapours. c. It will be found that with this apparatus L and Lc are generally equal in value. d. The temperature to which the vessel is heated is not required to be known unless for special purposes, such as, for instance, for the calculation of internal pressures (see the end of the paper). This formula may also be employed in determining the extent to which a substance, easily decomposed into two components when brought into the gaseous condition on heating, dissociates into its binary constituents. The apparatus inay also be employed to determine the amount, q, of a volatile component, of vapour-density, d, assumed known, given off on heating a compound to varying temperatures (e.g., to measure the quantity of water-vapour evolved from CuSO4.5H2O), the necessary calculation being carried out by aid of the formuladp LV (Lc 1) 31068 Lc (273+1) Internal Pressures. By W. FIELDING, B.Sc. THE object of the work was to investigate the conditions under which ferrosilicon can react with ferrous sulphide and liberate a sulphide of silicon. In the refining of steel in the electric furnace a very complete desulphurisation of the metal can be effected. This action is, in practice, found to be considerably facilitated by the addition of a charge of ferrosilicon. Several explanations have been put forward to account for this influence on the removal of sulphur. Some have ascribed it to the high temperature produced during the reduction of the ferrous oxide present by the ferrosilicon. Prof. Osann (Stahl und Eisen, July 15, 1908) believes that this removal of the iron oxide prevents the back action between it and calcium sulphide; at the same time a higher temperature is produced by the deoxidation, which assists the removal of sulphur as calcium sulphide. At the end of his paper he suggests the possibility of the formation of a gaseous compound, silicon sulphide. Max Haff (Electrochem. and Metall. Ind., March, 1908, p. 96) had previously declared that silicon sulphide was produced by heating together sulphides and silicides at a high temperature, but no details were given of his experiments. Silicon sulphide (SiS2) is described (Hempel and v. Haasy) as a solid at ordinary temperatures, which at a red heat sublimes under 60 mm. pressure. In the present work the reaction between ferrosilicon and ferrous sulphide was investigated by heating intimate mixtures of these compounds in a vacuum at known temperatures. The reacting substances were placed in a crucible in the form of a hollow graphite rod, which could be evenly heated by the passage of an electric current. Electrical connection was made with the rod by fitting it in graphite plugs, which in turn were soldered into watercooled brass tubes to which cables could be attached (compare Pring and Hutton, Trans. Chem. Soc., 1906, lxxxix., 1593; and H. C. Greenwood, Trans. Chem. Soc., 1908, xciii., 1485). The rod was surrounded by a water-jacketed Jena glass tube, for experiments in which the rod was heated below 1500°; above this temperature a silica tube was employed. The apparatus was made air-tight by luting the ends of the tube with soft wax. Temperature readings were made by means of the Wanner optical pyrometer in those cases in which a glass tube was employed, and changes in pressures were indicated by a mercury gauge connected with the tube (see Fig.). In experiments in which the commercial variety of iron sulphide was used the mass fused at a temperature of about 930° C., and a vigorous reaction set in with rise of temperature. In later experiments, using pure iron sulphide (free from oxide), no reaction was observed to about 1300° C., hence the reaction noted in the first case was probably due to reduction of oxide of iron present in the iron sulphide by the ferrosilicon. This explains the sudden rise of temperature noted. In all the experiments a yellow sublimate began to appear on the walls of the tube at a temperature of 1500° C. On removing this product and treating with water a rapid effervescence took place, sulphuretted hydrogen being liberated and silica separating. A larger quantity of this product was prepared by placing a mixture (40 grms.) of ferrosilicon and ferrous sulphide in a long graphite tube, which was closed at one end and fitted at the other into a porcelain tube to serve as condenser. The graphite tube was then placed in a horizontal carbon and the temperature was raised in stages. No sublimate tube furnace with the porcelain tube projecting outside, was formed until a temperature of 1700° C. was reached (the higher temperature required in this case being probably due to the experiment being carried out at atmos * Read before the Faraday Society, June 15, 1909. CHEMICAL NEWS, } Volumetric Estimation of Potassium in Animal Fluids. 15 IN ANIMAL FLUIDS. By W. A. Drushel. pheric pressure instead of at reduced pressure as before), | THE VOLUMETRIC ESTIMATION OF POTASSIUM when a yellow vapour was evolved, which condensed partly in the tube, the remainder being carried along by the stream of carbon monoxide gas coming off, which on being burned at the end of the tube smelled strongly of sulphur dioxide. About 4 grms. of the product were obtaired, which on analysis was found to consist of approximately 50 per cent silicon sulphide (assuming the formula to be SiS2), the remainder being iron sulphide which had volatilised, silica (obtained from the action of moisture in the air on the silicon sulphide), and a small amount of ferric oxide in a finely divided state. In different experiments products of variable composition were obtained. The silicon sulphide was estimated by acting on it with water in a Schrotter's apparatus (fitted with a calcium chloride drying tube) and determining the weight of sulphuretted hydrogen evolved. The gas evolved, after being efficiently dried by calcium chloride, was passed into weighed potash bulbs, and the increase in weight of the potash bulbs was found to correspond to the loss in weight of the Schrotter's apparatus. The weight of silicon sulphide (SiS2) corresponding to this weight of sulphuretted hydrogen was then calculated. The product remaining THE distribution of potassium in plant and animal tissues has been studied by Macallum (Journ. of Physiol., xxxii., 95) and others. Macallum precipitated potassium in place as potassium sodium cobalti-nitrite, an insoluble potassium salt which by its crystalline form and colour is easily recognisable under the microscope. To study the function of potassium in the animal organism it is desirable to have a simple and rapid method for its estimation in the various tissues and fluids. A number of quantitative methods have been proposed which, however, are not wholly free from objections. M. Kretschy in 1876, after having carefully studied the several indirect methods for potassium and sodium in the presence of each other, finally adopted a modification of the chlorplatinate method for potassium in the presence of relatively large amounts of sodium in physiological work. He worked with quantities of potassium ranging from 3 mgrms. to 120 mgrms., precipitating it as the chlor ୮ in the apparatus was then treated with dilute sulphuric | acid, and the gas evolved driven over into weighed potash bulbs, and the corresponding amount of ferrous sulphide calculated. The estimation of the ferrous sulphide was further confirmed by determining the amount of iron present in the solution, which was found to correspond to the amount of iron sulphide present. It will be observed that it has not been possible to fix the identity of the sulphide of silicon present in the product. An attempt was made to prepare the silicon sulphide in greater purity by distilling the product in vacuo, but up to 1100° C. no volatilisation was observed. No attempt was made at higher temperature, as iron sulphide is also volatile above 1100°. According to Hempel and v. Haasy silicon sulphide (SiS2) distils at red heat under 60 mm. pressure; this tends towards the conclusion that it is a much less volatile sulphide of silicon which is here produced. Rubidium Peroxide Hydrate and Rubidium Percarbonate. Erich Peltner. The action of hydrogen peroxide solution on solutions of rubidium hydroxide in absolute alcohol gives a strongly hygroscopic and unstable compound, the analysis of which presents many difficulties. If, however, it is protected from the action of damp air a rapid analysis can be performed. The results of such experiments showed that its composition is expressed by the formula RbOOH + H2O2. The substance when first prepared is white, but it rapidly turns yellow, and apparently the compound RbOOH + H2O2 is transformed into the higher oxide Rb204 with loss of water. Percarbonates of rubidium, Rb2CO4+2H2O2 + H2O, Rb2CO4 + H2O2 + 2H2O and Rb2CO4+2H2O, can be prepared by leading CO2 into the peroxide hydrate. These are very hygroscopic substances which readily lose active oxygen. This research shows that rubidium, unlike sodium and potassium, is capable of yielding higher compounds with H2O2. This was to be expected, for the peroxide of rubidium, Rb204, contains considerably more active oxygen than the peroxide of sodium Na2O2.-Berichte, xlii., No. 8. T platinate in the usual manner. The washed and dried precipitate was carefully ignited, the residue extracted with water, and the extract evaporated to dryness. This residue was gently ignited and weighed as potassium chloride. A small amount of platinum usually passed through the filter, giving a result which was too high for potassium chloride. To avoid error on this account the weighed potassium chloride was dissolved in water, any residue of platinum filtered off on ashless paper, ignited, and weighed, and the necessary correction made in the weight of the potassum chloride. Some years later Lehmann (Zeit. Physiol. Chem., viii., 508), Bunge (Zeit. Biologie, ix., 139), Heintz (Pogg. Ann., Ixvi., 133), and Pribram and Gregor (Zeit. Anal. Chem., xxxviii., 409) used different modifications of the Fresenius chlorplatinate method for the estimation of potassium in urine. In the methods of Lehmann, Bunge, and Pribram and Gregor the sulphate radical was removed by an excess of barium hydroxide or barium chloride; subsequently the excess of barium was removed by ammonium carbonate and ammonium hydroxide, or in case of barium hydroxide by carbon dioxide. Lehmann evaporated the urine with ammonium sulphate before ashing the residue, while Bunge treated the urine directly with barium hydroxide. Pribram and Gregor oxidised the organic matter by heating the urine, acidified with sulphuric acid, to the boiling-point and adding an excess of potassium free barium permanganate. Heintz treated 20 cc. to 30 cc. of clear urine with chlorplatinic acid and a threefold volume of a 1:4 ether and absolute alcohol mixture. After standing twentyfour hours the precipitate was filtered off, washed with alcohol, dried, ignited, and weighed. The residue was then extracted with hot water, and again dried and weighed. The amount of potassium chloride was found by taking the difference of the weights. It has been repeatedly shown that appreciable amounts of the alkali salts are carried down by barium sulphate, which cannot be completely removed by washing. This objection applies to all of the methods in which the sulphate radical is removed by means of a barium salt. The loss of alkalis is especially appreciable where a large amount of barium |