196 BEKRY: THE ADSORPTIOX OFXXL- The Adsorption o f Ui-uniurn-X by BariumBy ARTHUR JOHN BERGY, B.A.BECQUEREL has shown (Conzpt. rend., 1900, 131, 137; 1901, 133,977) that when barium is precipitated as sulphate in a uraniumsolution, the photographic activity of the latter is removed by thebarium sulphate. A similar result was obtained by Sir WilliamCrookes (Proc. Roy. SOC., 1900, 66, 409), who found that uraniumcompounds could be obtained photographically inactive by a singlechemical operation, the whole of the photographic activity beingconcentrated in a small residue termed uranium-X by Crookes.Soddy (Trans., 1902, 81, 860) showed that the whole of the &rayXulphateURANIUM-X BY BARIUM SULPHATE. 197activity of uraniam is due to the uranium-9, which is one of thedisintegration products of uranium (Rutherford and Soddy,Phd. Mag., 1903, [vi], 5, 441).I n the present communication, the adsorption of uranium-X hasbeen investigated quantitatively, and evidence has been obtainedof a, definite “ partition coefficient ” between the uranium-X in thebarium sulphate and in the solution.As the experiments wereapproaching completion, the author’s attention was directed to apaper by Ritzel (Zeitsch. physikal. Chern., 1909, 67, 724). Ritzelinvestigated the absorption of uranium-X by carbon, and hementions (Zoc. cit., p. 727): “Als Adsorbens wollte ich zunachstBariumsulphat verwenden Vorversuche zeigten aber bald dass dasBariumsulphat, von Versuch zu Versuch, mit sehr schwankenderKristallgrosse ausfallt, und man kann deshalb keine guten Resultateerhalten.” The present writer did not experience any difficulty ofthat kind.It was usually found perfectly easy to repeat a resultunder any given conditions. However, the use of barium sulphateis a disadvantage in studying the effect of time in the adsorptionof uranium-X, as it is probable that the crystals would increase insize with lapse of time.EXPERIMENTAL.A solution of pure uranyl nitrate (Merck), containing 400 gramsper litre, was employed. This solution was in radioactive equi-librium. Experiments were always carried out with 25 C.C. of thissolution. The B-ray activity due to the uranium-X in this quantityof material was determined by Crookes’s original method (Zoc. cit.).The liquid was diluted considerably, heated to boiling, a trace offerric chloride added, and ammonium carbonate added in quantitysufficient t o redissolve the precipitate of uranium carbonate.Theliquid was then filtered from the ferric hydroxide, and the activityof the uranium-X, removed by the latter, measured by a &rayelectroscope.The caseof the instrument was a stout brass cylinder, the internal diameterbeing 10.1 cm., and the internal height 12.6 cm. The base of theelectroscope was of aluminium foil 0.1 mm. thick. The pre-parations were placed on a, board at a fixed distance (7.7 cm.)below the base of the instrument. The rate of leak was determinedin the usual way with a reading microscope and a stop-watch. I ncvery case, the “ natural leak ” of the instrument was determinedand allowed for.This natural leak varied but slightly, the usualvalue being 3.7 scale divisions per minute. The measurements werealways compared with the leak due to a standard consisting of blackThis electroscope was of the ordinary single-leaf type198 BERRY: THE ADSORPTION OFuranium oxide. The mean of three concordant determinations ofthe &ray activity in 10 grams of uranyl nitrate carried out in thismanner was 106.6 scale divisions per minute.It was always possible to separate more than 90 per cent. ofthe uranium-X in the first operation by Crookes's method. Onacidifying the filtrate with nitric acid, and repeating the process,practically all the remaining uranium-X was removed. This waschecked by testing the residue after ignition.Unless otherwise stated, the experiments were conducted asfollows.The measured quantity of uranyl nitrate solution wastaken, acidified with a given quantity of a 10 per cent. solution ofsulphuric acid, and a quantity of water added, which, togetherwith the quantity of standard barium nitrate (2.5 grams per litre)employed for precipitation, would make the solution up to somedefinite volume. The precipitation was carried out in the cold, andthe liquid kept overnight. The solution was then boiled for oneminute, the barium sulphate collected, and its &ray activitymeasured. The, absorption of the &radiation in the barium sul-phate may be neglected, since the greatest mass of precipitate onthe filter paper wi19 only 0.11 gram.If there is a definite equilibrium between the uranium-X in thebarium sulphate and in the liquid, we should have:where C is the concentration of the uranium-X, and k and n areconstants.The concentration in the barium sulphate is x / m ,where x is the amount of uranium-X adsorbed, and m the mass ofbarium sulphate. The concentration in the liquid is a - 5/21, wherea is the initial quantity of uranium-X and v is the volume of thesolution. If there is equilibrium we should have:Series I.--a = 106.6 divisions per minute.sulphuric acid added to liquid. v=150 C.C.m(gram).0.00440.00880'01100.01540.0330 0440.0660-088X(divisions perminute).2 75-36 *38.114 -719 -321.824 *11 C.C.of 10 per cent.0 '740'720'7209'30.740 '740.770 -7URANIUM-X BY BARIUM SULPHBTE. 199Series ZZ.-a=106*6 divisions per minute. 10 C.C. of 10 percent. sulphurk acid added to liquid. .v=250 C.C.?n(gram).0'00440'01100'0220.0330'0440.0550.0880'110x(divisions perminute).4 *115.138'747-754.760.370-376.9I_sg(a-X) 1 -_log ?- -nm0.680-630.570 5 60.560 *550-540'52Series Z2I.-In this series the procedure was somewhat different.The uranium-X from one quantity (25 c.c.) of uranyl nitrate wasremoved by successive precipitations on separate days. The filtrateswere always made up to a constant volume (140 c.c.), and pre-cipitated each day by 10 C.C. of the solution of barium nitrate;15 C.C.of 10 per cent. sulphuric acid were added a t the beginningof the series only. In calculating l/n, a correction wasmade for the value of (a- x), owing to the solution recovering itsuranium-X content with time. The correction wm made by itrecovery curve for uranium-X. a (initially) =106.6 divisions per minute.(a - x)v = 150 c;c.m = 0.022 gram.X log (a - x) (corrected)-- - . (divisions per (corrected for log 2. 5% minute). recovery of Ur.-X). m43'7 64-6 0 -5530 '4 35 -8 0 -5017-3 21.0 0 *4610'0 13.7 0 -435.6 11 *o 0 *43Series Z V.--This series is precisely similar to series 111, exceptingthat 20 C.C. of 10 per cent. sulphuric acid were added to start with.v = 150 c.c., m = 0.022 gram, and a (initially) = 106.6 divisions perminute.2 log (a - 2 ) (corrected) -- (a - z)- m (divisions per (corrected for log x .nminute).recovery of Ur. - X ) . m45-0 63 ' 0 0 -5430 '4 34.7 0'4917.0 20 *1 0.458.7 13.9 0 *445 *6 11'2 0 -44From series I and 11, it is evident that dilution and excess ofsulphuric acid favour the adsorption of uranium-X, other thingsbeing equal. The influence of these two factors, separately, wasconfirmed by numerous other experiments, which it is unnecessaryto describe hereZOO TlTHERLEY 2-PHENYL-1 : 3-BEEZOXAZINE-4-ONE.Series I11 and IV are of interest, inasmuch as continuallydiminishing the concentration of the uranium-X in the solutionscarcely affects the constancy of 1 /!a.With regard to the effect of time, the following experimentalfacts may be of interest.It was found that as much uranium-X wasadsorbed by the barium sulphate two hours after precipitation aswhen the liquid was kept all night after precipitation. But if theliquid was kept for three days before collecting t.he barium sulphate,the quantity of uranium-X adsorbed was greater. This wouldappear to indicate that adsorption takes place very rapidly atfirst, but that diffusion of the uranium-X into the barium sulphateparticles takes place afterwards, and this latter process goes onfor a considerable time. However, no great importance is to beattached to these time experiments, owing to the probable increasein size of the adsorbing particles. For the same reas~n, it isdifficult to obtain evidence as to whether there is a definiteequilibrium between the uranium-X in the solid and liquid phaseswhich can be approached from both sides. Such a reversibleequilibrium has been shown t o exist in the case of the partitionof uranium-X between carbon and solution by Ritzel (Zoc. cit.,p. 735); who finds that for this equilibrium the equationCl = constant x C k , where CJ and Ck denote the concentration of theuranium-X in the solution and in the carbon respectively.The author desires to express his sincere thanks to Mr. Soddy forthe interest he has taken in these experiments and for his valuablesuggestions.PHYSICAL CHEMISTRY LABORATORY,GLASGOW UNIVERSITY