V O L U M E 2 1 , NO. 11, N O V E M B E R 1 9 4 9
1325
Erlennieyer flask. Add 5 1111. of concentrated nitric acid arid 30 ml. of 70% perchloric acid, bring to gentle boiling, and continue for 1 to 1.5 hours after initial evolution of dense white fumes of perchloric acid. D o not cover the flask during this decomposit,ion. Cool, and add 15 ml. of water, then 5 ml. of 3% hydrogen peroxide. \$-arm gently for several minutes to clarify the solution. If the bulk of the gelatinous mass of phosphates obtained upon addition of water does not redissolve, add 5 to 10 ml. of concentrated hydrochloric acid. These phosphates may not readily dissolve if an excessive amount of perchloric acid is evaporated during the decomposition period instead of being returned by reHux action. However, a solid residue of zircon, uartz, rutile, ilmenite, and dehydrated silica may be present.. 8001the solution, then filter to remove this residue, and wash thoroughly with cool 1 to 3 nitric acid. Precipitation of Thorium and Rare Earth Oxalates with Methyl Oxalate. Evaporate the filtrate obtained from the perchloric acid decomposition to dense white fumes in a 600-ml. beaker. Cool, and add 50 ml. of water, followed by 5 ml. of 3% hydrogen peroxide. Warm gently for several minutes until the solution becomes clear, then add 100 ml. of water. Cool this solution, then add concentrated animonium hydroxide dropwise to the appearance of a small amount of gelatinous precipitate which does not redissolve. Quickly add 10 ml. of concentrated hydrochloric acid and allow the solution to stand for 5 minutes. Add 6 grams of methyl oxalate. Employ mechanical stirring and warm gently, 70" to 85" C., and continue for 30 minutes after the initial precipitate appears. Then add a hot solut,ion of 8 granis of oxalic acid in 200 ml. of water. Stir and keep warm for an additional 30 minutes. Cool this solution to room temperature, then adjust the pH to 0.8 to 0.9 by the dropwise addition of dilute ammonium hydroxide. Filter through an ashless filter paper and wash ten times with a cool 2% oxalic acid solution adjusted to pH 1.0 with hydrochloric acid. Do not attempt to transfer the bulk of the precipitate but wash by decantation as much as possible. Transfer the filt,er and precipitate back to the 600-ml. beaker containing the oxalates, then proceed as directed in the urea method (6) for the reprecipitation of thorium and rare earths with methyl oxalate. Separation of Thorium from Rare Earths with Tetrachlorophthalic Acid. Cool the solution of thorium and rare earth perchlorates obtained from the second methyl oxalate precipitation. Add 200 ml. of water and 1 gram of sodium iodide, then :Idjust the pII to 1.5 to 1.6. 9 d d 200 ml. of a solution of tetrachlorophthalic acid containing 3 grams per liter. This amount of acid represents 2.5 times the theoretical required to precipitate 0.1 gram of thorium oxide. Adjust the pH to 1.0 to 1.1. Place the beaker on a temperature-controlled hot plate designed to reacli 70" to 80" C. Employ rapid mechanical stirring. The precipitate will begin to form in approximately 20 minutes for amounts of thorium oxide in the range of 50 to 100 mg. Complete precipitation will be effected in 1.5 hours after initial formatioil. Where t he amount of thorium is considerably less than 50 nig., the initial precipitate may not appear for 1 to 2 hours or longer. Filter the hot solution, then wash with a cool 0.1 % tetrachlorophthalic acid solution adjusted to pH 1.5 with hydrochloric acid. Do not ottc,mpt to remove w c r y trace of precipitate from the
2nd Annual Summer Sumpoxium
Table IT.'. .4nalysis of Jlonazite Sand Urea Sample 1 2
Sample Gram8 1.2325 1.1413
Av.
ThOl
R 7.84 7.79 7.81
Tetrachlorophthalic Acid Sample Tho* Grana 70 1.7350 7.76 1.1215 7.76 7.76
beaker walls. Next convert the thorium salt to insoluble hhdrous thorium oxide by treating the precipitate with hot 2% sodium hydroxide. Wash the stirring rod, beaker walls, and filter paper a t least ten times with this solution to remove the sodium tetrachlorophthalate. Redissolve the hydrous thorium oxide with hot 2 LV- hydrochloric, acid, catching the filtrate in the original precipitation beaker Kash the stirring rod and beaker walls with the hot acid. Reprecipitate the thorium with tetrachlorophthalic acid as ir, the previous case. Transfer the precipitate quantitatively to 3 previously ignited and weighed S o . 3010 Selas crucible. Wash thoroughly with a cool 0.17, tetrachlorophthalic acid solutioir adjusted to pH 1.5. Dry the crucible a t 110" C., then place in a cold muffle furnace and slowly raise the temperature to 350' C. and hold for 45 minutes. Next slowly raise the temperature to 850 O C. and hold for 1 hour. Weigh the precipitate as Tho2. ANALYSIS O F A MONAZITE SAND
The sand taken for anal;-sis was of Indian origin. It war ground to a 100-mesh size, t'hen analyzed by both the urea and the tetrachlorophthalic acid methods. Data obtained are giver. in Table IV. ACKNOWLEDGMENT
The authors wish to t h m k Irving Nickerson of The Ohio Statr Cniversity for his assistarice in the early stages of this investigation. Thanks are also due the Siiigara Alkali Compmy, Niagara. 9.Y., for kindness in making :ivailnl)lr? the tetrachlorophthalic. arid marketed as Siagathal. LITERATURE CITED
(1) (2) (3) (4)
tiordon, L., arid Caley, E. R., A N A L . CHEM.,20, 560 (1948) Metsger, F. J., J . Am. L'hem. SOC.,24, 901 (1902). Smith, J. O., and Jained, C., Ibid., 34, 281 (1912). Willard, H. H., and Fogg, H. C., Ibid., 59, 2422 (1937).
( 5 ) Willard, H. H., and Freund, II., IND.EX. CHEX.A N A L . ED.,18
195 (1946). (6) Willard, H. H., and Gordon, L., -Ax.
