Determination of Thorium and Its Separation from Uranium by Ferron D. E. RYAN', W. J. MCDONNELL, AND F. E. BEAhIISH Department of Chemistry, University of Toron t o , Toronto, Ontario, Cannda
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The following report deals with the development of a method for the prakimetric determination of thorium and its separation from uranium by means of ferron (7-iodo-8-hydroxyquinoline-5-sulfonic acid).
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PROC EDU R E
METHOD for the quantitative determination of thorium in the presence of uranium was required. Of the, estahlished methods of separation only the oxalate method was considered applicable, but it was rejected because of occlusion of uranium by micro amounts of thorium oxalate. Precipitation and separation by the ferron method
Samples (9.98 ml.) of the standard thorium solution mere measured by means of a pipet into 100-ml. beakers and the pH of the solution was adjusted to within the range 2 t o 3.5 with ammonium acetate and hydrochloric acid solution. The samples were placed on the steam hath and, after 10 minutes, 25 ml. of 0.2% ferron solution were added (approximately 2 ml. of reagent being required for each milligram of thorium present). The pale vellow precipitate was allowed t o digest for a half hour on the ;team bath. The precipitate was filtered through a S o . 42 Whatman 9-cm. filter paper, chaned by means of an infrared evaporator or a burner, ignited in a muffle at 900' C., and weighed as thorium oxide. Some of the results are rerorded in Table I.
?H
SOjH
COMPOSITION OF THOKIUW-FEHRON COMPLEX
Ferron reagent was added to a large excess of thorium in 100 ml. of solution in order to prevent adsorption of the reagent itself on the precipitate. The beaker and contents were placed on the steam bath for a few minutes and the precipitate was then filtered through a previously weighed filter crucible. The crucible was placed in a weighing crucible bottle and dried t o constant weight a t 110" C. The dried precipitate was then placed in a muffle and slowly ignited to the oxide. The average value obtained for the thorium content was 23.88%. The theoretical value of a 1 t o 2 ratio of thorium-ferron iq 24.8y0',.
were effected in much less time and required less manipulation than with the oxalate procedure. In the case of microdeterminations the greater volume of the ferron-thorium complex offered a n advantage over the thorium-oxalate. The 8-hydroxyquinoline method also possesses this advantage but uranium is precipitated. During the investigation of the suitability of various organic compounds it was found that ferron precipitated thorium but not uranium under specific conditions. Ferron was first used quantitatively by Yoe ( 4 ) for the colorimetric determination of iron. He described it' as a specific reagent for trivalent iron and records noninterference from over 60 metal ions, among which were the rare earth elements, vanadium, columbium, and tantalum. He found that ferron appeared to precipitate copper quantitatively. Swank and Mellon ( 3 ) studied in detail the ferron-iron method and reported interference from various anions and cations through soluble complex formations. Fahey (1) used this interference by fluorine for its colorimetric determination. Yoe and Hall ( 6 ) confirm the effect of copper and record the interference of highly colored ions. They recommend the preliminary removal of insoluble and readily hydrolyzed hydroxides such as tin and titanium.
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Table I.
Determination of Thorium and Separation from Uranium by Means of Ferron
Expt. NO.
1 1 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
The authors have determined that, under the conditions described below, there is no precipitation with lanthanum, cerium, titanium, nickel, and cobalt. Silver, mercury, and copper are precipitated by ferron in the pH range suitable for t>horiumprecipitation. REAGENTS
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Ferron, 2 grams of ferron (Eastman Kodak S o . 4449) dissolved by heating with 1 liter of water. The solution was filtered t o remove any suspended material. Ammonium acetate, 10 grams of reagent grade ammonium acetate dissolved in 100 ml. of water. Hydrochloric acid, concentrated reagent grade. Sitric acid, concentrated reagent grade. Thorium nitrate solutions, standardized by the oxalate method (2). ,One solution contained 10.21 mg. and the other solution contained 10.02 mg. of thorium per 9.98-m1. sample. Uranyl nitrate solution was standardized by precipitating the diuranate and contained 47.8 mg. of uranium per ml. of solution.
52
23 6 7. 8:9.
PH 3 5 3.5 2.6 2.4 2.0 2.4 2.4 2.4 2 ;L4
... ... ...
...
... ... ... ... ... . . ... ...
Thorium Added
Thorium Recovered
Uranium Added
Mg.
MQ.
Mg.
10.21 10.21 10.21 10.21 10.21 10.21 10.21 10.21 10.21 10.21 10.21 10.02 10.02 10.21 10.21 10.02 10.02 10.02 10.02 10.02 10.02 10.02 10.02
10,22 10.23 10.18 10.21 10.19 10.44 10.54 9.82 9.79 10.23 10.22 10.03 10.01 10.22 10.19 10.24 10.22 10.69 10.81 10.00 9.98 10.01 10.04
2oJ 20.
24 24 24 24 30 40 30 50
50 100
Obtained with unfiltered ferron reagent. Obtained when precipitat
1-5. Indicate that thorium is precipitated quantitatively by mt ferron. 16-17. Obtained with Whatman filter pulp to aid in filtering. Very satisfactory for thorium alone but tends to cause occlusion of uranium. 18-19. Indicate that with larger quantities of uranium present occlusion. of uranium occurs. Confirmed by direct testing of precipitate. 20-23. Show that thorium can be separated from large excesses o f . uranium b y double precipitation. a Bromophenol blue indicator used. Blue color was first developed with) ammonium acetate and dilute hydrochloric acid added to give yellow color.
* Present
address, University of New Brunswick, Fredericton, New Brunswick, Canada.
416
J U N E 1947
417
SEPARATION O F THORIUM FROM URANIUM BY FERRON
The following method proved satisfactory:
Complete precipitation of thorium can be obtained by the addition of 2.0 ml. of reagent per mg. of thorium in 1 ml. of solution. \Then uranium is present, however, it is difficult to d e t e ~ mine the exact quantity of reagent necessary, as a colored uranium-ferron complex is formed also. If 25 ml. of reagent solution in excess of that necessary to produce the first permanent precipitate are added, the thorium cnn he completely precipitated. Procedare. Sanip1c.s of t lit: standard tho!,i,Irii wlution '~verc' measured by means of a pipet into 100-ml. beakers, and "salted" with varying amounts of uranium, and p H x a s adjusted in the range 2 to 3.5. The samples were placed on a steam bath and, after 10 minutes, 0.27, ferron solution was added. The precipitate was allowed to digest for a half hour, filtered through KO. 42 F'hatman filter paper, ivashed ivith the reagent solution, ignited, and weighed a s thorium oxide. R e d t s are recorded in Table I. Reprecipitation Method. Since uranium !vas occluded when amounts larger than tn-ire that of thorium xvere present, a double precipitation was attempted. The precipitate was dissolved by hot, 2 S hydrochloric acid, the pH adjusted within range 2 to 3.5, a,nd precipitation carried out as previously described. I n all cases only 90% of the thorium was recovered even \%-henn o uranium was present. The usual methods of destroying organic matter could not be used. Oxidation with perchloric and nitric or sulfuric and nitric acids or charring with the infra-rediator was unsatisfactory because of the formation of int,erfering substances. Interference of sulfate ion was indicated by the fact that ferron failed to produce :t precipitate when the ferron-thorium complex vias destroyed with a sulfuric-nitric solution. This was confirmed by adding alkaline metal sulfates to thorium solutions, in ~vhich c n ~ e sferron produced no precipitate.
The samples, after the first precipitation, were filtered through filtering crucibles and heated for 1 hour a t 550 to 600' C. The temperature and time are important. If heated below this temperature sulfur was not volatilized and sulfate was formed on the addition of nitric acid. If heated for too long at this temperature an overburned oxide was formed which was dissolved with difficulty. The residues in the crucibles were then washed into their original beakers with dilute nitric acid and evaporated to dryness. Three evaporations were made, first with 10 ml. of concentrated hydrochloric acid and 5 ml. of concentrated nitric acid, second with 5 ml. of concentrated nitric acid, and finally with water. Ten milliliters of water were then added and the precipitation carried out as previouPly described. Results are rhown in Table I. C ~ N LU C sion
Thorium can be quantitatively precipitated by ferron in the p H range 2 to 3.5 and may be separated from txvice its amount of uranium by a single precipitation. With larger proportions of uranium a double precipitation is required. Sulfate ion interferes in the precipitation of the complexes. LITERATURE CITED
(1) Fahey, J. J., IND.ENG.CHEM.,ANAL.ED.,11, 362 (1939). (2) Hecht, F., and Donau, J., "Reine und angewandte Mikrochemie in Einaeldarstellungen. Bd. I. Anorganische Microgewichtsanalyse," p. 210, S'ienna, Juliua Springer, 1940. (3) Swank, H. IT,, and Mellon, M.G., ISD. ENG.CHEM.,.&SAL. ED., 9,406 (1937). (4) Yoe, J. H., J . A m . Chem. SOC.,54,4139 (1932). ( 5 ) Yoe, J. H., and Hall, K.T., Ibid., 59, 872 (1937).
Determination of Oxygen in Steel by the Vacuum Fusion LEROY 4LEX iYDEK1, U
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i\IPKK4Y2,
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E. Q. 4 S H L E I , Generul Electric C o m p a n y , P i t t s j i e l d , Mass.
4 simplified ,acuum fusion apparatus for the determination of oxygen and a modified operational plan are described. Relatively continuous operation is achie\ed, with consequent sa\ing in analysis time. The need for minimizing surface oxidation and contamination during the preparation of the analytical samples is discussed. 4 method for the measurement of oxygen and hydrogen in surface films is dewrihed and illustrated.
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T
H E vacuum fusion uic.thod f o r rhc tiPtrrrriillatiori of oxyger1 in iron and steel by the convrrsion of the oxygen present t o carbon monoxide at a high tempwature has attained international acceptance. The simplified apparatus described in thih 2trt,icle has been successfully used over a period of nine months for the analysis of comniercial 3.5'5 silicon steels. Because of a nerd for quantity output, efforts have been primarily directed t oward simplification of the equipment and improvement of operating technique. -1lthough it was not expected that' data of uniquely high precision and accuracy would be obtained, the 2tnalysis of eight standard steels (I@, reported below, has demonstratcLd that highly satisfactory result,s can be had with thv prcwnt rquipment. The quality of the results has been improved by minimizing contamination and surface oxidation during the preparation of samples for analysis. I n fact, this hits bwn found to be a prime rt:quisit,e for success in the st'udy of specimens possessing a large surface-i.e., thin rolled strip or sheet. 1 2
Present address, LIellon Institute, Pittsburgh, Pa. Present address, Southern Research Institute, Birrningtiaru. A l a .
During the nine months since the apparatus was placed in service 354 steel samples have been analyzed. The actual time of operation has been somewhat, less than one half of t,he working hours during that period. Of these analyses 267 were complete determinat,ions of hydrogen, oxygen, and nitrogen, while 87 were estimates of oxygen from measurements of the total gas extracted. This rxperience has shown that after a short training period a capable high-school graduate ran perform the required operations and obtain reliable results. DESCRIPTION O F APPARATUS
Figure 1 is a photograph and Figure 2 a schematic diagram of the vacuum fusion apparatus. Furnace. The steel samples are melted and the oxides reduced in the graphite crucible, G, which is supported by the loosely packed bed of graphite powder, 0. This powder also thermally insulates the hot crucible from the water-cooled quartz tube, Q. The water-cooled copper coil, N , supplies the high-frequency field which induct,ively heats the crucible. I t is energized by a General Electric 5-kva. (output) power oscillator, Model 4F5.44, which furnishes a field of 550-kc. mean frequency.
