and to G. E. Xartin‘s mechanical equipment development group. Tlw uranium standards were obtained from 11.H. Studier a t the Argonne National Laboratory. All samplrs were aliquoted a t this laboratory by A h . H. C. Hendrickson. Many of the analytical data were obtained by G. -4.Lumnianik and G. R. Hertel. Coiisultations with Alas Halperin aided statistical interpretation of the data.
No. 14, p. 24, (1954).
LITERATURE CITED
(1) Dietz, 1,. h.,Rtc. Sei. Inslr. 30, 235 (1959). (2jHali, L. I)., Ibid., 29, 367 (1958). (3) Hall, L. I)., Science 128, 279 (19 ttrium or rare earths prior to and during the cation exchange step would r a i v questions as to the interpretation of tliv function of the cation exchange resin These methods are evaluated below. I n attempts to apply the Carter and Dean procedure ( I ) to the dettvmination of the rare earths in inipii’e uranium oside. a sizable precipitate clvveloped in the fluoride solution, which n a s found to contain over 95% of the added yttrium carrier. An analysii identified the precipitate as mainly calcium fluoride with a minor amount of magnesium fluoride. T h r exact mechanism of the collection of the rare earth fluorides by a mixture of calcium and magnesium fluorides is not yet u n d w
stood, although it ha$ been noted (6j that precipitates of non-rare-earth fluorides may be rontaminated with rare earths m ithout ensuring complete precipitation of the latter. Subsequent tests with calcium and magnesium salts indicated that the collection of yttrium and rare earth fluorides in an environment containing large quantities of soluble beryllium, uranium, zirconium, or titanium fluoride is SO% or les, complete if calcium fluoride is the only precipitant. If magnesium is also present, recovery of yttrium and rare earths is virtually complete. It is assumed that the bulk of the yttrium and rare earths is coprecipitated with the calcium fluoride, with postprecipitation of magnesium fluoride ensuring an almost complete recovery. Prccipitation of the fluoride mixture is difficult in a medium containing large amounts of titanium fluoride, either TiF3 or TiF4,but becomes instantaneous if the solution also contains zirconium The function of the zirconium is currently under investigation. At first thought, the collection of a sizable calcium-magnesium fluoride pre(sipitate may appear unattractive. Fortunatcly, the subsequent removal of these salts is simple via cation exchange. The rnd product of the ion exchange separation is an eluate containing all the *yttrium carrier, added as a monitoring device, and also any rare earths originally present in, or intentionally added t o the sample. While the experiments reported here cover only the recovery of europium, dysprosium, gadolinium, and samarium, sufficient preliminary data have been collected to indicate that all the other rare earths and thorium can also be quantitatively collected by alcium-magnesium fluoride.
The proposed method covcrs the range above 0.1 p.p.ni. of each of the four rare earths, using a 50-gram sample. The range can be extended to lon cr concentrations by using an appropriately larger sample or less yttrium carrier. Ten grams of sample is sufficient to determine the four rare earths in concentrations above 1 p.p.m. when 5 mg. of yttrium is used as carrier.
Q
(
Table I.
Added, Sample (+rams Mg. Be0 50 10.0 30 50
25
:in _-
Be 30 Be(A1, Zr) 15 Zircalov-2 50
L-03
c
uoz
Apparatus. Xormal laboratory csquipment, including glass columns 15 X 1 inch (inside diameter) containing a settled resin bed of about 10 inches of 100- to 150-mrsh Dowex 50 or Amberlite IR-120 which has been washed first with 9.V and then with lLYhydrochloric acid. When analyzing zirconium-hase or titanium-base alloys, the columnP should contain the following from bottom to top: glass wool, followed by 3 inches of Dowcx 1 anion exchange resin (200mesh, S Y , cross linkage). glass wool, and 8 inches of Dowex 50 or Amberlite IR-120 cation exchange resin. Dissolution of Samples. BERYLLIUhl M E T a L A N D OXIDE:. Dissolve 10- t o 50-gram portions of t h e sample, suspended in 150 ml. of water in polyethylene beakers, by the gradual addition of concentrated hydrofluoric acid. A beryllium metal sample weighing 25 grams requires approximately 215 ml. of hydrofluoric acid, while 25 grams of the oxide is dissolved by about 80 ml. of the acid. Add sufficient concentrated hydrofluoric acid to raise the acidity to 2.5-W. TITANIUM hTETAL, ALLOYS,AND OXIDE. Dissolve 10 to 50 grams of the metal and 1 gram of pure zirconium, suspended in I50 ml. of water in a polyethylene beaker, by the gradual addition of a measured amount of hydrofluoric acid. After solution of the
Determination of EuZ03, Dyz03, G d z 0 3 , and Smz03in Beryllium, Uranium, Zirconium, and Titanium Metals, Alloys, and Oxides k'20,
Zr ZrO?
PROCEDURE
sample: aclcl tlroixvise sufficient nit1 ic acid to oxidize the titanium as indicated by the disappearance of the purple color. Add sufficient concrntrated hydrofluoric acid to raise thr acidit'y to 2.5.M. Hecause titanium oxide reacts only slowly with dilute 1iyd1,ofluoric acid, dissolve the former in the Concentrated acid, add a hydrofluoi,ic acid solution containing 1 gram of zirconium, and evaporate to near d i y ~ s s . Dilute with 2.5-11 hydrofluoric acid to 250 ml. Z I R C O S I U M l I E T A L , ALLOYS, .4ND OXIDE. Decompose the metal in dilute hydrofluoric acid as described for titanium and dissolve any tin (Zircaloy) or othei, precipitated metal by the dropwise addition of nitric acid. Dissolve zirconium oxide samples in concentrated hylrofluoric acid. I n either case, adjupt the hydrofluoric acid concentration to 2.5.11. URAXILX I\fET.
