|× № ſá ， ſ. O |- №. ſ. C. -- ſº “EMPIRE” Single Hinge | Spring Back Sheet Holder NO. L75C19 Size 11" x 8%" 1 inch Spring The following sizes carried in stock: Number {S Q, T No. Size J7 L7505 68 4% x 8% ºf - L7506 69 5% x 8% } 3. § ºt L7507 61 L7508 62 Bound L75012 63 Full L75014 64 Canvas L75018 67 L75019 66 L75023 65 " - wº - - - - * - * * * * * * * - - - - - - * * * * * º - - - *** * * * * * - - - - - - * * * * - - - - tº --- * … º. w wºw wº in the University of Michigan R. J. Carney. ažite Sand. Size of Sample. . Methods Requiring the P Accuracy of the Todate Method. Development of the Pyrophosphate Method Solubility of Rare Earth Pyrophosphates. . . Previous Mention of Thorium Pyrophosphate. . . Properties of Thorium Pyrophosphate . . . . . . . Conditions for Complete Precipitation. . . . . . . Ignition of Precipitate Methods for Conver 81 on Of Thorium Pyrophosphate to Hydroxide and oxalate. . . . . . . . . . . . New Method for OXidat iOn Oſ Filter Paper' . . . . . Purification of Thorium Nitrate. . . . . . . . 8 Experiments ShOWing COmplet ene SS Oſ Precipitation . . . • e ſe e e e & º e Appl ication t;O Monazite Sand. Necessary variation 1n Method. * Test ing of Oxide. Advantages of Method. vestigation of Published Methods. Determination of Purity of oxide. Sodium Thiosulfate Method. . . • - Metanitrobenzoic Acid Method. Lead Carbonate Method. . . Potassium IOdate Method. . e • . . Sebacic Acid Method. . . . Ammonium Molybdate Method. . . . . Sodium Hypophosphate Method. . . . . 8odium Pyrophosphate Method. . . . . Summary. BIBLIOGRAPHY. - following is a complete consulted. The page º which the reference is 13 Beilstein, Handbuch der organ º: anorg. Chem. o (1894). : ischen Chemie, 4.- :- 297 (1902). Pages 3 and 20 ** Blomstrand, Z. für Kryst., 6, 160 (1887) and 20, 367 (18 Böhm, Seltene Erden, (2), 89. - -- Borelli, Gazz, chim. Ital. , 39, [1], 25 (1909). Pages 22 onyaenius, Chem. Zentr., 1863, dº." º º "… Cleve, Bull, soc. chim. , [2] , 21, 116 (1874). Page ‘. . . ; ; ;º. 3 ºr º º , º, º 4. 1onary of Chemical solubilities, 313. Page 5. - COmey, Dict COrne, J. Phar. Ohim., US), & , 123. Page 31}. Dennis, J. Am. Chem. Soc., 18, 947 (1896). Page 3. Dennis and Kortright, Am Chem. J., 16, 79 (1894). Page 3. Drawe, Ber., 21, 3Hol (1888). Page 34. - --> *... Drossbach, Z. angew. Chen., 14, 655 (1901). Pages 3 and 20. Fresenius and Hintº Z, Z. anal. chem., 35, 525 (1396). Page 20. Giles, chem. News, 92, 1 and 30 (1905). Page 27. - - Glaser, Chem. Ztg., 20, 612 (1896). Page 3 3 and 20. Gmelin-Kraut, Handbuch º, Hauser – See Meyer. ; -. --- ----- * **** , - . Hauser und wirth, Z. angew. Chen., 22, H8+ (1909). Pages 3 and 26. Hintz – See Fresenius. º * * Hintz und Z. anal. Chem., 36, 27 (1897). Pages 3 and 20. Hübner, Ann., 222, 72 (1881). Page 24. James – See 3m.1th. - - Kortnight – see Dennis. Koss, Chem. Ztg., 36, 686 (1912). Kress and Metzger, J. Lecoq, chem. Soc., 37, 2338 (1915) Page 17 º º - er, J. Am. Chen. Soc., 21, 901 (1902). Metzg - J. Ind. and Eng. chem. , 1, 193 (1912 3 and 29. * . -- - ... - ... --- Meyer, Z. anorg. or wº săuren. Pages Meyer und Speter, chem. ztg., 34, 306 (1910). Pages iſ and 27 Mineral Industry, 22, 510 (1913). Page i. Moissan, Traité de chimie Minérale, 3 , 8.8l. Page 5. Mulder, Ann., 311, 297 (1310). Page 24. Neish, J. Am. Chem. Soc. , 26, 780 (1904). Pages 3 and 24. Penfield, Am J. Sci., 211, 250 (1332) and 36, 322 (1888 ). Page l. Philipp, Ber. , 16, 719 (1333). Page 311. Pinkster º- See Rosenheim. Rosenheim, Chem. Ztg., 36, 821 (1912). Pages H and 33. Rosenheim und Pinkster, Ber. , 13, 2005 and 2007 (1910). Pages 34 and 35. - - - Rosenheim ind Triantaphyllides, Ber. , 13, 592 (1915). Page 38. Ruheſmann — 366 3kiinner”. Sälzer, Ann. , º 19 l ( 1332). Page 33. James, J. Am. Chem. Soc. er – See º See Hauser. Wyrouboff et Verneuil, Compt º soc. chim. (3], 19, 219 (1898). Pages 3 and 8. The mineral, monazite, is considered to be a cerium phosphate, Cepo., 1n which a part of the cerium is replaced b other rare earth elements, such as praseodymium, neodymium aſ lanthanum. It contains also a variable amount of thorium has received much attention’. From the work of Kress and Metzger it seems probable that 1 t is present as a phosphate By the disintegration of rocks containing natural process of sorting and concentration by the action of water, the lighter minerals being washed away. This mixture of monazite with other heavy minerals is called monazite sand. A large part of the supply of monazite sand is mined in Brazil, where it occurs along certain parts of the seacoast and has been concentrated by the action of the waves. In the Uni º States the sand occurs in North and South Carolina, but it has not been mined there to any extent since 1910" The valuable constituent is thorium, which is extracted * * * * * * * * * * * - - -º- - - * 2. Penfield, Am. J. Sci., 21, 250 (1382); 36, 322 ( 1383 ); Blomstrand, Z. rur Kryst., 6, 160 (1887); 20, 367 (1892). soc., 31, 610 (1909). - 3. J. Am. Chem H. Mineral Industry, 22, 510 (1913). minerals, monazite is at the present tim the O. cial importance. Thorium nitrate is used in the manufacture gas mantles, a mantle consisting mainly of thorium oxide, whic is readily obtainable from the nitrate by 1gnition. When the importance of thorium in the gas-ligh º ry 1s considered, the necessity for an accurate and con method for it, S quantitative determination in monazite sand apparent. Several years ago Professor E. D., thorium pyrophosphate is considerably less soluble in acias the the pyrophosphates of the other rare earth elements - under his airection, undertook to use this ract in the ---------------- or a new method for the determination of thorium. In the course of this work, all of the previously published methods were tried, and it became evident, that a thorough investigation of the subject ºn º was advisable. This thesis present a the development of the phosphate method and the results obtained in th C. ox.” **... --- ***-*…*.*.*.*.*.*.*** A high degree of accuracy/1s necessary. Meyer and Hauser" / of the other published methods. State thi S requirement to be that the result shaāl not vary from the correct number by more than 0.05%. In some cases the methods do not ſulfill this requirement. Thorium may be lost during the sº º . . . . . . . . tº . . . . . . . . . . ------- * analysis, and the precipitate may contain other rare earth elements. Cerium is especially likely to be present in the final precipitate on account of 1 ts tendency to become oxidized to the tetravalent - . . . . . . . - A ſºuveva . . . . . . 7. fr s state, in which condition the solubility of 1 ts salts' is much the tº ºr ſº . . . - . . . . - same as the solubility of the corresponding thorium salts. The color of the final oxide 1s not an absolute criter10n of 1 ts * * * *-* was “ sºme * sºme sº-º-º-º- * * * * * * * purity'. Small quantities of praseodymium and n strong color, while considerable cerium can be present without It is recognized by good authorities*that a large Of the sand, 20 - 50 g. or more, should be taken. Methods in which CL - .." - small samples are used are subject to critism 1n this º The principal methods up to the year 1910 were the ammon- ium oxalate*, sodium thiosulfate", *hydrogen peroxide’, fumaric - º, 1 - - º - acid' and nitrobenzoic acid' methods. In all of these, as well as in the more recent volumetric molybdate"method, 1t 1s necessary to * precipitate all of the rare earth elements as oxalates from the solution of the sand, in order to separate them from the phosphoric ac1d. This precipitation and the subsequent treatment of the oxalate precipitate, in order to dissolve 1 t and obtain a nearly neutral solution of the rare earth salts, requires considerable time. Potassium hydronitride'ana sebaclºacid have been provo as reagent, S for the separation Of thorium from the other rare earth elements. A neutral or only slightly acid solution 1s re- quired, so these methods could not be applied to monazite sand 2 ----------------------------------------------------------...--...-- ******------------------------------ Without, first, precipitating with oxalic acid. - - - - - - - - - - - - - - - sºme -m - - - - - - - l. Hauser und Wirth, Z. angew. Chem. , 22, 1814 (1909). 2. Meyer und Hauser, D1e Analyse der seltenen Erden und der Erdsauren, 260. . Hauser und Wirth, Loc. cit. 3. Glaser, Chem. Ztg., 20, 612, (1896). H. Hintz und Weber, Z. anal. Chem. , 36, , 27 (1897). Drossbach, Z. angew. Ghem. , 111, 655 (1901). Benz, Ibid., 15, 297 (1902). 5. Wyrouboff et Verneuil, Compt. rend. , 126, 310 (1898); Bull. soc. chim. , [3], 19, 219 (1353). BenZ, LOC. C1 t . 6. Metzger, J. Am. Chem. Soc. , 24, 901 (1902). 7. Neish, Ibid., 26, 780 (1904) - 3. Metzger and Zons, J. Ind. Eng. Chem. , H. 1193 ( 9. Dennis and Kortright, Am Chem. J., lº, 79 (189 J. Am. Chem. Soc. , 13, 947 (1896). 10. Smith and James, Ibid., 314, 231 ( 1912). 1912) l!); Dennis, The only methods in which the , from the solution of the san, --------- the oxalate, are the 10date' method of Meyer and speter and he hypophosphate"method of Rosenheim. methods? - the todate method gives very accurate results. Me speter have tested the method on pure solutions and on a which had been analyzed in the laboratory or Dr. Gilbert, Hamburg, in which laboratory the det erminati ons for the Germ thorium 1ndustry are made! The results obtained agreed 8. 1- ly With the result of Dr. Gilbert. Thorium pyrophosphate has been mentioned very little in the literature. Cleve; in 1874, in a paper on thorium salts, made l. Meyer und speter, ohen. Żt g . , 3%, 306 (1910). 2. Rosenhein, 1914, 34, 321 (1912). 3. Meyer und Hauser, Loc. cit., 263. H. Meyer und speter, Loc. cit. . 5. Gieve, buil, soc. chim. . [2], 21, 116. Na. Th(Pao, )2.2H2O. The various chemical manab, ies' give these formulas and refer to the article by striking difference in the solubility of the pyrophospha acids has apparently not been noticed. - the normal sodium salt, sap.or.io Hao, is the vement pyrophosphate to use ror precipitating the thorium inexpensive and is readily obtained. A water solution of t salt 1s very stable, and there is no appreciable hydrolysis t orthophosphate even arter standing for a long time or on heating? thorium pyrophosphate dissolves readily on heating an excess of sodium pyrophosphate. It aissolves with arriculty in a large excess of pyrophosphoric acid and is precipitated from this solution slowly by heating, and rapidly by adding a stron acid and heating. It is soluble also in ammonium carbonate and - - in alkaline OXalate solutions. From solutions of the aouble pyro- phOSphate, thorium is Completely precipitated by boiling with an eXce SS Of SOdium hydroxide. It is not precipitated from this solu- tion by ammonium hydroxide or by oxalic acid; if the solution i strongly acidified after adding oxalic acid, a mixture or oxalate and pyrophosphate is precipitated. The addition of a strong acid to the double pyrophosphate breaks 1 t up and causes the precipi- tation of thorium pyrophosphate. - In Order to precipitate thorium completely as the pyro- phosphate, the solution must be boiled arter adding the sodium. i | ; | . | : ſº (a Alpitate and 1&niting for about - ſº pyrophosphate, milligrams Of otherwise a few - -sº º º *: ºf hould be about 0.3 N or equal to acid (1.19) in solution. The acidity s - ºf lºº # º in of hydrochloric 200 cc -- º -- 1s very much too low, some thorium may fall to be prec " ** - º, º: º * , * & ºf ºr..." ºr * - ſº, the form of the * † - * * * * * * .* *: #4 ºf gº - - - * ... - *---- … * … º.º. ºf - º º º º - going into ºf ºz. * * * * * * * * - - º - dOuble pyrophOSphate ; º: , , ſº º ºx. solvent errect of the acid comes into play. The acidity may, vary within fairly wide limits without the loss of any º ſº º º * º: Zirconium 1s comple --- ever, tely precipitated from 8. solution thorium. º: . . . . . ºf . under the same conditions as thorium. - º - º † : * & ------- The pyrophosphates of the other rare earth elements are also soluble in an excess of sodium pyrophosphate. They dissolve *- º º readily in a few ce. of dilute hydrochloric acid. on adding bron- * -- … } ºr a … º.º. - ºr º, ºn - tº Or . º * , ine water to the solution of cerous pyrophosphate in hydrochl acid, a white precipitate of ceric pyrophosphate forms immediately. º # * * * * ...º …t. - ...º 3. * * * * * * * º: Thorium pyrophosphate may be 12nited by drying the préc- paper, burning the paper at as low ºf , º, . 1pitate, removing 11 from the n adding the main body of the a temperature as possible, the . . . . . jº, en ‘Iſlinut, rifte es. Long-continued *- -ºš º 'º - ** -------- 1gnition causes a slight loss of Paos. As is the case in the 1sni- t iOn Of Other phosphates, 1t 1s difficult to burn off all of the ----- Carbon. Thorium Oxalate 1s readily changed to the Oxide by 1gni- tion. Since an oxalate precipitation 1S necessary at some point * } ºr ; ºr - * . . . . . . . . . . . . t in the analysis Of monazite sand in order to remove zirconium, zirconium oxalate being soluble in an excess of oxalic acid, it --. ---, -º-º-º: . º ºf a º º seemed advisable to precipitate the thorium finally as the oxal- ... : : º ate and 1gnite and weign the oxide. It was very difficult to find a really satisfactory , º, º f :: * - - º method ror changing the pyrophosphate quantitat, ively to Oxalate * 'tº tº . . . . or hydroxide. The first method tried was to change the pyrophos- *. º, ſº tº ºf phate to hydroxide by boiling With sodium hydroxide. Other thorium precipitates, for example the thiosulfate and oxalate, º:::::::::::::::::::::: * e1ng incomple: - method tried Was to dissolve the pyrophosphate in an War’ſ) sodium pyrophosphate, change the thorium to hydroxide y difficulty in washing out all of the soluble pyrophosphate fro the thorium hydroxide., several good results wereyh ed in this way. Similar methods applied to the solutions of the pyrophosphate in ammonium carbonate and oxalate were unsa ractory. - The next attempt Was to dissolve the thorium pyrophos- phate in coneentrated Sulfuric acid and oxidize the filter paper. Instead of the use of Sodium or potassium nitrate for this pur- pose, as is customary, ammonium perchlorate' was tried. It was found that in this Way a fifteen centimeter filter paper, contain- 1ng about 200 mg. or moist thorium pyrophosphate, is completely oxidized to carbon dioxide and water, the pyrophosphoric acid Changed to Ortho ac1d, and the thorium brought into solution in about, ten minute S. The dry paper, alone, can be destroyed in much less time. Using sodium nitrate, as in the hypophOSphate 4. - method, one or two hours would have been required. The amount of ammonium perchlorate used is small and the reagent 1s inexpensive. On COOling and adding Water to the mixture or concentrated sulfur- 1c acid and thorium sulfate and allowing 1 t to stand for a short time, a clear solution results. To change the thorium completely to an oxalate entirely free from phosphate, it was round best to fºrest change the sulfate to hydroxide by boiling with sodium hydroxide, filter this, dissolve 1t in hydrochloric acid and a- - - - sº sº sº * - - - - - - - * * * * * * *- - - * * * * * * - l. This suggestion is due to H. H. Willard. precipitate as oxalate. This was foun to gi factory results than neutralizing with annonium hya acid until the precipitate aissolves and precipitating acid, the procedure in the hypophosphate method. - This method was first tested on pure solutions salt by the method or wrouport and verneuii, consistin double precipitation of the thorium by hydrogen peroxide second precipitate of thorium peroxyhydrate was dissolved nitric acid and the solution evaporated to dryness. After disso ing the pure salt in water, the strength of the solution was determined by precipitating the thorium from a measured volume or ls to stand over night then filtering and 1gniting to the oxide. The cerium, praseodym the solution as the oxalate, allowing this to ium, neodymium and lanthanum salts were the double ammonium º nitrates. The sodium pyrophosphate solution was made up by dissolv- . . . . . . * * * * # , º, - gº º, * . . . . . . º º:-- ſ'. ing 25 g. of Naa Paov. 10 Hao in 500 cc. of water. The ammonium perchlorate was the commercial salt purchased from Kahlbaum this left a slight residue when dissolved in water, 1t was puri- fied by one recrystallization. ''' -º,-- º:--> º, sº ºf ... . . The completeness of the precipitation of thorium by sodium pyrophosphate 1s shown by the following experiments: To 35 cc. of pure thorium nitrate solution, 5 cc. of Hol (1.19) were added, and the solution alluted to 200 cc. It was then heated to boiling and 10 cc. of the sodium pyrophosphate SOlult iOn were dropped in slowly from a pipet with constant stir- Ying. The solution was then gently boiled for r1 º ve minutes, stir- ring occasionally to keep the precipitate 1n suspens1on. The pre- * *-*- - - * * * * *** - * * *- - - - - -...- - - - ºr º- * * * * - - * * cipitate was allowed to settle for five or ten mi º º utes a then filtered' and washed with water raintly acidified chloric acid (one or two drops of acid in 200 cc.). The pap ſº ; : * * * * * º tº º º *::::: - * - " - “... --→ *-º-º-º-º-º-º-º-º-º-º-º-ººººº... º. º. ºº containing the moist precipitate was put into a 125 cc. 5 --- ºf sº, ** * * * * * flask, and 15 cc. of sulfuric acid (1.84) and a few crystals of ammonium perchlorate were added. The flask was then covered a watch glass which was held slightly away from the top or flask by three small bent glass rods in order to allow escap gases. The flask was heated gently and the heating continued un- - ºf , ºf . . . . - - . . .." º tº º º til a brown solution was obtained. The flame was then removed for 8. moment and more ammonium perchlorate carerully added. Heating was then resumed. More perchlorate was added when necessary. In a short time the solution became colorless and the carbonaceous - Jºº. ... `------------..... . matter had been entirely oxidized. The solution was then allowed *-n- t;O cool, the flask was placed 1n cold water and about 75 cc. of º distilled water were slowly added with stirring. In a short time º a Clear SOlution resulted. Thi S SOLUIt iOn was poured slowly into _-T- -----------------------------,------------- `-- - º - is ..." --- - - -º-º-º-º-º-º-º: **- a solution of 30 g. of sodium hydroxide in about 125 cc. of water, SOdium hydroxide solution. The SOlllt, 1 On Was St. 1rred and boiled for several minutes to convert the thorium to hydroxide. The hydroxide was filtered on a hardened filter paper, using silent auction.* was washed thoroughly with hot water. The paper and the precipitate Were placed in the beaker in which the hydroxide precipitation was made, and 5 cc. of hydrochloric acid º (1.19) were added. This was allowed to remain in contact with the - - - - - --- *------------------- * * l. Thorium pyrophosphate offers no alrriculty in filtration; the much more bulky Orthophosphate, however, is very hard to filter. 2. A Kjeldahl flask was later found to be preferable, as it º -º-º: eliminates all chance of loss by spattering. paper for a short time and then the solution ed. The paper was filtered orf and washed thoroughly ſ: - - of 2 g. of oxalic acid was added to the filtrate and thi . . . . - - . ..., ºf * º: º º * . . - -* - º º º - diluted to 150 cc. and allowed to stand warm over night ate was filtered, washed with water raintly acidified wi chloric acid, and 19nited to ºxide. The weight or tho, ta 0.1376 g. The amounts round in three experiments were: g., (2) 0.1374 g., (3) 0.1376 g. The filtrate from the thorium pyrophosphate gåWe no precipitate on b 111ng wit sodium hydrox- -- º'. . . . . . . . . . . . . . . ... -----. de, or on adding oxalic acid and allowing ºf , º, º, … --> * * * * * * ide or ammonium hydrox1 to stand. - Experiments were then carried out to determine if a quantitative separation of thorium from the other rare earth elements can be obtained by one precipitation with sodium pyrº phosphate. The acidity and volume of the solution were the same º, º as in the previous experiments: Experiment 1. - weight of Thoa taken: 0.1376 g; ; weight of Geoa taken: 0.1235 g.: weight of Thoa round: 0.1413 g. weight of Geoa carried down with the thorium was 3.7 mg. - - - - Experiment 2. — weight of Thoa taken: 0.1376 g.: weight Of Pr40, taken: 0.1241 g.: weight of Thoa found: 0.1409 g. weight of Pr407 carried down with the thorium was 3.3 mg. * . - Experiment 3. - werent of tho, taken 0.1376 e. weight of Nd2 08 taken: 0.1240 g.: weight of Thoa found: 0.1392 g. weight of Nd2 03 carried down with the thorium was l. 6 mg. º The oxides in Experiments 2 and 3 were quite strongly colored. º It was seen that a second precipitation of the thorium as pyrophosphate would be necessary in Order to remove the small amount, S Of rare earth salts that are carried down. The reprecipi– * tation was easily accomplished, the sulfate solu phate precipitate was rinsed into a beaker at added until alkaline. A rew arops or methyl orange were aa. hydrochloric acia aropped in until a neutral reaction va ea, then 7.5 cc. or hydrochloric acid (1:19) were adae solution diluted to 300 cc. The solution was heated to º - º, º: and precipitated with sodium pyrophosphate as before. The º phosphate was filtered, washed, and converted to sulfate, ide and oxalate in the manner previously described. In a number of experiments this method was tried upon thorium salts alone, and a complete recovery of the thorium was made in each Case. when tried upon mixtures of thorium and other rare earth Salts, the thorium oxide Obtained was in all cases entirely pure. The results obtained are shown in the following table: º, Thoa taken. Geo, taken. Laaos taken. Pr40, taken. Ndaos taken. Grain. GI’8Iſl. Gram • --- 0.1376 0.1376. 0.1376 0.1376 0.1235 0.1376 0.21;70 O. 1376 a 0.1376 0.1376 0.1241 0.1371 0.1376 0.12% o.1366 * * * * 0.1240 0.1375 0.1376 - 0.1250 0.1241 0.1240 0.1333 0.1376 a 0.1376 0.1235 0.1250 0.1241 0.1240 0.137 H. The method was then tested upon Imonazite sand. The best º, º: ſº method for the decomposition º of the sand See Int o be king a 50 g. sample of the ur used by Meyer and speter, ta -- sand and decomposing it with 100 cc. or concentrated sulfur acid. The sulfates may then be dissolved in water, filtered, all ed to one 11ter, and aliquot portions taken for analys: cº portion should be diluted to 400 - 450 cc. in order to obtain acidity used in the experiments on pure solutions. on precip 1ng the thorium from this solution with sodium pyrophosphate, º, ºr º: small deposit of ceric pyrophosphate formed on the bottom of the beaker, and this was very difficult to remove. By diluting th solution to 150 cc. and adding 5 cc. of concentrated hydrochloric acid, this did not occur. In carrying out the method 1n the s manner as on pure solutions, many good results were obtained, but in some cases the results were slightly too high and the final oxide had a raint pink or brown color. This was caused by a trace of rare earth phosphate not dissolving in the hydrochloric acid # - and thus being carried along with the thorium. This was avoided by precipitating the sulfate solution with sodium hydroxide instead Oſ ammonium hydroxide, filtering and washing the precipitate and dissolving it in the proper amount of acid. This process, of course,' involves the use of an additional hydroxide filtration, but as the hydroxide 1s filtered with suction and the ſiltration and washing - are rapid, but little more time 1s required than 1n the other method. An experiment on pure thorium nitrate solution showed that no thorium is lost by this variation in the method; weight of Thoa taken was 0.1376 g., weight pe COV e1, ed. Wals o.1379 e. In the presence or a large amount of Cerium, such as is found 1n monazite sand, it was round advisable to add a little sulfurous acid solu- tion to reduce any ceric certum before precipitat ing the Second time as the pyrophOS.phate. º º follows: 50 g. of the sand are heated to about concentrated sulfuric acid in a thick-walled iron d1sh COInplete deCOmposit iOn 1s obtained'. This will require from hours. The dish is kept covered with a watch glass during 2. - - º żº heating. The excess of sulfuric acid 1s not driven off. T. ture is cooled and introduced slowly into about 100 cc. or water contained in a large beaker, which is also surrounded with **** cold water. The mixture is stirred with a wide spatula and allowed to stand until the sulfates are dissolved. The solution is then filtered through a folded filter paper into a one 11ter flask, the paper washed, and the filtrate alluted to the mark, or this solu- tion, 50 cc., equivalent to 2.5 g. or the sana, are measured out and placed in an 800 cc. beaker, 5 cc. Of iyarochloric acid (1.19) are added and the solution is aunted to #50 ce. This is starred and 15 cc. of sodium pyrophosphate solution (25 g. in 500 cc.) arºe slowly added. It is then heated to boiling, stirring*when near the boiling point, and 18 boiled sently for rive minutes, after which it is allowed to stand for rive or ten minutes ana is filtered. The precipitate’s washed several times with hot water containing one or two arops or yarochloric acid 1n 200 cc. It is on a Watch glass, cooling, adding water and examining the undecom- posed mineral fragments with a magnifying glas S. The characteristic appearance or undecomposed monazite can be readily recognized. 2. As a rule, arter boiling begins, no attention is required, as the precipitate does not tend to settle. º 3. This precip1tate contains about 15 mg. of oxides or rare earth 3, § elements other than thorium and zirconium. next transferred to a 250 ce. Kjeldahl riask , , , . . . . . . . . 1c acid (1.81) and a few crystals of ammonium perchlora º The flask is COV ered with a watch glass held away from the the flask by three bent p1eces of glass rod. The mixture is r º º changes to a brown liquid. More perchlorate * * º, º ed until 1 t º: * , º added and the heating is continued until the organic all oxidized'. The sulfate 1s always slightly yellow. The mi: is cooled to room temperature and, after placing the flask in water, 100 cc. of distilled water are slowly added. The sulfates . - :-- - - --- º * ::..., . . º º ºf º - jº . . . . . º - sº. . . ; . . will soon dissolve? The solution 1s rinsed into a solution of 30 g. or sodium hydroxide in about 125 cc. or water conta a 600 cc. beaker. The mixture is starrea and boiled for several minutes, and the hydroxide 1s then rintered on a hardened paper with the aid or suction. It is washed a number of times with not Water . The paper 1s then placed in the beaker previously used, 10 cc. of hydrochloric acid (1.19) are added and allowed to re- main in contact with the paper ror a short time, about 150 cc. or water are added and the solution is boiled. The paper 1s filtered orr and washed, and the filtrate is diluted to 400 cc. About 3 ce. of a saturated sulfurous acid solution are added, the solution iS heated to boiling, and the thorium is again precipitated just as before with sodium pyrophosphate; the precipitate 1s washed and changed to sulfate and hydroxide in the manner just described. *-* * * * * *-* -er - - - as- sº- ºr eº- ºr- ºr sease ester - tº sº sº * * * * * * * is not harmful. Heating should be discontinued promptly when the Organic Imatter has all been Oxidized ; if heated much longer, the perchloric acid breaks up, causing Considerable foaming. 2. In the case of one of our monazites, a Small amount of a green- ish blue powder failed to dissolve on adding water. This occured several times. In each case the final result was a few one-hundred- ths of a per cent too low. The following method easily overcame this difficulty: The precipitate was filtered on a small paper, Washed a few times, and W1th the paper put in a Small flask. The paper Was Oxidized and the precipitate brought into solution by heating With 5 CC. Of Sulfur 1C acid and a little ammonium perchlor– ate . This Was added to the main SOlut, iOn . This second sulfate is white and always dis water. Finally the hydroxide is dissolved in 5 cc hydrochloric acid, the solution is diluted and boiled º, ºf tº filtered off, and the thorium is precipitated from the r1. a solution of 2 g. of oxalic acid. The solution is diluted to about 150 cc., and 1s allowed to stand warm over night. The o 1s filtered, washed with water raintly acidified with hydrochlor1 acid, and 1s 12nited to the oxide. - º --- º º - - To determine the accuracy of the results, they were compar- ed with those obtained by carefully carrying out the 10date method. The Sand was decomposed and the SOlult iOn Iſlade up in the manner previously described. 100 ce., corresponding to a rive gran sample, WäS measured Out , 50 CC. Of concentrated nitric acid adaea, and the mixture cooled by placing in cooled Water. A solution Of 15 g. of potassium 10date 1n 50 cc. of concentrated nitric acid and 30 cc. of water was added, this solution having been previously cooled. The mixture was stirred frequently and allowed to stand for one-half hour. It was then filtered'. The beaker was rinsed out with a solution of 11 g. of potassium iodate in 100 cc. of dilute nitric acid and 1100 cc. of water. The same filter paper was used throughout the analysis. When the solution had all drained through, the precipitate was washed into the beaker with the 10date wash- 1ng solution. It was stirred with about 100 cc. of this solution and filtered again. Any lumps Of precipitate Were pressed out With al spatula. The precipitate was now rinsed from the paper int, O the beaker with hot water. The mixture was heated to boiling, and the *º-ºº: º precipitate was dissolved by the addition or 30 cc. of concentrat- ed nitric acid. The iOdate Was reprecip 1 tated by a Solution of * -- ºr- ºr- sº ºn sº sº see sºme sº- see sº sºme sº sº- a-e ss, sº assº" sº ºr sº- l. A 15 cm. S. and 8. filter paper, No. 589, 1s recommended. 6 H. g. of potassium 1odate in a lit, tº 16 hot water and ilute n1 acid, the solution being fully cooled before ri .ering. After filtering, the precipitate Was again transferred to the beaker with the washing solution and filtered once more. The precipitate W8 S then washed from the paper With water, and the 10date a ssolv- ed in hydrochloric acid with the aid of sulfurous acid'. The thorium was precipitated from the boiling solution by ammonium hydroxide, the hydroxide washed with boiling water until free from 10a1ae, dissolved in dilute hydrochloric acid, and precipitated with an eXce SS Of Oxalic ac 10 . The oxalate was allowed to stand washed and ignited. º filtered, Three monazite sands were analyzed by both of these methods, and the results were round to check very closely vonazite D. Pyrophosphate Method - - - 5.12 % Thoa 5.11 % 5.1 % " . 5. 10 % " 5. Hl # Monazite E. Pyrophosphate Method tº Iodate Method 5.70 % Thoa 5.68 %. Thoa 5. 70 % " 5.68 % " . 5.68 % " 5.69 % " 5.6% 5.64% 5.67% " * - - --- sº-º-º-º-º-º-e ºs-ºs-ºs---aº -- sº-º-º: sº gº ºssº-º-º-- - - - - - - as---f 1. It is best to heat With dilute hydrochloric ac1d and add the Sulfurous acid a little at a time unt, 11 just Unough has been added to reduce the 10date. If too much is added, the hydroxide filters Slowly. W 2. This OXide had a fairly Strong pink t inge. - Monazite F. Pyrophosphate Method 5.32 * Tho, 5.3 af- - , º, . . . . º The Oxide obtained in the pyr Op º - - ºr , - - , -, -, * all cases white. About 200 mg. of * , ; this oxide were fused with . -- potassium pyrosulfate and the melt was dissolved in water and test for phosphate 3 * * dilute nitric acid. This solution gave no . . . . . . . . . . * , ; ; - Another sample of the oxide was dissolved in the same way and test- cerium by neutralizing the solution, adding an excess of ed for ºf tº º - potassium carbonate solution until the soluble potassium thorium * , ". - † º ; * **, *, carbonate was formed, and then adding a 11ttle hydrogen perox1de! NO color W8 S obtained. as Short a -- * ** - can be completed in --- - * * re * * * The pyrophosphate metho * * ºr -º . . . ." sº - time as either of the two rapid methods. starting with the filter- º º ed Sulfuric acid solution of the sand, all Of the operations up º º: to the precipitat iOn of the oxalate can be carried out 1n about º, º, º '. - sº required º º: Seven hour S. The short time * : * --- and the cheapness of the Yminat iOn . l. Levy The Rare Earths, le5; Meyer, Z. anorg. chem., º, * 1, 97 J. An. Chen. Soc., 31, 2338 (1915) *** (y - K.3 Investigation of other Published Methods ----- -- In the following work a comparison of the results obtain- ed by the different methods is made, the purity of the final oxide is determined and also the completeness of precipitation. The 1dea was not so much to compare a large number of results from the sand as to investigate the foundation of the method, that is, whether the thorium is completely precipitated and the precipitate uncontaminated With Other rare earths. *: Methods requiring the precipitation of the rare earths as oxalates were carried out upon a standard solution of monazite earths, thus insuring uniformity of sample. This solution was made by precipitating a dilute sulfuric acid solution of monazite sana with an excess of oxalic acid, washing the oxalates several times - by decantation, then transferring to a filter paper and washing thoroughly with water raintly acidified with hydrochloric acid. The oxalates were then converted to nitrates by oxidation with fuming nitric acid and finally to chlorides by repeated evapora- tion with concentrated hydrochloric acid. The ary residue of chlorides was then dissolved in water, a small amount of insoluble matter filtered off, ana the solution allutea. This SOlut, 1 On was standardized by the 10date method. In every case When thi S SOLu- tion Was used, the aliquot port1on taken a S a Sample Was eV apOrat- ed to dryne SS On a water bath in Order? to remove any possible trace of free hydrochloric acid. The chloride solution was used, rather than the nitrate, because of the Statement Of Meyer and Hauser' that chloride Solutions are preferable t O nitrate in the thiosulfate method. -- The purity of the thorium oxide was determined in the * * * sº sº, sº sºme ºr * sº mean saar seas wº" ºr sºme sºr ºr * *- - following manner. A sample was put in a weighed platinum c ignited with a Meker burner for twenty minutes and then weigned. It was dissolved by fusion with potassium pyrosulfate and leaching out with dilute nitric acid. Any residue was filtered and fused again until completely dissolved. The solution was precipitated With ammonium hydroxide and the hydroxide was filtered and washed a few times with hot water. It was dissolved in thirty ce. or concentrated nitric acid, alluted with water, and the thorium was precipitated by adding a solution of six grams or potassium iodate. The total volume of the solution was about 300 cc. This was stirred repeatedly and allowed to stand cold for about two hours. The loaate was filtered and washed a rew times with the washing solution used 1n the iodate method. It was then dissolved in hydrochloric acid With the addition of just enough sulfurous acid to reduce all of the 1odine to hydriodic acid, and the thorium was precipitated in bOiling SOlut iOn by amonium hydroxide. The hydroxide was washed thoroughly, aissolved in 6 cc. of hydrochloric acid, diluted to 100 cc. and precipitated with an excess or oxalic acia. The oxal- ate was filtered, washed and ignited to oxide in the usual manner. In this way the pure thorium oxide present in the original sample Was obtained. This method, involving only One precipitat iOn as iodate, would not be satisfactory for the separation of thorium from large quantities of other rare earth elements, but it is an eXcellent Imethod for the analys 13 Oſ Slightly impure oxides. To test the method, samples of thorium oxide from the pyrophosphate method Were fused with potassium pyrosulfate and subjected t O purification by an 10aate precipitation as just described. The method was then applied to the pure oxide thus obtained. In One Sample 0.2498 g. was taken and 0.2493 g. recovered ; in the second 0.4983 g. was taken and O. 1984 g. recovered. 20 The methods are taken up in the order in which the - - - . . º º . . º **." º published. The ammonium oxalate method of Glaser' is not considered :* 2 ºf ºº e ... " º as it has been ShOWn to be very inaccurate Sodium. Thiosulfate - This method is due mainly to the work of Fresenius and Hintz’ in 1896 and Hintz and weber"in 1897. The authors do apply the separation to the analysis of monazite sana, but it Well known that it has long been used for that purpose. conflict- 1ng statements have appeared concerning the completeness of x the precipitation of thorium by sodium thiosulfate and the accuracy of the separation from the other rare earths. The precipitation has as a rule been considered as incomplete, and the filtrate from - the thorium thiosulfate has been precipitated by ammonium hydrox– ide, the hydroxides dissolved in acid, evaporated to dryness, taken up with water, and the precipitation repeated in order to recover the thorium. This greatly complicates the analysis on - account of the exceedingly bad filtering properties of the large hydroxide precipitate. Meyer and Hauser atate that thorium is completely precipitated from a neutral chloride (not nitrate) SOlut 1.On if the SOlut, iOn 1 S diluted and boiled for some time. The tºº, wº-ºº: author i S able to confirm this statement in regard to dilution and boiling, but it seems doubtful if the nitrate has any effect. Incompleteness Of precipitation 1s probably due t O t, OO great aC id— º † º ity and not to oxidation. Boiling destroys the thiosulfuric acid 1. Chem. ztg., 20, 612 (1896). 2. Hint, Z und Weber, Z. anal. Chem. , 36, 27 (1897); Drossbach, Z. angew. Chem., 11, 655 (1901); Benz, Ibid., 15, 297 (1902). 3. anal. Chem. , 35, 525 (1896). ( * * - \ lºw %k. ^---------- - :* -. A r", a -r ‘. t '. Aº Aº *…*&^* \ . . ** ! * § C *-i- The method' was carried out as follows: 100 cc. of th tº. standard monazite solution were evaporated to dryness on a water bath and the residue dissolved in 250 cc. of water. This was heat- ed to boiling and a boiling solution of 9 g. of sodium thiosulfate added. The resulting solution containing the precipitate was boiled :- for thirty minutes. It was then filtered and the precipitate washed. This was boiled with 100 cc. of hydrochloric acid (1 - 3) for abou 15 minutes, the solution filtered and evaporated to aryness. The residue was taken up with 200 – 250 cc. of water and precipitated - just as before with a solution of 5 g. of sodium thiosulfate. After filtering and washing, the precipitate was dissolved by boiling With 10 CC. Of hydrochloric acid and 25 — 50 cc. of water. The residue of sulfur was filtered, the filtrate neutralized with ammonia and then made acia with 5 cc. of hydrochloric acid; it was then diluted and precipitated with oxalic acid. The oxalate, after standing, was converted to oxide by ignition. In Sample 1 the weight of oxide was 0.2250 g., and in sample 2 was 0.2255 g. The 10date standardization value was (). 2250 g. The Oxide in Sample l had a very slight yellow tinge, in Sample 2 Was almost pure White. The thiOSulfate filtrate S for each sample were evaporated to dryness after adding nitric acid, and the residues were taken up with 30 cc. of nitric acid and 250 cc. Of Water. A solution of 5 g. Of potassium 10date Was added With St, irring. The solution remained clear in both cases, even after standing over night, thus proving that the precipitation of thorium is COImplete . - º In determining the purity of the oxide, the following result was obtained: wt. of oxide taken was 0.1330 g. Wt. of oxide recovered was 0.1315 g. Loss was l. 5 mg. Purity was 99.65%. *- - - - - - - - - - - - - - - - - - - - - l. Meyer und Hauser, Loc. cit., 263. regard to completeness of precipitation and purity of the final oxide. No difficulty was experienced in filtering and washing the precipitate S. - - - . . .” Hydrogen Peroxide - - This method, as applied to monazite sand, was worked out by Benz' in 1902, and has been Widely published in text-books as a Short method. It has been subjected to much criticism in regard to the purity of the final oxide, this purity having never been deter- mined, however, by quantitative means, The completeness of precip- - it at iOn has not been que St. iOned. The method Was Carried Out, as directed by Benz, precipi- tating twice with hydrogen peroxide. The first precipitate had a yellowish-brown Color and the Second a light yellow tinge. Sample l gave 0.2239 g . of oxide, and Sample 2 gave 0.2311|| g. Both of these oxides had a light yellowish-pink tinge. The 10date standard- 1zation value was 0.2250 g. The following result was obtained for the purity of the oxide: Wt. of sample was 0.535 g.: oxide recover- ed., was 0.111136 g. ; loss was 9.9 mg. ; purity of oxide was 97.32 %. For a sand containing 5.5 % Thoa, the result would be about 0.12 % or 0.13 % above the correct result, assuming that the oxide alWays Imaintained this same purity. The 500 mg. Sample Chosen by Benz is too small, as the final Thoa weighed would be only about 27.5 mg. - - - - -------, --, Fumaric Acid - This method Was Originated by Metzger*in 1902. In testing the method, it was carried out exactly as recommended by the author, precipitating the thorium twice from a 10 % alcoholic solu- * * * * * * *- -s º -ºr sº - sº 1. Loc. cit. : Borelli, Gazz. chim. Ital, 39, [1]. H25 (1909). wºrn 2. J. Am. Chem. Soc. , 24, 901 (1902) tion. The thorium fumarate was somewhat difficult to f1lter. should not attempt to filter it without using suction. Sample 1 gave 0.1032 g. of oxide; Sample 2 gave 0.1016 g.: : . 'º. Sample 3 gave O. lol-2 E. : Sample H gave 0.1039 g. The 1odate stand- ardization value was 0.1049 g. The oxides were practically pure white. Purity of Oxide : Weight Of Sample Was O. 2675 g. oxide re- covered was O. 2660 e.: loss was 1.5 mg. purity of oxide was 99.1 m, a very men aegree or purity. The completeness of precipitation was tested upon a pure thorium nitrate SOlu t iOn . The amount taken contained approximately 100 mg. of thorium oxide. This was precipitated With runaric acid under the proper conditions. The filtrate gave no further precipi- tº at € with fumaric acid. It Was evaporated and tested With potassium iodate as previously described. The solution be Caiſle slightly but distinctly opalescent and on standing a slight precipitate settled to the bott OIn . This gave o.6 Iſlg . or mo., showing that the precipi- tation is very nearly complete. In experimenting with the filtrates from thorium ſumarate while analyzing the standard solution Of the sand, thorium could always be detected, but the amount was never more than O. 5 – O. 9 mg. - - It is probable that the method would give better results 1f a large sample were decomposed ana aliquot portions, equivalent t O ab Out, a 2 g. sample, Were analyzed. A possible source of loss is present, in the decomposit iOn Of the OXalate . In both the ſumäI'- iC and metanitrobenzoic acid methods, this is accomplished by the º º-º- º - - use Of potassium hydrº OX1Cle. If any Of the SOluble OXalate remains; * * * * * * * * * * *- *** * * * * * 1. In Sample i the reprecipit, at iOn Was Carried Out, as directed by Neigh in the Imodified Iſlet, an it, roben ZOic acid ſhe triod. 2, SOI. would result. The fumaric acid method was the first rea accurate published Iſle thod for this determination. Mêt, an it, roben ZOi C Acid - Two procedures are given by Neisn'ror the determination of thorium by the use of this acid. In the first method the rare earth oxalates are converted into hydroxides by potassium hydrox ide, the hydroxides are dissolved in nit, riC 3C id and evaporated tº dryness, the nitrates are dissolved in 500 to 600 cc. or water and precipitated at 60° to 80°with 150 to 250 cc. of metanitrobenzo- ic acid solution ( 3.5 to l; g. per 11ter). The solution is allowed t;O St. and < this temperature until the precipitate has all settled. The precipitate aſter washing i S aissolved in nitric acia, methyl Orange is added and then 25 C.C. Oſ metanitrobenzoic acid solution. The solution is neutralized with dilute annonium hydroxide until à pink tint, 1 S Obtained, then 50 CC. more Of the OrganiC. acid i S - added, the mixture is heated to 60° to 80° and the precipitate after standing is filtered, ignited and weighed, the final sation being With the blast laſſip . In applying thi S Iſle thod to monazite sana, some difficulty Was experienced by Neish and therefore the method was - modified. The modification consists in precipitating the nitric aC id SOLllt iOn Of the metanitrobenzoate With £50 t, a 3 Sillm hydroxide, Washing the hydroxides, dissolving them in nitric acid and evapor-- at ing to dryne SS. The residue is taken up With 600 cc. of Water and again precipitated with the Organi C acid. - In testing the method, the metanitrobenzoic àC1d WaS pre- pared in the following way. The Init, rat iOn product of benzoic acid W 3 S a1stilled with Steam tº O reſſioWe ben Zoic acid, di S SOLV ed in 2. Beilstein, Handbuch der morgani schen Chemie, 2, 1231; Mulder, Ann. 31, 297 (1840); Hubner, Ann. 222, 72 (1881). ºutnum- - ----------- ºuTulº - - - --- - - - - - - - - º 5 3Odium hydroxide and the sodium Salt purified by crystallizati This was converted into the acid, which, after thorough washing was dried. The melting point was 14.1°. - The modified Imethod Was used, in order to eliminate the necessity for experience. On dissolving the hydroxide, obtained by the action of potassium hydroxide up On the nitric acid solution of the first Inetanit, POben ZOate, in nitric acid, evaporating to dry- ness and taking up With Water, a Small residue was left which ala not, aissolve GVen On boiling. If this was filtered ort, the results were often too low, probably due to the failure to wash out all of the potassium salt of the organic acid from the hydroxide and thus causing 3. rew milligrams of the thorium salt to remain un- dissolved. If the precipitate was not filtered off, the results Were invariably Imuch t OO high, due to Silica. This trouble was avoided by dissolving the residue of nitrates in dilute nitric acid instead of water, filtering off the silica and repeating the evaporation. Any slight residue, remaining after agains water to the nitrates thus obtained, was not filtered but was allowed to become a part of the second metanitrobenzoate precipitate. Sample I gave 0.1036 g. of oxide; Sample 2 gave 0.1031 g.: Sample 3, gave 0.1031 g. The iodate standardization value was O.I.Olí9 g. The oxides were pure white. . . . . . . . . Purity Oſ oxide: weight of sample WaS (). 23.70 g. ; OXide recovered was 0.2860 g.: loss was 1 mg; purity of oxide was 99.65%. - - The completeness of precipitation was tested by experiment- - . ing w1th a sample Of pure thor illm. OXide. This Was ſused With potas- sium pyrosulfate and the melt dissolved in dilute nitric acid. The thorium Was precipitated by ammonium hydroxide, the hydroxide Washed and dissolved in nitric acid, the nitric acid solution was ,” evaporated to dryness and taken up with Water. A si g t residue was filtered off. The solution was diluted and precipitated with Inét an it, robenzoic acid and the precipitate Was filtered, washed and ignited as directed by Nelsh. The weight of the sample was O. lo'71 g . ; oxide recovered was o.1037 g . ; lo SS was 1.7 ms. The filtrate from the metanitrobenzoate was evaporated to dryness. The residue was taken up with dilute nitric acid and a solution of H. g. of potassium iodate was added. The solution became cloudy and on analysis gave 1. H mg. of Thoa. The filtrates from the thorium precipitates, obtained in the Work upon the standard solution or the sand, were also tested. The filtrate from the r1; precipitate was precipitated with potassium 1odate under the proper conditions Of acidity. The iOdate was di SSOlved in hydrochloric acid and Sulfur Ous aela; the hydroxide was then precipitated, aissolved in nitric acid and the iodate precipitation repeated. The filtrate from the second thorium precipitate was precipitated only once with potassium iodate. In the first filtrate 1.5 ng. of thorium oxide Were found ; in the second O. 9 Ing. These oxides were combined, dissolved by ſusion and the solution, strongly acid with hydro- chloric acid, was tested for thorium by sodium hypophosphate. A gOOd t e St, Was Obtained. - Thor” illſm metanitrobenzoate is very readily filtered. In that respect the method is preferable to the ſumāri C. acid Iſle thod. Neigh precipitate S his oxalates from a boiling solution. This procedure was criticized by Hauser and Wirth” in a discussion of Borelli's paper. They state that, in a hot solution, a notice- 1. Koss, Chem. Żtg., 36, 686 (1912). 2. Hauser und Wirth, Z. angeW. Chem. , 22, 1311 (1909). 3. Borelli, Gaz Z. Chim. ital. , 39 (l), 1125 (1909). able quantity of phosphate is carried down with the oxal º hä % s been the author's experience that on precipitating a dilute monazite sulfate solution with oxalic acid, either hot or cold, Washing the Oxalates until sulfate free and 1gniting them to oxides, a solution of these oxides will give at least a slight test for phosphate with ammonium molybdate. The precipitation of phosphate With the oxalate 1s a constant source of error in all of the methods requiring a preliminary precipitation with oxalic aCid. Lead Carbonate … . . . .” It should be mentioned that Giles' has proposed a method for the separation of thorium from the other rare earth elements by the use of a suspension of very pure lead carbonate. A process for purifying the lead carbonate is given. Thorium, Ceric Cerium and Zi rCOnium are precipitated while the other elements are not. The precipitate is aissolved, the lead removed by hydrogen sulfide, and the SOLult iOn Can then be precipitated by annonium hydroxide, or, if the separation is not complete, the lead carbonate precip- it at 1.On Can be repeat, ed. NO Specific directions are given f'Or, the application of this method to the analysis of monazite sana, and consequently the method was not investigated. º - º – º gº." is * . . . Potassium Iodate This method of Meyer and Speter? published in 1910, Was the first method in which the thorium 1 S Separated from the other earths by a direct precipitation from the Sulfuric acid solution - ºf - * º -- of the sand. As has been previously stated, their results were compared and agreed very closely with those obtained from the same sand by the laboratory of Dr. Gilbert of Hamburg, in Which 2. Meyer und Speter, Chem. Ztg., 34, 306 (1910). ºn laboratory the determinations for the German Thorium Syndicate are made. This is an excellent method and open to very little criticism. The expense of the reagent 1s recognized, but this is certainly Offset by the gain in Working time. The repeated trans- fer of the precipitate to a beaker and back to the same paper 1s somewhat objectionable, but is attended with very little chance for loss after one has become accustomed to the method. working º . º With solutions so strongly acid With nitric aC id 1s rather ll I'l- pleasant . - - " . The ract that the precipitation is complete is shown by the preliminary experiments upon the pure thorium oxide. Purity of the oxide: (1) Weight of sample was 0.2%; s: : oxide recovered was 0.21133 g . ; loss was 2.2 Ing. purity was 99.12 % (2)weight of sample was 0.2752 g. ;oxide recovered was 0.2738 g.: loss was 1.4 Ing. purity was 99.49 % (3) Weight of sample was 0.5082 g.: oxide recovered was 0.5057 g. ; loss was 2.5 mg. ; purity was 99.51 #. sepaeic acia. - This reagent Was proposed by Smith and James' in 1912 for the Separation of thorium from Other earthS. It S applicat, iOn t O the analysis of monazite sand was not suggested. It seemed Worth while to see if a complete separation of thorium from the other earths in the proportion in which they are present in the sand Can be effected in One precipitation. - 50 cc. Of a standard In Ona Zite SOlúlt iOn WáAtº precipit, at, ed by sebacle aC id as directed by the authors. The precipitate Was ignited to the Oxide, giving O. ll35 g. Oſ a partly White and * *-* -- * -- wºº “ - -ºº º ºs º- - - - - - - - -ss- partly brown oxide. The iodate standardization value *. ---. 0.1125 g. A reprecipitation would doubtless give an ent pure oxide. Ammonium Molybdate. This volumetric method was published in the form o thesis by Zons in 1911 and as a paper in the Journal of Industria Zons' in 1912. gº’ - -- : ºº & : and Engineering Chemistry by Metzger a A one gram sample of the sand is decomposed with ---, sulfur- ic acid, the sulfates dissolved in water and the rare earths precipitated as oxalates. These are transposed to hydroxides Whi Ch are di SS Olved in dilute nitric acid, evaporated to dryness and taken up with water. The solution is diluted to 300 cc., 20 - C.C. or glacial acet, 1C acid are added and one gram Of Sodium t acetate. A standard solution Of ammonium molybdate is now run in from a buret, about one-half C.C. at a time with stirring, until near the €110 point, and then dr Op by arov. The end point is aetermin ed by all OWing a drop Oſ the solution to cone in contact with a few drops of an alcoholic solution of diphenylcarbazide, soluble • - - . - -, -, 2- molybdates giving a pink color. -* - º, º " - º 'º - . For the preparation of the indicator, the method’adopt- ed by Metzger and Zons in their Journal article was used, con– N sisting of heating together phenylhydrazine and urea. The method of purification of the diphenylcarbazide was Slightly sº----------- *s---" " 1. J. Ind. Eng. Chem. , 1, 193 (1912). 2. Lecoq, J. Chem. Soc., 36, 369 (1901). 3. Skinner and Ruhemann, Ibid. , 53, 551 (1833 ). ſ) tº X. modified, in that instead of pouring the alcoholic into an excess of water, water was added, little by lit. , º, . the alcoholic solution until crystallization started. The tion of the indicator had stood for two weeks before be ºf . The molybdate and thorium nitrate solutions were of the sain * strength as those used by the authors. completeness or precipitation. Ammonium molybdate solution was added slowly with stirring to an amount of thorium nitrate solution equivalent to 50 Ing. Of thorium oxide, which had been diluted and treated with acetic acid and sodium acetate as recommended, until one or two ce. excess had been added. . . . . . . . . . * *:: The precipitate Was allowed to Settle and Was filtered. The º Fº, filtrate gave no precipitate with ammonium molybdate. It was evaporated to dryne SS and tested with potassium iodate ly described. Upon adding the iodate the solution became as previous- ;lightly º, 4. ºf gº ...tº . . . . Ing. Of Thoa recovered cloudy. Two samples gave 0.8 mg. and 0.6 ºr ºr . from the filtrates, showing that the precipitat lon, t least with arl eXC e SS Of ſmolybdate, i S präC ti Càily complete. ‘. Purity. Of the precipitate. The advisability of a ſl invest- igat iOn Of this point is apparent after reading the article by Metzger and Zons. In their work they first determined the amount of molybdate solution necessary to give the end point with a Of p thorium SOIut iOn . Other Paré earths, º º lanthanum, praseodymium, neodymium and gadoliniuſ, Certain amount namely cerium, were then added to the same amount of thorium solution and the t it ration Was repeat, ed. They ſound that Iſ..O.Pé iſ Olybdat, e SOil] t iOn Was required than When thorium was present, alone, this addition- º º al amount being approximately the same irrespective º º … or the concentration of the added element and indicating that the precipitate was quite impure. The amount of acid was th º increased from 1 ÇC. t. O 20 C.C. , the amount finally adop ed the titration was repeated upon thorium solutions containing lanthanun, praseodymium, neodymium and gadolinium, but in Of cerium, which is present in such a large anount in monazite and which is the most likely to precipitate with the thorium, was apparently not investigated under the final conditions of t titration. The tendency for cerium to go into the ceric condition renders it e Specially likely t O precipitate with the thorium. A. --- - Gerous hydroxide, on standing in the air, becomes partially oxidized to ceric hydroxide, this oxidation taking place quite rapidly; a cerous solution, on evaporation with nitric acid, tends to become partially oxidized to ceric nitrate? º In testing out the molybdate method, an in titration was first attempted. This consisted in adding a measui ed amount of molybdate solution to a standard thorium solution, º filtering the precipitate and precipitating the molybdate from the filtrate by adding from a buret a slight excess of a stand- ard solution of lead acetate, this excess being determined by º º *º- t it rating back With the ammonium molybdate SOlu t iOn , 11 Sing tannic acid as the indicator? An exact end point can be obtained in this way. The lead acetaté solution was standardized against … " - the molybdate solution. The cerium solutions used were cerous Chloride and Cer’Ous aſſimoniuſm nitrate. As either of these solutions; 2. Ibid., 30. * 3. 3Chindler, Z anal. Chem. , 27, 137 (1333). {} Would give a visible precipitat * … on boiling w purified before being us sodium thiosulfate, each sample was by boiling with sodium thiosulfate, filtering, adding sodium - . tº . . hydroxide to the filtrate, dissolving the washed hydroxide in dilute nitric acid and evaporating to dryness on a water bath It was round that cerium has a slight effect upon the ammonium molybdate titration of lead, the excess or molybdate required under the conditions of experiment was about 0.11 cc. This amount was always subtracted from the total molybdate used. - º 'º - . The all Ollnt, of thorium solution taken was equivalent to 61.2 of Thoa ; the amount of cerium solution was equivalent to 300 me. Of CeO2 . The average net, additional ſmolybdate required when cerium was present proved to be from 0. 5 to 0. 6 CC. This would be equivalent to 7 or 3 ne. of Thoa. The acidity and dilution Were in every case the same as recommended by the authors and the solution contained one gram of sodium acetate. The conditions º Were, however, not exactly the same as would be encountered in a direct titl’at, ion, as the time required in filtering and washing Was about two hours and more molybdate was added than was - necessary to combine with the thorium. Thorium molybdate is described by Metzger and Zons as a light yellow precipitate. In the eXperience Of the author, the precipitate is white except when mixed with cerium molybdate, in Whi Ch Case it has a yellow tint. It was described by º- onyaenius' in 1863 as a Whit, G ſiOC Cui Gnt, precipit, at €. The direct titration with molybdate, using diphenyl- carbazide as the indicator, Was also carried Out . The aſnount. Oſ thorillſ. SOlution taken Was equivalent to 6l. 2 Iſig Of Tnſ) 2. With --------- - - - - - - - l. Chem. Zentr, , 1363, 715. 3 º the thorium solution alone, the aver . . . - age of Sj X r from 1.02 cc. to H. lo ce. , was 1.06 cc. men an amoun o solution, purified as previously described and equivalent to 300 ne. Of CeO2 , was present, the average of eight results, was ing from 1.20 cc. t; O 1.33 ce. was 1.27 ce. The average additional molybdate required was 0.21 cc., which is equivalent to 3. l In of Thoa. The titrations were in all cases carried out as p as possible. The results on monazite sands, given by Metzger Zons, do not show a particularly high degree of accuracy, varying in one case between 1.35 % and 5.3 % Thoa and in another between ii. 30 % and 5.05% Thoa. - 3O(lillſ] Hypophosphate. This method was published by Rosenheim' in 1912. The thorium is precipitated directly from the sulfuric acid solution of the Sand by adding sodium hypophosphate (often called sodium subphosphate ). Obtaining this reagent Was at first, a Iſlätter Oſ SOIſle difficulty. It cannot be purchased. A number of methods for the sº º *...* * * * ... preparation Of hypophosphoric acid have been described. These may be divided into four Classes: the method of Salzerº improved *º- -e- - - - - - - - * *---- 1. Chem. zte. , 36, 821 (1912). 2. Ann., 137, 322 (1377); Ibid., 19, 28 (1878); Ibid., 211, 1 ; . ; ; (1882). 3 1. by Drawe' and by Banse: by the slow oxidation 1ow temperature and with 11mited access to the air. Philippº by the oxidation of phosphorus ty silver nitra e; tion of phosphorus by cupric nitrate; and the electrolyti Of Rosenheim and Pinkster* . . . . . . Rosenheim and Pinkster" s modification or Corne was the first one tried, as it should apparently give the best results when only small quantities Of the reagent are needed. The results obtained were, however, not very satisfactory, as the phos- phorus was not at all readily oxidized unless the cupric ni was heated and in that case the rapid oxidation produced chiefly Ordinary phosphOric acid. Bansa's modification or seizer's method was then tried. sticks Of phosphorus, which haa been immersed in water at dº - - - were bored through lengthwise with à sharpened knittins needle. A cord WaS passed through this hole and the stºck conia in this - way be suspended in an upright position. A number of stºcks or phosphorus were suspended in a large jar containine a 25% solu- tion. Of Sodiuſ acetate. the jar was covered with a heavy paste- board cover, the cords passes through this COVer and adjusted in - such a way that the top of the sticks were about 1 cm. above the surface, and the cover was raised just enough to give a very l, Ber. , 21, 3-ol (1888). 2, 2, anors, chem. , 6, 130 (1894). 3. Ber. , 16, 719 (1883); Sanger, Ann., 232, i (1885). H. J. Phar, chim, , [3], 6, 123. . 5, her, as, 2007 (1910). LOC cit . , 2005. * limited access to the air. s apparatus was º tº º . . . . - : 2 : room and, as the phosphorus oxidized away, º ...” º ---. *...* - . ". . . . . . . . . to present a new surface to the air. In a few days sodium ac º - . º . . . . .” . . . . . . . . hypophosphate began to crystallize. This method was a rairly gº - --~~~~ ~~~~~ - --~~~~ º --~ one. (A somewhat better modification was worked out. ****----...------...-. - , , -- ºr-------" " ers were made by cutting a 15 cm. test tube in two, blowing small hole in the bottom of the lower half and flanging the t The upper half of the test tube can easily be converted into the same form of container. These can be filled with phosphorus and #. - - º: ; * -- suspended in a sodium acetate solution by a cord tied around th neck of the container in such a way as to hold the container in a vertical position. It is best to keep the jar in cold water, thus Keeping the temperature COnStant, and avoiding bur ning of the phosphorus. When using these containers, the phosphorus does not - . . . . have to be in the form of large sticks. when suspended 1n sticks, they are likely t; O fu Se together above the surrace or the sol - - if they come in contact with each other; also pieces of phosphorus drop Ofſ into the solution as it tº oxidized away. ... --" º The Salt Was also prepared by the electrolytic method Of - Rosenheim and Pinkster! in which a plate of copper phosphide is used as the anode in an electrolyte consisting of dilute sulfuric - - º - - g acid. The phOSphOru S in the anode is OXidi Zed Chiefly to hypo- º phOS.phOr 1C acid. The copper is removed from the solution by electrolysis (using platinum electrodes), and the free acid is - . . . . . - - - ' ' " - half neutralized with sodium hydroxide or sodium carbonate and the acid sodium salt 1s separated by crystallization. The copper phosphide available was 1n the powdered form and, to convert it into a form suitable for an electrode, it was fused in a Meker ſurnace at about ll00°. The electrolytic method gave excellent arºe wºº' -- - sº sº sº mººr ºr sº see west essee rºe Sll it, S. It is Celºt, airly t, he best method for t large quantities or this reagent. The acid sodium salt was * … - º allized before being used. ** The hypophosphate method was carried out as º - º 50 g. sample of monazite sand was decomposed with 100 cc. or ~, - concentrated sulfuric acid at 250 and the sulfates were dissolved -- - º: - º ºf in water and diluted to one liter. AllOO ce. portion of this sol- 180 cc. of water. This º was heated to boiling and a saturated solution of sodium hypo- Ult iOn was treated With 50 ce. HCl (1.13) and --- º phosphate Was added With stirring until the precipitation was ºf 5 . . COImplete. After Set t ling, the precipit, at e was filtered and washed with water very slightly acidified with hydrochloric acid until the washings gave no precipitate or coloration with ammonium hydroxide and hydrogen peroxide. This was allowed to drain and - - ºf . put into a Kjeldahl flask. 50 cc. of concentrated sulfuric acid * . . . . -- º Were added and heat, ed to the boiling point. From time to time a º-º-º- . . º --- ºf . Small quantity Of potas Sium nitrate was added and the heating ; : * * * * * - º was continued until allmor the organic matter had been oxidized. This required one and three-quarters hours. The solution was transferred to a platinum dish and evaporated until Inost, Oſ the acid Was removed . water was adaea and aſſiſſCriuſ hydrº OXide and the solution was boiled. It was then acidified with just enough hydrochloric acid to dissolve the precipitate, and a slight residue was filtered off. The boiling Solut, 1 On Was treat, ed. With an eXC e SS Of oxalic acia and allowed to stand for 24 hours, and the oxalate --- * * -ºº º was then converted to oxide. Sample l Wt. Of oxide – O.2792 g. Th92 - 5.53 ¢. Purity of oxide: wt. of sample was 0.5428 g.: oxic * . recovered was 0.5319 g. ; loss was 10.3 ms. writy was 97.9% The filtrate fºr Om the thorium 1odate gave àI). excellent test for Cerium When ammonium hydroxide and hydrogen peroxide were added. It, Was evident in carrying out this method in the name described by Rosenheim that the solution in precipitating the oxalate was too strongly acia and that some of the thorium was remaining in the oxalate filtrate. The method was modified in such a way as to avoid this. The organic matter was destroyed by ammonium perchlorate, and the sulfate solution of the thorium hypophOSphate Was precipitated by boiling with an excess or s hydroxide, the hydroxide was filtered, washed, aissolved in about 5 cc. of hydrochloric acid and then allutea and precipitated by Oxalic acid. Sample lº 0.2848 g. – Wt. of oxide Thoa – 5. 70 %. Sample 2 wt. of oxide – 0.2926 g. Thoa – 5.35 %. Purity of oxide: wt. of sample was 0.5715 g.: oxide recovered was 0.5547 g.: loss was 16.3 mg. ; purity was 97.06 %. Rosenheim states that the OXalate , ſilt rate Will COntain the last traces of cerium, zirconium and titanium. While cerium oxalate is somewhat more soluble in acids than thorium oxalate, ion with oxalic acid ation of thor it? Iſ &W 6 of cerium. º º º solution, considerab cidity is º º If the a - wil: º: - - precipitated. It is to be noted that When precipitated, the - - º - --- - - º º º º oxide is lowered about 1 %. The oxides were all •º º or brown. º §OC. º The COImple tene º º has already been shown. ( i) 7t. of sample was O. 547 l. g. 0. 51423 g . ; loss Was H. 6 mg. ; purity was (2) Wt. of sample was O. 11760 g. ; oxide 2.2 mg. ; purity was (). HZ33 g . ; loss was - º º º - º º- º º º - ..º * for the separatiº n of º º º praseodymium, neodymium and other rare earth. ments, of sodium pyrophosphate, 1s given. the enoa is first tested upon standard solutions or rare earth suits and then upon three different samples Of monazite sand. The results upon iſion32, it e sand are compared with those obtained by the 1odate method. In this - . . . . . . ... - Way the result, S are indirectly compared with those obtained by the -º º º German Thorium syndicate. The results show a very close agreement. -: - º º º - º A new method for the oxidation of filter pâpér i S incorporated in- º t; O this method. - 2. The O t, he rº published methods for the determination of thorium in ſmona Zit; e Sand are investigated, especial at tent iOn being -- º paid to the completeness of precipitation and to the purity of º º the final OXide . º º 3. A method for determining the purity of thorium oxide is given. l!. The thiosulfate Imethod, When carried out in the prop- er manner, is entirely satisfactory. The oxide is pure and the precipit, at iOn 1 S complete. --- 5. The hydrogen peroxide method is unsat, isſact, Ory On account Of the iſſpurity Of the final OXi (16 . 6. The ſumāric acid method is ſairly satisfactory. The precipitäte is SOInêWhat diſfi Cult, t, O ſilt, ºr and Wash. Possible SOur Ce 3 Oſ Brºr Orº are di SCU S Sed. 7. In the Iſle tani trobenzoic acid method, provision must, be ſmade ſor the removal of Silica. The Oxide Obtained in this Iſlethod is plı re. The loss Of thorium is somewhat, excessive. 3. The potassium iodate method is st isfactory 9. One precipitation with sovacic acid does not sep thorium completely from the other rare earth elements in a so. t; iOn Oſ ſmOna Zit; e. - – º: - 10. In the molybdate method the precipitation of thorium is practically complete. The precipitate of thorium molybdate 1s contaminated with cerium. The results given by the authors do not show a reasonably close agreement. - - - ii. The methods for the preparation of sodium hypophos phate are discussed. A new modification of Bansa's method 1s given. - -. - lºº. - . - 12. The oxide obtained in the hypophosphate method is impure. There is a loss Of thorium due to too high acidity in the precipitation with oxalic acid. 13. The precipitation of thorium with sodium pyrophos- phate is complete. The oxide is sufficiently pure. ,-' American Chemical Society, If the following paper i 8 it is proposed to substitute the Of printed copies of the the accepted and published by the º nullilbe tº * - w - - - - * - - º - Si S º º ń º t # , , §§. A "... th published methods were tried, solubility of 1 ts salts is much the same as dymium and neodymium impart a cerium can be present without producing any color. Ew of THE METHOD FOR THE DE *º- THORIUM. ºf In the couse of the work upon the pyrophosphate method'. . . . . º º ſ’Orº the determination Oſ thorium in monazite sand, all of the * * * * * #. ... r. º. . . . . j-º-º: and it became evident that a thor- ject was advisable. - - ough investigation of the sub A high degree of accuracy is necessary in this determina– * -, tion. Meyer and Hauser “state this requirement to be that the result shall not vary from the correct number by more than 0.05 In some cases the methods do not fulfill this requirement. Thorium may be lost during the analysis, and the precipitate may contain e y to be ...º.º. º on account of 1: other rare earth elements. Cerium is especially likel present in the final precipitate become oxidized to the tetravalent state 3. -º'- º the solubility of the corresponding thorium salts. The color *of the final oxide is not an absolute criterion of its purity. Small quantitles of praseo- rº- strong color, while considerable It is recognized by good authorities"that a large sample of the sand, 20 - 50 g. or more, should be taken. Methods in 1. Carney and Campbell, This Journal, 36, 1134 (1911). 2. Meyer und Hauser, "Die Analyse der seltenen Erden und der Erd- săuren", page 259. 3. Hauser und Wirth, Z. angeW. Chem., 22, 1311 (1909). l!. Meyer und Hauser, LOC. Cit. , page 26(). Hauser und Wirth, Loc. cit. * the following work a comparison of the results obtain- ed by the different methods is made, the purity of the final oxide - º º - - º - is deter’ſſlined and also the COmpleteness of precipitation. The ide:3. - Was not; SO Iml] Ch t O COmpare a large number of results fºr On trie same Sand as to investigate the foundation of the method, that is, Whether the thorium is completely precipitated and the precipitate 11ncontaiſinated With Other rare earth S. Method 3 requiring the precipit, at iOn Of the rare earths as oxalates were carried out upon a standard solution or monazite - earths, thus insuring uniformity of sample. This solution Was Iſlade by precipitating a dilute sulfuric acid solution Oſ monazite Sand with an excess of Oxalic acid, Washing the oxalates several times by decantation, then transferring to a filter paper and Washing - - thoroughly With Water Very ſaintly acidiſied With hydrochloric acid. The Oxalate S Were then Converted to nitrates by oxidation With furning nitric âC id and finally 't O Chloride S by repeat, ed evaporat, iOn With hydrochloric acid. The dry ré Sicille of Chlorºi (i.es Was the ſh dissolved in Water, a SImāli amount Off insoluble Iſlatter filtered Of'ſ and the SOIllt, i Orl diluted. This SOil] tº 1 On WäS Stand- ardi Zed by the iOdiate method'. In every Case When this SOilt, i On was 11 Sed, the aliquot portion taken as a Sälſ, ple was ê Văp Orat, ed to dryness On a Wat, er bath in Order t O reſno Vê any possible trace of -hydrochloric acid. The chloride solution was used , rather than the nitrate, because of the statement of Meyer and Hauser” that Chloride solutions are preſerable to nitrate in the thiO sulfat, 6 ------------ l. Meyer und Speter, Cheſm. Zt g. , 3}, 306 ( 1910). 2. LOC. cit., page 263. * wº method. - - -: - º - - .. - - - The purity of the thorium oxide was determined in the -- º --- ſ’OliOWing manner. A sample was put into a weighed platinum Č rºll Ci- ble, ignited With 3 Mieker’ burner for twenty minutes and then Weighed. It was dissolved by fusion with potassium pyrosulfate and leaching out with dilute nitric acid. Any residue was filtered and ſºil Sed again until COIſ, pletely dissolved. The Solut, ion was pre- cipitated with ammonium hydrº OXide and the hydroxide was rintered and washed a few tº iſſle S With not W3 ter' . It, W33 dissolved in 30 CC. of concent rated nitric acid, diluted With Water, and the thor illuſ, was precipitated by adding a solution of 6 g. of potassium lodate. I The total Volume of the Solution Was about 300 cc. This was stir- | red repeat, edly and all OWed tº O St and Cold for about two hours. The 1odate was filtered and Washed a few times With the Washing sol- º ution used in the iOdate method. It was then dissolved in hydro- º Chiori C 3Cid With the additi On Oſ just enough sulfurous 3.Cid t O reduce all of the iodine to hydriodic acid, and the thorium Wä S precipitated from the boiling solution by ammonium hydroxide. The hydrº OXide Was washed thorùughly , dissolved in 6 cc. of hydro- chloric acid, diluted to 100 cc. and precipitated with 3rl 6 XC e SS Oſ’ OXaliC acid. The OXàlate Was filtered, Washed and ignited t, O OXide in the usual Imanner. In this Way the pure thorium OXi(ie present in the original sample was obtained. This Iſle thod, in- VOlving Only one precipitation as iodate, would not be $3 tº i Sí’āC“ tory for the Separat, iOn Of thorium from large quant, it ié 3 Of Other Pare earth eleſſlént S, but it is an eXCellent, Imethod ſolº the analy- Si S. Of Slight, ly impure oxides. To test, the method, Sample 3 Öſ thorium oxide from the pyrophosphate method Were fused With potassium pyrosiliſat, e and Subjected to purific at iOn by an i Odate precipitation as just described. The method was then applied the pure oxide thus obtained. In one sample 0.2498 g. was taken and 0.2493 g. recovered; in the second 0.4983 g. was taken and O. H934 g. recovered. - The methods are taken up in the order in which they wer published. The annonium oxalate method of Glaser's not consider- ed as it has been shown to be very inaccurate” the lead carbonate method of Giles*was not investigated as it aid not seen as promis- ing as the Other methods in which the rare earths are precipitat— ed as oxalates, on account of the difficulties in the purification of the lead carbonate, the removal of lead, etc. Sodium Thiosulfate. - * This method is due mainly to the work of Fresenius and Hintz" in 1896 and Hintz and weber‘in 1897. The authors do not apply the separation to the analysis or monazite sana, but it is well known that it has long been used for that purpose conflict- ing St. at eIſlent S have appeared concerning the completeness of pre- Cipitat 1.On Of thorium by sodium thiosulfate and the accuracy or the separation from the other rare earths. The precipitation has 3 S 3 1?Ulle been considered as incomplete, and the filtrate from the thorium thiosulfate has been precipitated by ammonium hydrox– ide, the hydroxides dissolved in ac1a, evaporated to dryness, - taken up With water, and the precipitation Pepeated in Order to 1. Chen, zig., 20, 612 (1896). 2. Hintz und Weber, Z. anal. Chem. , 36, 27 (1897); Drossbach, ... angew. Chem. , lik, 655 (1901); Benz, Ibid., 15, 297 (1902). Z. 3. Shem. News, 92, l and 30, (1905). , , , º, ... } @ 14. Z. anal. Chelū. , 35, 525 (1396) ſº-º- ºvº- - + . . A) nºw 5 º . LOC - C i t . ****** account of the exceedingly bad filtering properties of the large - *** hydroxide precipitate. Meyer and Hauser state that thorium 15 completely precipitated from a neutral chloride (not nitrate) º- 'º' solution 1f the solution 1s diluted and boiled for some time. The author is able to confirm this statement in regard to dilution *-ºs º - º - ºn-" " and boiling, but it seems doubtful if the nit, rate has any effect. Incompleteness of precipitation is probably due to the presence of acid and not to oxidation. Bolling destroys the thiosulfuric acid liberated and thus lowers the acidity. ". . . - . . . . . - ... The method’ was carried out as follows: 100 cc. of the standard monazite solution were evaporated to dryness on a water bath and the residue was dissolved in 250 cc. of water. This was heated to boiling and a boiling solution of 9 g, of sodium thio- sulfate was added. The resulting solution containing the precipi- tate was boiled for thirty minutes. It was then filtered and the precipitate washed. This was boiled with 100 cc. of hydrochloric acid (1 - 3) for about fifteen minutes, the solution was filtered and evaporated to dryness. The residue was taken up with 200 – 250 cc. of Water and precipitated just as before with a solution Of 5 g . Of Sodium thiosulfate. After r11tering and washing, t; he ----- precipitate was dissolved by boiling with 10 cc. of hydrochloric acid and 25 – 50 cc. of water. The residue of sulfur was filtered: ! / º the filtrate neutralized with amonia and then made acid with 5 CC. Of hydrochloric acia, it. was then diluted and precipitated With Oxalic acid. The oxalate, after standing, Was converted to oxide by ignition. 4, C, In Åample 1 the Weight Of Oxide Was O. 2250 g. and in | ~. - - & £º, gample 2 was O.2255 g. The iodate standardization value Was - - - - - - - - - - - - - l. Meyer und Hauser, LOC. cit., page 263. * Yºrk *N 0.2250 g. The oxide in Sample l had a very slight yellow tinge, in Sample 2 was almost pure White. The thiosulfate filtrates for each sample were evaporated to dryness after adding nitric acid, and the residues were taken up with 30 cc. of nitric acid and 250 cc. of water. A solution or 5 g. or potassium iodate was added with stirring. The solution - remained clear in both cases, even arter standing over night, thus proving that the precipitation of thorium iS complete. - * In determining the purity of the oxide, the following result was obtained: Wt. of oxide taken was o. 330 g. ; W t . Of oxide recovered Was O. 1315 g. ; loss was 1 - 5 Iſlg. , purity was 99.65%. - - The thiosulfate method is, therefore, satisfactory in regard to completeness of precipitation and purity of the final oxide. No difficulty was experienced in filtering and washing the precipitates. Hydrogen Peroxide. This method, as applied to monazite sand, was worked Out, by Benz" in 1902, and has been Widely published in textbooks as a short method. It has been Subjected to Imuch criticism in regard to the purity of the final oxide, this purity having never been determined, however, by quantitative means. The COIſlple tene SS Oſ precipitation has not been questioned. - The Iſlet, nod Was Carr’ i.ed out as directed by Benz, precipi– tat ing twice With hydrogen peroxide ( obtained by dilution of Fernyaroi). The fir, St. precipitate had a yell OWish-brown COlor and the Second a light yellow tinge. * * * * * * *-* *-* - nºw-- 1. Log. cit.; Borelli, Gazz. chim. ital. , 39, [1], 125 (1909). 33mple l gave o.2239 g of oxide and sample 2 O. 2311 g. Both Of the 36 oxides had a light yellowish-pink tange. The iodate standardization value was 0.2250 g. º - The following result was obtained for the purity of the oxide: wt. of sample was o. 1535 g. ; oxide recovered was o.º.36 2. 1OSS was 9.9 Ing. ; purity of oxide was 97.82 %. For a sand contain- ing 5.5% Thoa, the result would be about 0.12 % above the correct result, assuming that the oxide always maintained this same puri- ty. The 500 mg. sample chosen by Benz is much too small as the final thorium oxide Weighed Would be only about 27 mg. - - Furnari C. A C id. - This ſile thod Was originated by Metzger'ín 1902. In test, ing the method, it was carried Out exactly as recommended by the author, precipitating the thorium twice ſrolſ a l;0 % alcoholic solution. The thorium fumarate was somewhat difficult to filter. one should not attempt to filter 1 t without usine auction. Sample l gave 0.1032 g. Of oxideº Sample 2 gave 0.1016 g.: Sample 3 gave 0.1042 g. : Sample H gave O. i039 g. The iodate - standardization value was O. 101.9 g . The oxides were practically pure White. Purity of oxide: Wt. of sample was 0.267.5 g. ; oxide re- covered was 0.2660 g . ; loss was 1.5 mg. ; purity of oxide Was 99. Hiſ #, a satisfactory degree of purity. The COImplete IIe SS of precipit, at iOn Was tested upon a pure thorium nitrate solution. The amount taken contained approx– imately 100 mg. of thorium oxide. This was precipitated with 2. In Sample l the reprecipitation Was Carried Out as directed by Tjeish in the Imodified metani trobenzoic acid method, provision being Iſlade , h0W ever, ſor the removal Of Silica. • 3 fumaric acid under the proper conditions. The filtrate gave no further precipitat, e With fumaric acid. It was evaporated and test- ed with potassium iodate as previously described. The solution became slightly but di St, inct ly opelescent and On standing a Slight, precipitate settled to the bottom. This gave 0.6 ne. of tion, showing that the precipitation is very nearly complete. In exper- imenting with the filtrates from thorium runarate while analyzine the Standard solution Of" the sand, thorium could always be detect- ed, but the amount was never more than 0.5 Ing. - 0.9 mg. It i S probable that the method would give better results 1f a large sample were accomposed, and aliquot, portions, equiva- i.ent, t O at 1628 St, a 2 g. sample, were analyzed. A possible source Oſ’ i.OSS is present in the decomposition of the oxalate. In both the ſumariC and Inet anitrobenzoic acid Iſlethods, this 1s accomplish- ed by the use of potassium hydroxide. If any of the soluble oxal- ate remains in the hydroxide precipitate after washing, or if the transposition i S incomplete, a 10 SS Of thorium will result. The fumaric acid method was the first reasonably accurate published Inê thiOd for the determinat, iOn Of thorium in monazite sand. Metanitrobenzoic A Cid. TWO procedures are given by Neish' for the determination Of thorium by the use of this acid. In the first method the rare earth OXà late S are converted into hydroxide 3 by potassium hydrox– ide, the hydroxides are di SS Olved in nitric acid and evaporated to dryness, the nitrates are dissolved in 500 – 600 cc . . Of Water, and precipitated at 60 – 30 With 150 – 250 cc. of Iſetani trobenz— oic acid Solution ( 3.5 – 11 g. per liter). The solution is allowed to stand at this temperature until the precipitate has all - - - - - - -- w - - - * * * * 1. This Journal, 26, 780 (1901). **ºrra settled. The precipitate, after washing, is dissolve in nitric acid, methyl orange is added and then 25 cc. or metanitrobenzoic acid solution. The solution is neutralized with dilute ammonium hydroxide until a pink tint is obtained, then 50 cc. more of the organic acid is added, the mixture 1s heated to 60° to 80° and the precipitate, after standing, i S filtered, ignited and weigned, the final 1&nition being with the blast lamp. - In applying this method t O monazite sand, some airriculty was experienced by Nelsh and therefore the method was modified. The In OdiſiCat iOn Consist, S in precipitat ing the nitric acid S Oll]- tion of the metanitrobenzoate with p0 taS Sil]In hydroxide, washing the hydroxides, aissolving them in nitric acid and evaporating t, O dryness. The residue is taken up With 600 cc. Of Water and again precipitated with the organic acid. In test, ing the method, the metani trobenzoic acid was prepared in the following way'. Th9 nitration product or benzole âCid Was dist illed With Steam to remove benzoic acid, assolved in sodium hydroxide and the sodium salt purified by crystallization. Thi S was converted into the acid, which, after thorough Washing, Was dried. The melting point was llll . . The modified method was used, in order to eliminate the necessity ſor experience. On dissolving the hydroxide, obtained by the action of potassium hydroxide upon the nitric acid solution Of the ſir, St. metanitrobenzoate, in nitric acid, evaporating to dryne SS and taking up. With Water, a SImall residue Was left, Whi Ch did not dissolve even on boiling. If this was filtered off, the - * *-*-* = ** - - - - - - ess- 1. Hübner, Ann., 222, 72 ( 188!). -- Ol] t all Of the potassium salt of the organic acid f the hydrox– ide and thus causing a few milligrams of the thorium salt to re- main undissolved. If the precipitate Was not, filtered off, the results were invariably much too high, due to silica. This trouble was avoided by dissolving the residue of nit, räte S in allute nitric acid instead of water, filtering off the silica and repeating the evaporation. Any Slight residue, remaining arter agains water to the nitrates thus obtained, was not filtered but, was allowed to become a part of the second metanitrobenzoate precipitate. Sample l gave 0.1036 g. of oxide ; Sample 2 gave o.1031 g.: Sample 3 gave 0.1031 g. The iodate standardization value was - 0.1049 g. The oxides were pure white. * -- Purity Oſ oxide: wt. of sample was 0.2370 g.: oxide re- covered was 0.2860 g. ; loss was 1 mg. ; purity was 99.65 %. The COmple terle SS Of precipitat iOn Was tested by exper- imenting with a sample of pure thorium oxide. This was fused with potassium pyrosulfate and the melt dissolved in allute nitric acid. fine thorium Wà S precipitated by ammonium hydroxide, the hydroxide Was Washed and di SS Olved in nitric à Cid, the nitric acid solution W 3 S evaporated t O dryne SS and takerl, up With water. A slight resi– Cille WäS filtered Oſſ. The SOlution Was diluted and precipitated with metanitrobenzoic acid and the precipitate was filtered, washed and ignited as directed by Neish. The Weight of the sample was 0.1074 g. ; oxide recovered was 0.1057 g.: loss was 1.7 mg. The filtrate fºr OIn the Inetani troben ZOate Was evaporated to dryne S.S. The residue was taken up with dilute nitric acid and a solution of l; g. Of potassium iodate was added. The solution became cloudy and On analysis gave i. 1; Ing. Of thorium oxide. - The ſiltrates from the thorium precipitates, Obtained in 11 the work upon the standard solution of the sand, were also tested Trnē filtrate fºr OIſ, the first precipitate Was precipitated with potassium iodate under the proper conditions of acidity. The 10 date W 3 S dissolved 1n hydrochloric acid and sulfurous acid, the ---------- hydroxide Was the n precipitated, di SSOIV ed in nitric acid and the 1odate precipitation repeat, ed. The ſilt, rate from the second thorium precipitate was precipitated only once with potassium iodate. In the first filtrate 1.5 Ing, or thorium oxide We lºe round; in the Second O. 9 mg. The Se OXide S were combined, dissolved by fusion and the SOlút iOn , strongly acid With hydrochloric acia, was tested for thorium by SOdilum hypophosphate'. A good t; e St. was obtained. Thorium metamitrobenzoate is very readily filtered. III that, respect the Iſle thod 1s preferable to the runaric acid method. Neish precipitates the oxalates from a boiline solution. This procedure was criticised by Hauser and wirth” in a discussi Orl º 3 - - - Of Borelli's paper. They state that, , in a hot solution, a notice- able quantity Of prosphate is carried down with the oxalate. It häS been the author 's experience that On precipitating a dilute In Ona Zit; e SUlſat, € SOlu t iOn with Oxalic acid, either not or coia, Washing the OXalate S until sulfate free and ignit, ing them t O OXide S., a solution of these oxides will give at least a slight test, ſor phosphate. With ammonium molybdate. The precipitat, iOn Oſ phosphate. With the Oxalate is a constant source of error in all Of the Imethods requiring a preliminary precipitat iOn With OXàlic * - es- sº- * * *- ºr - ºn º - men -- * * * 2. LOC. cit. * waterºzºº" 3. LOC. C it . www.ºrworrºr wwww.rº 12 Potassium Iodate. This method of Meyer and speter'. published in 1910, was the first method in which the thorium is separated from the other earths by a direct precipitation from the sulfuric acid solution Of the sand. Their results were compared and agreed very closely with those obtained from the same sand by the laboratory of Dr. Gilbert, , Of Hamburg, in which laboratory the determinations for the German thorium industry ar'e made. This iS an excellent method and open to very little criticism. The expense of the reagent is recognized, but thi S is certainly Offset by the gain in working t iſne. The repeated transfer of the precipitate to a beaker and back to the same paper 1s somewhat objectionable, but is attended with very little chance ſor loss arter one has become accustomed to the method. - --- The fact that the precipitation is complete is shown by Meyer and Speter and is also shown by the preliminary experiments upon the pure thorium oxide. . - - Purity Of the Oxide : (1) Weight of sample was 0.2505 g. ; oxide recovered was 0.21483 g . ; loss Was 2.2 ha., writy was 99.12 %. ( 2) weight Of Sample Was 0.2752 g . ; OXide recoverea was 0.2738 g.: ; loss wa S 1.1 mg. : purity was 99. 19 %. (3) Weight of sample was 0.5082 2.; oxide recovered was 0.5057 g. ; loss was 2.5 mg. : purity was 99.51 %. sebacle Acid. This reagent was proposed by Smith and James‘in 1912 ſor the Separat iOn of thoriuſ ſpom Other earthS . It, S applicat, iOn 2. This JOurnal, 311, 231 ( 1912). to the analysis or monazite sand was not sugge worth while t; O Se G if a. complete separation or thorium other earths in the proportion in which they are present sand can be effected in one precipitation. . . . . . 50 cc. of a standard monazite solution were diluted 100 cc. and precipitated by sebacle acid as alrected by the authors. The precipitate was ignited to the oxide, giving 0. of a partly white and partly brown oxide. The 1odate standard- 1zation value was 0.1125 g. A reprecipitation would doubtless give an entirely pure oxide. - Ammonium Molybdate. This volumetric method was published in the form or a thesis by Zons in 1911 and as a paper in the Journal of Industrial and Engineering Chemistry by Metzger and Zons 1n 1912. A one gram sample of the sand 1s decomposed with sulfuric l— acid, the sulfates dissolved in water and the rare earths precip- itated as oxalates. These are transposed to hydroxides which are dissolved in dilute nitric acid, evaporated to dryness and taken up with water. The solution is diluted to 300 cc., 20 cc. of glacial ace t, iC acid are added and One eran of sodium acetate. A Standard SOillt, 1 On Of' aſſiſſionium Iſlolybdate is ſlow run in from a buret, about one-half co. at a time with stirring, l] Int, il neal’ the end point, and then drop by drop. The end point is determined by allowing a drop of the solution to come in contact with 3. f6, Wy drops of an alcoholic solution of diphenyl carbazide, soluble molybdates giving a pink color. ----------- - - - - - - l. J. Ind. Eng. Chem. , 11, 193 (1912). 2. Lecoq, J. Chem. Soc., 36, 369 (1901). 3. & the ſilë (, r) ()(i. adopted was used, consisting For the preparation of the indicato by Metzger and Zons in their Journal article of heating together phenylhydrazine and urea. The method of purification of the diphenylcarbazide was slightly modifica, in that instead of pouring the alcoholic S Olu t iOn into an excess of Water, water was added, little by little, to the alcoholic solº- tion until crystallization started. The solution of the indicator had stood for two weeks before being used. The molybdate and thorium nitrate solutions were of the same strength as those used by the authors . . . recipitation. Ammonium molybdate solu- -------- Completeness Of p. tion was added slowly with stirring to an amount or thorium nitrate solution equivalent to 50 mg. Of thorium Oxide, Which had been diluted and treated with acetic acid and sodium acetate - "S. as recommended, until ofte or twº ce. excess had been added. The (ſ. 27. - - ~~~...~" precipitate was allowed to settle and was filtered. The filtrate - - * : ---, gave no precipit, at e With ammonium ſmolybdate. It Was evaporated to dryness and tested with potassium iodate as previously Ciê šCrib – ed. Upon adding the iodate, the solution became slightly cloudy. Two samples gave O. 3 mg. and 0.6 mg. of Thoa rec OVG red ſr’Oiſ, the ſiltrates, showing that, the precipitat, iOn , at least with an excess Of molybdate, is practically complete. Purity of the precipitate. The advisability of an invest- igation Of this point is apparent after reading the article by Metzger and Zons. In their work they first determined the aſſ, Ourit, Of molybdate solution necessary to give the end point. With a certain amount Of pure thorium solution. Other rare earths, name— - - - - - - ºr mºm wº- - - - - l. Skinner and Ruhemann, J. Chem. Soc. , 53, 551 ( 1833). then added to the same amount of thoriu tion was repeated. They found that more molybdate solut required than when thorium was present alone, this additional amount being approximately the same irrespective of the nature titration was repeated upon thorium solutions containing lanthan- um, praseodymium, neodymium and gadolinium, but the errect or cerium, which is present in such a large amount in monazite and Which is the most likely to precipitate with the thorium, was - apparently not investigated under the final conditions of titra- tion. The tendency for cerium to go into the ceric condition renders it especially likely to precipitate With the thorium. Cerous hydroxide, on standing in the air, becomes partiall Oxidized to ceric hydroxide', this oxidation taking place quite Papidly , a cerous solution,on evaporation with nitric acid, tends to become partially Oxidized to Ceric nitrate? In test, ing Out the molybdate method, an indirect t it, I’ā— tion was first attempted. This consisted in adding a measured amount of molybdate solution to a standard thorium Solution, ſiltering the precipitate and precipitating the Inolybdate from º the filtrate by adding from a buret a slight excess of a standard solution of lead acetate, this excess being determined by titrat- ing back with the ammonium molybdate solution, using tannic acid as the indicator? An exact end point can be obtained in this . iſ ſever und Hauser, Loc. cit., 77. 2. Ibid. , 30. 3. Schindler, Z. anal. Chem. , 27, 137 ( 1333 ). way. The lead acetate solution was standardize molybdate solution. The cerium solutions used were cert and cerous ammonium nitrate. As either of these solutions wo give a visible precipitate on boiling with a sodium thiosulfat solution, each sample was purified before being used by boiling with sodium thiosulfate, filtering, adding sodium hydroxide to the filtrate, dissolving the washed yaroxide in allute nitric aCid and eV ap Orat. 1ng t O dryness On a Water bath. It was found that cerium has a slight errect upon the annonium molybdate titration of lead, the excess Of molybdate required under the conditions of experiment was about 0.11 cc. This amount was -. always subtracted from the total molybdate used. The amount or thorium solution taken was equivalent to 61.2 mg. of Tho... the amount, Of Cerillin solution Was equivalent to 300 ms. of Geo. The average net additional molybdate required when cerium was present proved to be from 0.5 to 0.6 ce. This would be equivalent to 7 or 3 Ing. Of ThD2. The acidity and dilution were in every Case the same as recommended by the authors and the solution contained one gram of sodium acetate. The conditions were, however, not exact, ly the Same as WOllld be encountered in a direct titration, as the time required in ſiltering and Washing was about two hours and more molybdate was added than was necessary to COmbine With the thorium. - Thorium molybdate is described by Metzger and Zons as a light yellow precipitate. In the experience of the author, the precipitate is White except when mixed with cerium molybdate, º - - in which Case it has a yellow tint . It was described by º º Chydenius' in 1863 as a white riocculent precipitate. The direct titration with molybdate, using alphony, carbazide as the indicator, was also carried out. The amount of thorium solution taken was equivalent, to 6l. 2 mg. of Thoa. ...” With the thorium solution alone, the average or six results, varying from 1.02 cc. to 1.10 cc., was 1.06 cc. When an amount . . . . ºf ºr - * ~ * ºf of cerous solution, purified as previously described and equiva- - lent to 300 mg. of CeO2, was present, the average of eight results varying from H. 20 CC. to 1.33 cc., was 1.27 ce. The average additional molybdate required was 0.21 cc., which is equivalent to 3. l Ing. of thos. The titrations were in all cases carried out as rapidly as possible. - - - The results on monazite sands, given by Met Zger and Zons, do not show a particularly high degree of accuracy, . varying in one case between 1.35 % and 5.3 # Thoa and in another - - between H. 80% and 5.05% Thoa. 1. Chem. Zentr, , 1363, 715. Sodium Hypophosphate. This method was published by Rosenheim' in 1912. thorium is precipitated directly from the sulfuric acid sol of the sand by adding Sodium hypophosphate (often called Sodium subphosphate ). - Obtaining this reagent was ſat first a matter of some difficulty. It cannot be purchased. A number or methods for the preparation of hypophosphoric acid have been described. These " ... * may be divided into four classes: the method or Salzer? ed by Drawe.” and by Bansa' by the Slow OXidat, 1 On Of" phosphorus improv- at a low temperature and with limited access to the air; the Iſlet, hod. Of Philipp; by the oxidation of phosphorus by Silver nitrate ; the method of corne: improved by RO Senheim and Pinkster? by the oxidation of phosphorus by Cupric nitrate ; and the electro- lytic method of Rosenheim and Pinkster? º Rosenheim and Pinkster's modification of Corne's method was the first one tried, as it should apparently give 1. Chem. Ztg., 36, 321 (1912). 2. Ann. , 137, 322 (1877); Ibid., 1914, 28 (1373); ibid. , 2.ll, l (1332); 3. Ber. , 21, 3401 ( 1333). H. Z anorg. Chem . , 6, 130 (1894). 5. Ber. , 16, 749 (1883); Sanger, Ann., 232, 1 ( 1335). 6. J. Phar. Onim. . [5], 6, 123. 7. Bër., H3, 2007 ( 1910). 3. Loc. º., 2005. Inê (3d6 (i. as the phosphorus was not at all readily oxidized unless the cupric nitrate Was heated and in that case the rapid oxidation produced chiefly ordinary phosphoric acid. Bansa's modification Of salzer's method was then tried. 3 ticks of phosphorus, Whi Ch had been immersed in Water at 10, Were bored through lengthWise With a sharpened knitting needle. A COI’d Was passed through this hole and the stick could in this Way be suspended in an llpright posit iOn . A number or sticks of phosphorus were suspended in a large jar containing à 25 % SOLllt iOn Of sodium acetate. The jar was covered with a heavy pasteboard COver , the cords passed through this cover and adjust– ed in such a way that the top of the sticks were about 1 on. alo OVG the surface, and the cover Was rail Sed just enough to give a very limited access to the air. This apparatus was placed in a cold room and, as the phosphorus was oxidized away, the sticks - were raised to present a new surface to the air. In a few days sodium aCid hypophOS phate began to crystallize. This Iſlethod Was à fairly good Orie. A SOIſleWhat better Inodification Was Worked Out . Small containers were made by cutting a lº CIn. test tube in two, blowing a SImall hole in the bottom of the lower half and ſlanging the t Op. The upper half of the test tube can easily be COnvert, ed int, O the same form of Container. These can be filled With phos— phorus and suspended in a sodium acetate solution by a cord tied around the neck of the container in such a Way as to hold the C Ontainer in a Vertical position. It is best to keep the jar in Cold Water, thus Keeping the temperature constant and avoiding burning Of the phosphorus. When using these containers, the phosphorus does not have to be in the form of la #º. suspended in sticks, they are likely to fuse togethe º surface of the solution if * * * they come in contact with each other also pieces of phosphorus drop off into the solution as 1 t is OXidi Zed a Way. The salt was also prepared by the electrolytic method of Rosenheim and Pinkster, in Which a plate of copper phosphide sº is used as the anode in an electrolyte nonsisting of dilute Sulſulº iC a Cid. The phosphorus in the anode 1s oxidized chiefly to hypophosphoric acid. The copper i S removed ſ rom the solution - by electrolysis, using a platinum anode, and the free acid 1s hair nellt, pali Zed With sodium hydroxide Or’ SOdilull carbonate and the acid sodium salt is separated by crystallization. The copper phOSphide available Was in the powdered ſorm; to convert it into a form suitable for an electrode, it was fused in a Meker furnace at about 1100°. The electrolytic Iſle thod gave eXCellent re Suit S. It is certainly the best method for the preparation of large - quant, it ièS Of this reagent. The aCid SOdillſ, Sãlt, WGS recrystal- lized before being used. The hypophosphate method Was Carried Out, as follow S : A 50 g. Sällple Of ſmOna Z1 t e Sand Was deCOſſipO Sed With 100 CC. Of (2Once Int, r" at €d Slli fºur i C acid at 250° and the sulfates were dissolved in Water and a11uted t; O one 11ter. Á 100 cc. portion of this solution was treated with 50 cc. of hydrochloric acid (l. 13) and l30 cc. or Water. This Was heat, ed to boiling and a Saturat, ed solution of sodium hypophosphate was added with stirring until the precipitation was complete. After settling, the precipitate was filtered and washed with Water very slightly acidified with hydrochloric acid until the Washings gave no precipitate ºf Ea: or coloration with ammonium hydroxide and h was allowed to drain and was put into a Kjeldahl flask. 50 cc. of concentrated sulfuric acid were added and heated to the boil- ing point. From time to time a small quantity or potassium nitrat was added and the heating was continued until all of the organic matter had been oxidized. This required about one and three- quarters hours. The solution was transferred to a platinum alsº and was evaporated until most of the acid was removed. water was added and ammonium hydroxide and the solution was boiled. It was then acidified with just enough hydrochloric acid to dissolve the precipitate, and a slight residue was filtered off. The boiling solution was treated with an excess of oxaire 3.Cid and WäS allowed to stand for 24 hours, and the oxalate was then converted to Oxide . MOna Zit; e D. Sample i. Wt. Of Oxide – O. 2792 g % Thoa - 5.53. Sample 2. Wt. of oxide – O. 2693 g. % Thoa – 5. H0. The average result for this sand by the iodate method was 5. H3 % Thoa and by the pyrophosphate method was 5.11 % Thoa. Purity of oxide: Wt. of sample was 0. 51123 g . ; Oxide recovered was 0.5319 g. ; loss was 10.9 mg. ; purity was 97.99 %. º The filtrate from the thorium iodate gave an excellent test ror cerium when ammonium hydroxide and hydrogen peroxide were added. It was evident in carrying out this Inethod in the manner described by Rosenheim that the solution from whic 1s precipitated was too strongly acid and that some of the thor1 was remaining in the oxalate filtrate. The method was modified in such a way as to avoid this. The organic matter was oxidized by sulfuric acid and ammonium perchlorate, and the sulfate solu- tion of the thorium hypophosphate was precipitated by boiling with an excess of sodium hydroxide; the hydroxide was filtered, washed, dissolved in about 5 CC. Of hydrochloric acid and Was then diluted and precipitated by oxalic acid. - The following samples were aliquot portions of the same solution used in the other two Samples. Monazite T). , Sample 3. Wt. Oſ oxide – O. 23113 g. - % Thoa - 5.70. Sample l; . Wt. Of OXide – O. 2926 g. % Thoa - 5.35. Purity of oxide: Wt. of sample was O. 5715 g. ; oxide recovered Was 0.55117 g . ; loss was le. 3 Ing. ; purity was 97.06 %. Rosenheim states that the oxalate filtrate will contain the last traces Of Cerium, Zirconium and titaniuſh. While cer illm OXalate is SOmeWhat more soluble in acids than thorium oxalate , a precipitation with oxalic acid in strongly acid solution is far from be in a good separation of thorium from cerium, even When the latter is present Only in SImall aſſolunt . If the acidity i S Imade high enough to hold Cerium in SOlution, COnsiderable anount S of thorium will also ſail to be precipitated. It is to be noted that When the acidity is lowered enough SO that all thorium is º nº ------- precipitated, the purity of the oxide is oxides were all tinged with pink or brown. 3Odil] In Pyrophosphate. - * , , . - In this method’, published in 1914, the thorium is precipi- tated directly from the sulfuric acid solution or the sana by - the addit, i.On Of SOdill Iſl pyrophosphate. In order tº O obtain a complete precipitation, it is necessary to boil the solution for five minutes after adding the reagent, in order to break up any soluble double pyrophosphate, or otherwise a few milligrams of thorium Will remain in Solution. The ré Sult, S checked closely with those Obtained by the iOdate method. The pyrophOSphate Iſlethod has been tested recently by ROSenheim and Triantaphyllides"and found satisfactory. The reagents used are inexpensive and the method i S rapid. - - - The COImplet, ene SS Of precipitat, iOI) is shown in the origin- al article by boiling the filtrate from the thorium pyrophosphate With SOdium hydrº OXide , no precipitate resulting. This filtrate al SO give S no i Odate Or hypophOSphate test for thor illm. The oxide was tested for cerium and none was found. Purity of Oxide : (l) Wt. Of sample was 0.517); g . ; oxide recovered was S 0. 5423 g . ; loss was 4.6 mg. ; purity was 99.16 %. (2) Wt. Of Sample was 0.11760 g. ; oxide recovered was O. H.733 g . ; loss Was 2.2 mg. ; purity was 99.5l. %. - - - - - - - - - - - - - l. Jººls Journal, 36, ll:34 (1914). 2. Ber. , 3, 592 (1915). Summary. ... The methods for the etermination of thoriuſ º monazite sand 3.12.6 investigates, especial attention being paid to the completeness Oſ precipitation and to the purity of the final oxide. 2. A method for determining the purity of thorium oxide i S given. - 3. The thiosulfate method, when carried out in the proper ſmanner, gives a pure OXide and a COmplete recovery of the thorium. l!. The hydrogen peroxide method is unsatisfactory on aCCOunt Of the iſnpurity Of the final Oxide. 5. In the ſurnaric acid method a practically complete precipitation is obtained. The precipitate 1s somewhat difficult to filter and wash. The oxide, 1s sufficiently pure. 6. Inn the metanitrobenzoic acid method provision must - - sº -g - - - be made for the removal of silica. The oxide obtained is pure. The iOSS Of thorium i S SOmeWhat eXCessive . 7. The potassium iodate method is satisfactory. 3. One precipitation With SebaC iC acid does not separate thorium COImpletely ſrºom the other rare earth elements in the proportion in which they are present in a solution of monazite. 9. In the molybdate method the precipitation of thorium z is practically COmplete. The precipitate Of thorium Imolybdate i 3 contaminated with cerium. The results given by the author's do not, ShOWſ a rea's Onably ClO Sé agreeſment, . 10. The OXide Obtained in the hypophosphate method is There is a loss of thorium due to too high acidity i º º - .." ecipitation of thorium with sodium pyrºphos- Univer Sity Of Michigan Ann Arbor, Mich. RULES COVERING USE OF MANUSCRIPT THESES IN THE UNIVERSITY OF MICHIGAN LIBRARY AND THE GRADUATE SCHOOL OFFICE Unpublished theses submitted for the doctor's degrees and deposited in the University of Michigan Library and in the Office of the Graduate School are open for inspection, but are to be used only with due regard to the rights of the authors. For this reason it is necessary to require that a manuscript thesis be read within the Library or the Office of the Graduate School. If the thesis is borrowed by another Library, the same rules should be observed by it. Bibliographical refer- ences may be noted, but passages may be copied only with the permission of the authors, and proper credit must be given in subsequent written or published work. Extensive copying or publication of the thesis in whole or in part must have the consent of the author as well as of the Dean of the Graduate School. 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