Jan. 13, 1911

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THE WHEAT PROBLEM:

Based on Remarks made in the Presidential Address to the British Association at Bristol in 1898.

REVISED WITH AN ANSWER TO VARIOUS CRITICS

By SIR WILLIAM CROOKES, F.R.S.
SECOND EDITION.

VITH PREFACE AND ADDITIONAL CHAPTER, BRINGING THE
STATISTICAL INFORMATION UP TO DATE.

With Two Chapters on the Future Wheat Supply of the United States, by MR. C. WOOD DAVIS, of Peotone, Kansas, and the HON. JOHN HYDE, Chief Statistician to the Department of Agriculture, Washington. "Sir William discusses at length the criticisms passed upon his address, and he appends valuable papers supporting his arguments on the future wheat supply of the United States."-Globe.

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CHEMICAL NEWS, Jan. 13, 1911

JA

VOL. CIII., No. 2668.

MESOTHORIUM.

By W. MARCKWALD.

IN 1907 O. Hahn (Berichte, xl., 1907, 1462, 3304) indirectly proved that thorium, on undergoing radio-active atomic disintegration, was converted into a metabolon, of which the half-constant was about five and a-half years, and which was separated from thorium during the working-up process of the preparation of the element from its ores. He called it Mesothorium. Subsequently Hahn detected this substance in the residues. He showed (Zeit. Phys. Chem., ix., 1908, 246) that mesothorium is not directly converted into radio-thorium, but that a short-lived intermediate product, mesothorium II., results (half duration of life 6 2 hours). Recently Hahn (Lecture at the Meeting of the German Chemical Society, July 11, 1910) succeeded in concentrating the substance to such an extent that its action considerably exceeded that of an equal weight of pure radium salt. The author has not published any details of the chemical properties of mesothorium I., and the method of discovering and preparing it.

A short time ago I received from a chemical works a "radium preparation" which I was to investigate, determining its percentage of radium. It consisted essentially of barium chloride. Judging from its y-radiation it must have contained more than I per cent of radium chloride. But when its power of emanation was investigated it was found that the radiuin emanation evolved corresponded to only about o'2 per cent of radium. Further investigation showed that the greater part of the y-radiation (about 80 per cent) was due to mesothorium II. For if a trace of ron chloride was added to the aqueous solution of the salt and it was then made ammoniacal, the mesothorium II. was precipitated with the iron hydroxide. A strong y-radiation was emitted by the precipitate, while the barium chloride obtained by evaporating the solution had lost almost the whole of its power of emitting y-rays. But while the precipitate lost almost all its power of radiation with a half-constant of about six hours, the salt regained the greater part of its power of radiation in a day. The ammoniacal precipitate must thus contain the radiothorium formed from the mesothorium. As a matter of fact, after the decay of the mesothorium II. there remained a residue which emitted a-rays, and which gave thorium emanation.

In reply to my enquiries the factory informed me that their "radium preparation" had been obtained by working up residues from ores containing uranium and thorium.

Evidently mesothorium is completely analogous to radium from a chemical point of view. I have not yet succeeded in finding a reaction by which it can be separated from barium and radium. On re-crystallisation of the chloride it accumulates with the radium in the difficultly soluble crystallisations.

This complete similarity of the two radio-active elements is very interesting. For up to the present no method has been found of separating by chemical reactions the four elements-thorium, radiothorium, ionium, and uranium X. Now it seems as if another group of radio-active elements of similar properties exists; to this group belong radium and mesothorium, and possibly other metabolons.

The study of the chemical properties of mesothorium reveals a method of preparing it from the residues of the manufacture of thorium. It is an exact reproduction of that by which radium is obtained from uranium ore residues. Of course the mesothorium preparations obtained from monazite must contain radium, owing to the presence of uranium in them, since no method of separating these two substances is known. Moreover, the radium obtained

As the duration of life of radium is about 300 times that of mesothorium it is very important when studying a "radium preparation" to take into account the possibility of its containing mesothorium. As in the case I have mentioned a useless preparation was sold with the best intentions, there is also the danger of deliberate adulteration. The simplest way to test a radium preparation for mesothorium is to heat it for a short time to drive off the emanation. The preparation must then lose its y-radiating power after a few hours, completely regaining it only after the lapse of many weeks. Instead of heating it, it can of course be dissolved in water and the solution evaporated. If after the radium emanation has been driven off, and the radium C has been destroyed (which takes a few hours) there is still some y-radiation, this is due to mesothorium. The ratio of the y-radiation before and after the treatment is a measure of the proportion of radium and mesothorium in the mixture.-Berichte, xliii., 3420.

THE ESTIMATION OF FREE AMMONIA AND AMMONIUM CARBONATE BY TITRATION. By J. C. THOMLINSON, B.Sc.

IN estimating free ammonia and ammonium carbonate in solutions containing an excess of the former a quick volumetric method may be used.

Free ammonia cannot be titrated using phenolphthalein as an indicator, methyl-orange being usually used; however, when it exists in the free state, and as carbonate, by using phenolphthalein first, and titrating until the liquid assumes a transient pink coloration throughout its entire bulk, we can obtain a close approximation as to the amount of ammonium carbonate present, and by then adding methyl-orange and completing the titration estimate the total ammonia.

To prove this a solution was made containing o'78 grm. free ammonia, NH3, per 100 cc., and 3.69 grms. ammonium carbonate, (NH4)2CO3, per 100 cc.

To 10 cc. of this solution phenolphthalein was added, and when titrated with normal sulphuric acid as the mean of two experiments, 8.1 cc. N. H2SO4 were required.

Calculated as ammonium carbonate, (NH4)2CO3, this represents 3:42 grms. (NH4)2CO3 per 100 cc.

The total ammonia free and existing as carbonate in the test solution made above would be, by calculation, 2.16 grms. per 100 cc.

A further titration after adding methyl-orange to 10 cc. of the liquid already titrated for carbonate gave the total amount of normal sulphuric acid solution required as 125 cc., representing 21 grms. total ammonia, NH3, per 100 CC.

Methyl-orange commonly used as an indicator for the titration of free ammonia, although not feasible as an indicator in the presence of free carbon dioxide, can hence

be used when there is an excess of ammonia in ammonium

carbon solutions, and the reliability of the titration for carbonate for quick and approximate analysis may be judged from the figures given above.

Royal Institution. On Tuesday next, January 17, at 3 o'clock, Prof. F. W. Mott begins a course of six lectures at the Royal Institution on "Heredity." On Thursday, January 19, at the same hour, the Astronomer Royal, Mr. F. W. Dyson, delivers the first of three lectures on "Recent Progress in Astronomy"; and on Saturday, January 21, also at 3 o'clock, Mr. Arthur Hassall commences a course of three lectures on "Problems in the Career of the Great Napoleon." The Friday Evening Discourse on January 20 will be delivered by Prof. Sir James Dewar on "Chemical and Physical Change at Low Temperatures"; on January 27, by Prof. William H. Bragg, on "Radio-activity as a Kinetic Theory of a Fourth State of Matter"; and on February 3, by Arthur E. Shipley, on "Grouse Disease."

1. The Apparatus. By H. J. S. SAND. IN previous publications apparatus for the rapid electroanalytical determination and separation of metals has been described, the principal advantages of which have been set forth in detail (a, Trans. Chem. Soc., 1907, xci., 373; b, Trans. Chem. Soc., 1908, xciii., 1572; c, Trans. Faraday Soc., 1909, v., 159). Attention is here only drawn to the ready adaptability of the apparatus to varying quantities of electrolyte, and to the fact that the efficiency of stirring is independent of the strength of

by making the anode wherever possible of glass, and the An anode made largely of glass has already been described on a former occasion (loc. cit. a), but the use of this has been discarded owing to the fact that it was too fragile.

Figs. 1a and 1b show the apparatus as now employed. The inner electrode a* is designed to be gripped at the top by the clutch described (loc. cit. b), its wide glass stem rotates inside the glass tube A, which latter is gripped by the collar P of the outer electrode, and held by the clamp of one of the stands previously described. In this electrode platinum is only employed in the gauze cylinder B, in the strips of gauze c which lead into the interior of the electrode to the copper wire D, and in the strips E leading out at the top, which are wound over by the platinum wire F. This latter forms a ring against which contact is made by the blocks of the clutch previously referred to.

Attention may be drawn to the following points :-All connections through the glass are made in the manner previously repeatedly referred to, by strips of platinum In the present case these strips are taken in threefold thickness at the top, and have a width of not less than I cm. below, so that it is possible to pass currents up to 10 ampères through the electrode without endangering it.

gauze.

2

H

3

4

A

-5

6

7

8

9

_10

FIGS. 14 AND 1b.

current employed. These advantages are absent from all those methods of working in which the current itself is utilised to stir the liquid, and which might otherwise appear attractive from the circumstance that they do away with the expense of a motor.

It was felt, however, that the amount of platinum employed essentially made the apparatus somewhat expensive, and the present communication contains a description of electrodes which may be used in a very considerable number of cases, and which, while retaining as much as possible the features of the former apparatus, only require a minimum amount of platinum. This has been achieved

• A Paper read before the Faraday Society, December 13, 1910,

FIG. 2.

The gauze cylinder B is fitted to the bottom of the electrode by blowing the glass against it. At the top, the cylinder stands off from the glass by 2 or 3 mm. in order to allow the gas bubbles which are thrown inwards in consequence of the action of centrifugal force on the liquid, to escape readily. It is held securely by four small protuberances g on the glass. The copper wire is held in the interior of the tube H by the enamel support i. The platinum wire F is wound in such a manner as to allow its ends to be twisted together at the bottom so that there is no risk of its being pulled off. The stem is widened at K just enough to prevent the tube A from being pulled off, but not enough to hinder the collar P of the outer electrode from being slipped over it. The contraction of the stem at L serves for the purpose of allowing the space between the latter

The inner electrode was made to my instructions by Universitätsmechaniker a. D. Fritz Köhler, of Leipzig.

CHEMICAL NEWS,

Jan. 13, 1911

and the guide-tube A to be washed down readily with a few drops of water before disconnecting. The total weight of platinum in this electrode is about 5 grms.

For copper determinations a cathode of silver was used; for zinc determinations one of nickel was employed. In the former case the electrolytic deposit was readily removed at the end of an experiment by means of a hot dilute sulphuric acid solution (1:10) to which some hydrogen peroxide (2 cc. perhydrol per 100 cc.) had been added. The same stripping solution was used a very considerable number of times. The use of a nickel cathode for zinc determinations is not novel, and needs no further comment. The cathodes do not differ very essentially from those previously described, but great attention has been paid to design them in such a manner that they may be constructed without much trouble with the appliances usually available in a chemical laboratory. The electrode is made only of two principal pieces, viz., (1) the frame, which is cut from a single piece of metal sheet of about half a mm. thickness, and bent into the shape shown, and (2) the gauze. From the latter a cylinder is first constructed, and the final form is obtained by introducing eight small pleats at the top, the size of which can be easily calculated beforehand. These pleats also serve to hold the frame in its place at the top of the gauze, whereas it is fastened below by means of four stout rivets. For the silver cathode fairly coarse gauze (Kahlbaum's coarse gauze) was employed. Owing to the softness and brittleness of the metal it was found desirable to leave no loose ends, but to finish off all the edges in the oxygen blowpipe. It was found easiest to do this by removing a few horizontal threads, and then melting down the projecting ends of the vertical wires. In a similar way the vertical joint in the gauze cylinder was made by removing a few of the vertical wires so that about 5 mm. of the horizontal threads protruded from each end. These latter were then twisted together, and the ends thus obtained were fused down and flattened, thus giving to the joint the appearance shown in the figure. In the case of the nickel cathodes fusing of the loose wires was obviously not feasible, but it was here unnecessary owing to the much stiffer nature of the material. The ends were simply pleated over, and joints made where necessary by fastening with either nickel rivets or wire. The mesh used was II per linear cm.

The electrodes may conveniently be formed on suitable glass dummies, which may also be employed to return them to their proper shape if they should accidentally be bent out of form. Copper electrodes may also be made by the identical process employed for those of silver.

The

With regard to the practical application of these electrodes the following remarks may be made. numbers given by Mr. Smalley prove that in copper determinations it is possible to obtain as good results with them as with platinum electrodes. There appears, however, to be an appreciable difference in favour of the platinum with regard to the slowness with which the copper goes into solution during the process of disconnecting. Rapid work is therefore desirable during this operation, and, if possible, a large current should be kept passing,

This experience is easy to explain when we remember how very much greater the polarisation capacity of platinum is than that of silver, in consequence of the greater solubility of hydrogen in the former. Harmful couples between the copper and the metal of the cathode will thus arise more quickly in the case of silver than in that of platinum.

A slight blackening at the top of the frame of the silver electrode generally takes place after electrolysis owing to the action of ozone, but apparently does not affect the results appreciably.

The zinc determinations caused no more difficulty with the nickel electrode than with that of platinum. The zinc was removed by warm dilute hydrochloric acid, and the electrode became slightly discoloured after some time without any effect on the results, The glass of the stem of the anode and of the guide-tube is ground down slightly

15

during use, and is found as a turbidity in the exhausted liquids, but no effect of this on the results was noticed. In conclusion, attention may be drawn to a stand illustrated in Fig. 2, which has been designed to take all the auxiliary apparatus required during analysis. It will be seen that there is a compartment at the back in which the circular block of wood used for raising the tripod is visible. In front of it there is a compartment for the thermometer, and in front of this a compartment for the split cover-glasses. The alcohol and ether jars are held in recesses, by means of a wooden bar, in such a manner that it is impossible to upset them. This bar is held by two round-headed screws (not visible), and has two vertical slits which allow it to be slipped into position or removed without undoing the screws. This base of the stand is extended in front to give it more stability, and the washbottle and spare beaker required in analysis may conveniently be placed on the extension.

Mention may also be made of the fact that Mr. Smalley has often found it convenient to replace the glass coverglasses by such cut from pieces of mica.

2.

Results obtained with the foregoing Apparatus in the
Analysis of Solutions containing Copper and Zinc.
The Determination of Zinc from Citric Acid Solutions.
By W. M. SMALLEY.

Copper. A standard solution of copper sulphate was made by dissolving a known weight of purest electrolytic copper (Kahlbaum) in nitric acid, evaporating down to dryness with a small excess of sulphuric acid, and diluting to 1 litre. Twenty-five cc. of the solution thus obtained were calculated to contain o'3025 grm. of copper, and the electro-analysis with platinum electrodes confirmed 0.3025 grm. Known quantities of this solution were taken for each determination.

To obtain good results warm solutions were always employed. The difficulty of washing the deposit without loss was minimised by having only very small quantities of nitric acid in the electrolyte. At the same time it was found better not to do away with this acid altogether, since, as is well known, it improves the density of the deposit very much. The general mode of working consisted in depositing the bulk of the copper with 10 ampères as long as the solution showed a blue colour, then removing the last traces with 5 ampères until the ferrocyanide or the hydrogen sulphide test showed the liquid to be free from copper, and then increasing the current to 10 ampères during the process of disconnecting. The beaker employed was a narrow form 200 cc. beaker, and the amount of electrolyte used was 110 to 120 CC. (Since these experiments were completed a smaller cathode has been made which may be employed in a 130 cc. beaker with 75 cc. of electrolyte, and which would thus allow the determinations to be completed a little more rapidly than those recorded). Table I. will show that the results obtained under these conditions with varying quantities of copper are practically as good as those usually got by means of platinum electrodes.

Zinc. -For the examination of the deposition of zinc a standard solution was made up by dissolving a known quantity of purest zinc (Kahlbaum) in nitric acid, evaporating off the latter with a small excess of sulphuric acid on the water-bath, and then making up to a known volume. The strength of the solution was checked by electro-analysis according to the acetate method with platinum electrodes, and found correct within the usual limits of error.

Table II. will show that equally accurate results are obtained with the present electrodes by the acetate method as with those of platinum.

The usual procedure was adopted. The solution was generally first made fairly acid with sulphuric acid to cause it to correspond with conditions actually met with in analysis, it was then made alkaline with caustic soda until the precipitate first formed had re-dissolved, and finally acid once more with acetic acid. During analysis a drop