CHEMICAL NEWS, Aug. 28, 1903. Intensely Penetrating Rays of Radium. ΙΟΙ For the methods of preparation of the gases I must refer to the former paper (Phil. Trans., A., 1901, vol. cxcvi., p. 508). The results were as follows; the rates of leak are given in scale divisions per hour, and are corrected to 30 inches pressure : Gas. each case, and were examined in a similar way. 4. Production of Helium by the Radium Emanation. The maximum amount of the emanation obtained from 50 m.grms. of radium bromide was conveyed by means of oxygen into a U-tube cooled in liquid air, and the latter was then extracted by the pump. It was then washed out with a little fresh oxygen, which was again pumped off. The vacuum tube sealed on to the U-tube, after removing the liquid air, showed no trace of helium. The spectrum was apparently a new one, probably that of the emanation, but this has not yet been completely examined, and we hope to publish further details shortly. After standing from the 17th to the 21st inst., the helium spectrum appeared, and the characteristic lines were observed identical in position with those of a helium tube thrown into the field of vision at the same time. On the 22nd, the yellow, the green, the two blues, and the violet, were seen, and in addition the three new lines also present in the helium obtained from radium. A confirmatory experiment gave identical results. We wish to express our indebtedness to the Research Fund of the Chemical Society for a part of the radium used in this investigation. Air Carbon dioxide Cyanogen.. to air as unity. The values of the same constants for the Gas. Hydrogen Oxygen Relative Ionisations. Carbon dioxide 1.53 1.86 Sulphur dioxide 2.19 4.88 31.9 4.80 72'0 5'31 ON THE INTENSELY PENETRATING RAYS OF RADIUM.* are 1. The a-rays, very easily absorbed by solids, and carrying a positive electric charge. 2. The B-rays, more penetrating than these, and negatively charged. 3. The y-rays, intensely penetrating, and not conveying an electric charge at all. In a paper published in the Phil. Trans. for 1901, I investigated the relative ionisations of gases by the a- and ẞrays. The present communication may be regarded as a sequel to that one, and deals with the y-rays. The radium employed was of activity 1000 (uranium = 1), and was contained in a glass cell, over which was cemented a piece of thin aluminium. The cell was placed in a cavity in a cavity in a block of lead, and over it was placed a disc of lead I c.m. in thickness. This it was considered would suffice to suppress all but the y-rays, which are much the most penetrating. In measuring the electrical leakage, the electroscope method was employed. The apparatus was that described in a paper published in the Philosophical Magazine for June, 1903, p. 681. The radium, covered by the thick lead, was placed under the apparatus, and the rate of leak determined when the different gases filled the testing vessel. The conditions were, of course, arranged so as to use a saturating E.M.F. The y-rays are so penetrating that there can be no question of their being appreciably absorbed in a moderate thickness of gas. * A Paper communicated to the Royal Society, August 5, 1903. 5'34 5.83 5.67 45'3 The determinations for the y-rays are less accurate than the former ones for the a- and B-rays, on account of the very much smaller rates of leak which have to be measured. I think, if this be taken into account, there is no reason to doubt that, within the limits of experimental error, the y-rays give the same values as the B-rays. These values are nearly proportional to the density of the gas, except in the case of hydrogen. The law which holds in the case of Röntgen rays is totally different. This conclusion throws some light on the nature of the y-rays. The view seems to be gaining ground that these are Röntgen rays, produced by the impact of the B-rays on the radium itself (see, for instance, Mdme. Curie, "Thèses presentées à la Faculté des Sciences," 1903, p. 83; Chem. NEWS, vol. lxxxviii., p. 85 et seq). This theory seems to have much to recommend it. The B rays should, by analogy with the cathode rays in a vacuum tube, produc Röntgen rays when they strike a solid obstacle, and these Röntgen rays should be much more penetrating than the B-rays themselves. The y-rays seem at first sight to be just what should be expected. But the present paper shows that, in one respect at all events, the y-rays behave quite differently to Röntgen rays, while, on the other hand, they resemble the a- and B-rays. There seems to be a possibility that they, too, are of a corpuscular nature, though uncharged with electricity. This would account for the absence of magnetic deflection. I do not think that the absence of conspicuous Röntgen radiation is very hard to understand, if we consider tha the current emitted in cathode rays by a square inch of intensely active radium is only 10-11 ampères; the current through a focus tube is of the order io-2 ampères, and probably a great part of this is carried by the cathode rays. ELECTROLYTIC APPARATUS.* By F. MOLLWO PERKIN, Ph.D. OWING to the great expense of platinum and the necessity for its use in electro-chemical analysis, members may be interested in the description of a simple form of electrode, which is comparatively inexpensive and is very satisfactory. In Fig. 1, which shows the electrodes, the cathode is in the form of a flag, and is made of platinum gauze, which is held rigid by means of a platino-iridium frame (10 per cent iridium); the frame, which is roughened by means of the sand-blast, has a stout piece of iridio-platinum wire welded on to it. The wire, of course, is for holding the electrode in position during analysis. The loop near the top of the wire is for hanging the electrode on the balance. The anode is made of iridio-platinum wire, and is bent upon itself in such a way that when it is placed into position for electrolysis, as illustrated in Fig. 2, an even current density is obtained on all parts of the cathode. The distance between the two sides of the anode is 2.5 c.m., therefore when in position it is 1.25 c.m. distant from each side of the cathode. The cathode is 6 c.m. high and 43 c.m. wide, and the length of the supporting wire is 7'5 c.m., the loop being 2.5 c.m. from the end. As the anode is opposed to both sides of the cathode during electrolysis, it follows from the above measurements that the total cathode surface is 50'4 c.m.", that is practically half a square decimetre, which, as the C.D. for analytical purposes is generally calculated per square decimetre of surface, is a very convenient size. It is not essential for the cathode to be made of gauze-in * A Paper read before the Faraday Society, June 30, 1903. FIG. 3. FIG. 2. Electrolytic Apparatus. 103 CHEMICAL NEWS, Aug. 28, 1903. centimetre. When it is too fine there is a tendency for hydrogen to collect upon the surface and thus cause polarisation. The weight of the cathode, when made of platinum sheet, is about 14'5 grms. If thinner platinum is employed the weight can be reduced to 8 grms., but I have found it better not to make them of very thin platinum, because then they are fragile, and there is a tendency for the deposits not to adhere well at the edges. The weight of the gauze electrode is about 15 grms. It follows that, as these electrodes weigh much less than the basin or cylinder ones, they are much cheaper. A basin usually weighs from 45 to 60 grms., and a cylinder from 26 to 28 grms. These electrodes are also more satisfactory for carrying out electrolytic separations, the manipulation being much easier than with the basin. Suppose, e.g., that one is electrolysing a mixture of copper and iron salts. In the first place the copper would be deposited out from an acid solution; then, after neutralising, the iron would be electrolysed out. Now when a basin is used, the solution has to be transferred to a beaker, and, as the manipulation has to be rapid, there is a danger of loss through spilling; further, the acid solution must not be left in contact with the copper deposit. The dish therefore must be washed at once, and the solution which is clinging to its sides, and which contains iron, is lost. In the case of the flag electrode, the cathode is rapidly raised out of the beaker and the solution at once washed off its sides, while it is hanging over the top of the beaker, by means of a wash-bottle. The solution in the beaker can then be neutralised without being transferred to another vessel; multiplication of manipulation is thus avoided. FIG. 5. FIG. 4. Apparatus for Rotating Electrodes. It is often necessary in electrolysis to keep the electrolyte agitated. This is generally done by means of an agitator, entirely separated from the electrodes and rotated by means of a water-turbine or motor. In many cases, however, much better results are obtained if one of the electrodes is itself caused to rotate. In most of the descriptions of rotating electrodes, there seems to have been considerable difficulty in obtaining good electrical contact, and the methods employed have often been rather complicated. Fig. 3 shows an arrangement which has been found to work extremely well. It consists of a supporting arm, made of gunmetal, the end of which is drilled to allow a spindle to pass. This spindle carries a small chuck (such as is used for fixing small drills on a lathe) which is used for fixing the rotator. The grooved pulley, which is fastened on to the upper end of the spindle, bears on the top of the arm, which is ground smooth. The whole arrangement is driven by means of a belt from a water-turbine or electrical motor. This arrangement is found to give very perfect contact and to work with very little friction. The parts should only be slightly lubricated, the best lubricant being a mixture of graphite and vaseline. The water-turbine, which has proved very useful and has been working for a long time, has ball bearings-an unusual nicety -and was obtained from Messrs. Baird and Tatlock, Glasgow. Fig. 4 shows another form of the rotator, which can be driven either from a horizontal or vertical pulley, and is also convenient for working several apparatus in series. The electrode shown in Fig. 3 is of iridio-platinum, and has been used with very satisfactory results in the electrical oxidation of organic substances. The electrode in Fig. 4 is of aluminium. I have found the following method work very well for making rotating lead electrodes. Thin lead pipe, to which the vanes for mixing the liquid are burned, is drawn over a steel rod of the same diameter as the bore of the pipe. The steel rod protrudes about an inch above the top of the pipe, in order that it may be fastened in the chuck. The pipe is burned at the bottom and the top to prevent the solution from running in between it and the steel core. If a central core such as this is not used, lead electrodes are not sufficiently rigid to use for rotating purposes. Rotating Cathode for Analysis. In Fig. 5 is shown a rotating cathode and a stationary anode for electrolytic depositions. It is found that the rate of deposition of a metal from its solutions is very much accelerated and that a higher C.D. can be employed when the cathode is kept in rapid motion. The cathode is a small cylinder of platinum gauze which has a combined surface of about 25 c.m.". The anode B is in the form of a double circle of stout platinum wire, and has four little baffles placed at intervals round it to prevent the liquid from rotating with the cathode. Of course, for peroxide deposits the rotating electrode would be the anode. A cylinder of sheet platinuni also gives very good results, but in this case very little metal is deposited upon the inner surface. Longitudinal slits, however, partially get over this difficulty, but with gauze as shown in the figure the deposition is practically equal inside and outside. To CHARLES PERRIN, ESQ., M.Inst.C.E., Water Examiner, Metropolis Water Act, 1871. London, August 10th, 1903. SIR,-We submit herewith, at the request of the Directors, the results of our analyses of the 218 samples of water collected by us during the past month, at the several places and on the several days indicated, from the mains of the London Water Companies taking their supply from the Thames and Lea. O 261 36 River Lea, unfiltered (mean of 27 samples) Of the 307 daily samples taken from the filter wells of Your obedient Servants, WILLIAM CROOKES. LIQUID BATHS FOR MELTING POINT By HEYWARD SCUDDER. A MIXTURE prepared by boiling together for five minutes seven parts by weight of sulphuric acid (sp. gr. 1·84) and three parts by weight of potassium sulphate remains a transparent liquid at ordinary temperatures, and can be In Table I. we have recorded the analyses in detail of heated up to 325° without boiling. If the proportions are samples, one taken daily, from July 1st to July 31st changed to six parts by weight of acid and four parts of the inclusive. The purity of the water, in respect to organic sulphate, the mixture forms a soft mass at ordinary temmatter, has been determined by the Oxygen and Com-peratures (though after boiling and then cooling down it bustion processes; and the results of our analyses by these methods are stated in columns XIV. to XVIII. We have recorded in Table II. the tint of the several samples of water as determined by the colour-meter described in previous reports. In Table III. we have recorded the oxygen required to oxidise the organic matter in all the samples submitted to analysis. Of the 218 samples examined by us during the month, 216 were found to be clear, bright, and well filtered; and two samples were recorded as slightly turbid. The rainfall at Oxford during July, though above the average, is considerably less than that recorded during June. The actual fall has been 3:47 inches; the average for the month is 2:49 inches; this gives an excess of o'98 inch, which, added to the previous one of 7.83 inches, makes a total excess for the year of 8.81 inches, which is 66 2 per cent above the thirty-five years' average. The results of the chemical examination of the London waters during the month of July show that the soluble In will usually remain liquid for half-an-hour or more) melting These mixtures are self-clearing, and remain permanently white (turning slightly yellowish at about 230°) unless much organic matter gets in. They can be cleared, if brown, by boiling with a few drops of concentrated nitric acid or with a small crystal of potassium nitrate. The vapour is so slightly acid that the capillary can always be fastened to the thermometer by a rubber band, provided the band is I to 2 c.m. above the surface of the bath. Platinum wire need never be used. In preparing the bath, after the potassium sulphate has melted the two layers should be mixed, or explosive boiling may occur. Most melting-points given accurately are below 325°. The first mixture is therefore suitable for all ordinary purposes. It does not have to be renewed frequently as does the ordinary sulphuric acid bath, nor does it become per. National Physical Laboratory. CHEMICAL NEWS, Aug. 28, 1903. manently discoloured as does paraffin after short use, even though prepared by distillation under diminished pressure. If the bath has solidified (which happens sometimes under unknown conditions, though very rarely), boiling for for a minute or two will bring it back to its original condition. If it has not been used for a number of weeks, it should be boiled for a minute or two before using for temperatures above 300°. For temperatures from 360° to 600° Mr. Booth, working under the direction of Dr. Mulliken of this laboratory, has found that the most satisfactory bath is fused zinc chloride. This melts to a clear transparent liquid at about 250°. After use it must be poured out on a tile while liquid, since it expands on solidification, and will crack any flask or beaker in which it is allowed to grow cold. It can be cleared from organic impurities by heating with a small crystal of potassium nitrate. Unless the zinc chloride used is pure, the bath will gradually become opaque after a short time, and cannot be made transparent again. Thermometry. 105 Dr. Harker has continued his comparison between the air thermometer, the platinum thermometer, and the thermojunctions, and the work is now complete for temperatures between o° C. and about 1050° C. The first part of the work for temperatures up to 500° C. was done with M. Chappuis, at Sèvres, and the results have been published. Dr. Harker is now preparing for publication results up to temperatures of 1050° C. obtained at Bushy. He has also constructed and subjected to stringent tests a set of platinum thermometers for the British Association. A small research on the specific heat of iron at high temperatures-700° C. to 1000° C.-is nearly complete and promises to be of interest. Electricity. Mr. F. E. Smith's research on the resistance of mercury and the construction of a standard mercury resistance is Some 10 or 12 tubes have been The value of The temperatures given here are uncorrected. were obtained in a melting-point apparatus made by inserting a test-tube in a round-bottom flask (150-250 c.c.). The bottom of the tube is about I c.m. from the bottom of the flask. The bath is placed both in the test-tube and in the flask. In this apparatus fresh sulphuric acid (sp. gr. 1.84) can be used up to 280-300°. In using the sulphate mixtures, if the upper part of the tube becomes cloudy from a film of solid, it can be cleared by boiling with a little concentrated nitric acid. In using such an apparatus it is not safe to heat it much above the temperatures given here for the Reichanstalt will not be more than some few parts in the various baths, since the boiling is apt to start very violently. It is safe to heat it till large bubbles begin to rise moderately frequently. practically complete. They calibrated, and give results which will only differ among themselves by some few parts in 100,000. the specific resistance of mercury will probably prove to be very close to that determined by myself and Mr. Fitzpatrick in 1888. On the assumption that the absolute value of the wire standards in the Laboratory is known, the length of the column of mercury, I sq. m.m. in section, having a resistance of 10o C.G.S. units is found to be almost exactly 106.29 c.m. When these baths are used in open beakers, it is not possible with sulphuric acid or the sulphate mixtures to obtain temperatures as high as those previously mentioned, without having disagreeable amounts of acid vapour given off. The zinc chloride bath can be used in a beaker up to about 600°. The sulphate mixtures seem to contain some compound in a persistent state of supersaturation. Although possessed of considerable oxidising power when hot, it is a curious fact that they are markedly less caustic than hot concentrated sulphuric acid when dropped on the skin. Journal of the American Chemical Society, xxv., No. 2. THE NATIONAL PHYSICAL LABORATORY. REPORT BY THE DIRECTOR ON THE WORK IN THE ENGINEERING AND PHYSICS DEPARTMENTS DURING the HALF YEAR Ended June 30, 1903. THE following statement was prepared by the Director, and laid before the Executive Committee at their Meeting on July 17th, as an interim report on the research work in progress. The Committee, believing it would be of interest to a wider circle, ordered it to be printed and circulated. Engineering Laboratory. In the wind pressure research the case of flat surfaces exposed to a perpendicular current of air has been fully worked out, and a general relation established which is now being tested for the case of larger surfaces exposed to the natural wind. The case of parallel plates at varying distances apart has been treated, and experiments are also Dr. in progress on the pressure on inclined surfaces. Stanton hopes to have a paper on the results obtained at present ready for publication very shortly. The Testing Machine for alternating stresses is nearing completion, and will, it is hoped, be ready for working in the Autumn. Drawings have been prepared and some preliminary tests made for the research into the constants of steam. The difference between Mr. Smith's results and those of 100,000. Mr. Smith has also made good progress with a research into some of the anomalies of the Clark Cell. An investigation of some importance into the changes in insulating strength of various dielectrics, used in motors, Campbell and Mr. Rayner, undertaken for the Engineering transformers, &c., due to continued heating, by Mr. A. Standards Committee, promises to lead to results of value. Metallurgy. In the Metallurgical Division preparations have been made for the work on Nickel Steel in conjunction with Mr. Hadfield; the material is being prepared by him. Meanwhile, considerable advance has been made with a series of determinations on some iron carbon alloys. The solidifying points and cooling curves of a series of pure iron carbon alloys have been determined, using platinum platinum-iridium and platinum platinum-rhodium thermojunctions. The range of carbon is from 0.15 to 3'55 per cent; the range of temperature from 1502° C. to IIII° C. on the thermojunction scale. About 15 alloys have been made, the weight of each being about 4 lbs. The ingots have been analysed for carbon, sulphur, and silicon. The percentages of the two last named elements do not increase during the time needed for melting. Further, the ingots are satisfactorily homogeneous in composition. The apparatus for taking cooling curves by the differential method is in working order, and the above mentioned alloys will be examined in this way. The Director hopes that a number of important results may be published during the Autumn. The equipment of the photometric room is approaching completion. The main photometer bench which is being standardised at the Reichanstalt has not yet been delivered. circular giving an account of the equipment and a stateOn its arrival the Director hopes to issue a special ment as to the conditions of the tests and the fees. REGULATIONS FOR THE EXAMINATION OF LISTER-GERBER |