ANALYTICAL CHEMISTRY
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Figure 4. Pyrohydrolysis of Chlorides in Presence and Absence of U308 the hydrolytic method to halides other than fluoride was of secondary interest. The easily hydrolyzed chlorides, such as cerium trichloride, uranium tetrachloride, and titanium trichloride XTere analyzed for chloride in the macroapparatus regulated a t 300’ to 700” C. The chlorides of alkali and alkaline earth chlorides. were mixed with uranium oxide (U308) as in the case of the corresponding fluorides, and hydrolyzed successfully (Table 111). Rate curves are given in Figure 4; they indicate that these chlorides react somewhat more rapidlv than the fluorides. In its present form, the pyrohydrolytic method must be con sidered unsatisfactory for chlorides, owing to the rather large (up to 1% j errors involved, but the results are sufficiently valid to suggest that further refinement would be fruitful. Little attention was given to bromides. Results were erratic, probably because of air oxidation or thermal decomposition of the hydrogen bromide formed. The method may possibly be adapted to bromides by using silica apparatus from which air is excluded and relatively low temperatures. PROCEDURE USING PYROHYDROLYTIC ACCELERATORS
Use of Uranium Oxide (U30J)as Pyrohydrolytic Accelerator. Pure uranium oxide ( U308) is prepared by strongly igniting uranyl nitrate in a platinum dish, first over a flame, and later in a muffle furnace a t 1000° C. The difficultly hydrolyzed fluoride or chloride is weighed into a small agate mortar containing a thin layer of the oxide and is then covered with a little more of the oxide. The total weight of uranium oxide (UIOs) is four to five times the weight of the fluorine (as F) expected, or two to three time? the weight of the chlorine (as C1) expected. ilfter grinding until homogeneous, the mixture is transferred to the platinum boat, and the last traces swept from the mortar by successive additions of small quantities of uranium oxide (U308). A small camel’s-hair brush proves helpful in the latter operations. The hydrolysis step is carried out as previously described. Use of Aluminum Oxide (A1203)as Pyrohydrolytic Accelerator. Reagent-grade aluminum oxide poJTder is substituted for uranium oxide in the above procedure. The hydrolysis time generally must be lengthened somewhat.
this ensured the compositions ThOn and U308. In 25 consecutive analyses of thorium fluoride using the macroapparatus, the average precision was 0.8 part per thousand for fluoride, and 0.5 part per thousand for thorium. Corresponding data for uranium(1V) fluoride were 0.6 and 0.5 part per thousand, respectively. Average results were 0.05% lower than theoretical in the case of fluoride in uranium(1V) fluoride. Average thorium and uranium results were 0.03’% lower than theoretical. Using the semimicroapparatus as described, analyses of thorium fluoride for fluoride suffered somewhat poorer precision-2.0 parts per thousand. Fluoride results from determinations involving the use of uranium oxide (U308) as pyrohydrolytic accelerator had a tendency to be low, probably because of insufficient grinding. Precision was correspondingly poorer. I t is estimated that fluoride and chloride results from alkali and alkaline earth halides averaged 0.4 to 0.8% lower than the true values, with a precision of approximately 5 parts per thousand. LITERATURE CITED
(1) Bergnian,A. G., et al., T r n n s . S t n t e I n s t . A p p l . Chem. (C.S.S.R.), No. 25,9-90 (1934). (2) Briner, E., Compt. rend.. 227, 661,703 (1948). (3) Briner, E., and Gagnaux, S . ,Hcli,. C h i m . A c t a , 31, 556 (1948). (4) Briner, E., and Roth, P.. I b i d . , 31, 1352 (1948). (5) Domange, L., Ann. chinz., 7, 225 (1937). (6) Domange, L., and Wohlliuter, M., Compt. rend., 228, 1593 (1949). ( i )Fremy, A . , Ann. chirn. ph?is., 47 [3], 17 (1856). (8) Iler. R . K . , and Tauch. E. ,J., T r a n s . Am. I n s t . Chem. Engrs., 37, 853 (1941). (9) Koch, C.W., Broido, -\., and Cunningham, B. B., J . . 4 n ~Chem. Soc., 74,2349 (1952). (10) Koch, C. W., and Cunningham, B. B . , I b i d . , 75, 796 (1953). (11) Lunge, G . , “Manufacture of Sulfuric Acid and Alkali,” 3rd ed., 5’01. 111,pp. 238 ff., New York, D . Van S o s t r a n d Co., 1909. (12) hlcKenna, F. E., .\-ucleonics, 8, S o . 6 , 24 (1951); 9, KO.1, 40; 9,X o . 2,’51(1951). rend., 52, 1267 (1861). hufarov, G. I., Zhur. Khim.P r o m . , 7,332 (1930). (15) Prideaux, E. B. R . , and Roper, E. C., J . Chem. Soc., 1926,898. (16) Rohinson, P. L., Smith, H . C.. a n d Briscoe, H. V. A , , Ibicl., 1926, 836. (17) Sheft. I., and Davidson, S . R.. Sational Nuclear Energy Series, D i r . IY, Vol, 14I3, Pt. I, pp. 831, 841, “ T h e Transuranium Elements,” New Tork, l\ZcGraw-Hill Book Co., 1949. (18) Solvay, E., Dinglers Polytech. J . , 225, 307 (1885). (19) Susano, C. D., Oak Ridge Sational Laboratories, Oak Ridge, Tenn., private communication. (20) Tammann, G., and Rosenthal, W., Z. anorg. u. allgem. Chcm., 156,20 (1926). (21) W n r f , J. C., Xational Suclear Energy Series, Div. V I I I , T‘ol. 1, p. 728 ff., “Analytical Chemistry of the M a n h a t t a n Project,” S e w York, McGram-Hill Book Co., 1950. (22) Warf, 6 . C., Cline, W.D., and Tevebaugh. R . D . , M a n h a t t a n Project, CC-1981 (Oct. 10, 1944); CC-1983 (Kov. 10, 1944); CC-2723 (June 30,1945). (23) Willard, H. H., and Winter.0. D., IXD.ENG.CHEM.,AXAL.ED., 5 , 7 (1933).
PRECISIOV 4ND ACCURACY
RECEIVED for review June 2. 1953. Accepted October 30, 1953. Presented before the Division of Analytical Chemistry at the 123rd Meeting of the SOCIETY,Los Angeles, Calif., March 1953. ContribuAMERICAN CHEMICAL tion 30.227 from the Institute for Atomic Research and Department of Chemistry, Iowa State College, Ames, Iowa. Work was performed under the Manhattan District of the U . S.Corps of Engineers.
Precision and accuracy for the analysis of fluorides by this method were determined n-ith fluorides which were prepared by hydrofluorination of pure oxides and which, upon pyrohydrolysis, furnished oxides that were suitable for gravimetric weighing. Thorium and uranium(1V j fluorides meet these specifications admirably. Many of the other fluorides studied contained considerable oxide, disclosing incomplete hydrofluorination during preparation. Thorium and uranium oxides and fluorides were available in spectrographically pure form, and the oxides resulting from hydrolysis were further ignited in the boats before weighing;
In the article on “Present Limitations of Platinum Group .Inalypis” [MacNevin, W. M., SNAL. CHEM.,25, 1612 (1953j1, the second line should have listed ruthenium instead of rubidium. I n the article on “Catalytic Activity of Cysteine and Related Compounds in the Iodine-Azide Reaction” [Whitman, D. W., and Whitney, R. McL., Ax.4~.CHEM.,25, 1623 (1953j1 in the fifth paragraph under reagents, the iodine-azide solution should be 0.10W.
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