A STUDY OF THE SOLUBILITIES OF YTTRIUM NITRATE AND YTTRIUM CHLORIDE IN WATER AT VARY ING TEMPERATURES MAURICE CROUSHORN CREW TMESIS FOR THE DEGREE OF BACHELOR OF SCIENCE CHEMISTRY" COLLEGE OF LIBERAL ARTS AND SCIENCES UNIVERSITY OF ILLINOIS 1921 . UNIVERSITY OF ILLINOIS THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION BY Maurice Croushorn Crew E N T I T LED _ _ A _ A _ _9 A _ ^ A ?_ _ _ S.9 1 uh 1 l_i tie s_ _ of _ Y t tr i um_ J_I it r a t _e_ _ a n d _ X tjtrium _ Ch lor ide_ _i n _ Wa t_e r a t_ _ Varying _ Te mp_e r_a tures IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS FOR THE DEGREE OF Bachelor of Science in Chemistry , College of Liberal Arts and Sciences, University of Iliinoie Approved Instructor in Charge HEAD OF DEPARTMENT OF ___ 500268 Digitized by the Internet Archive in 2015 https://archive.org/details/studyofsolubilitOOcrew Acknowledgement . The writer wishes to express his sincere appreciation to Dr. D. 3. Hopkins for suggesting the problem and the as- sistance furnished by him, and also to Dr. H.C.Kremers for his valuable sugges- tions in finishing the work and writing the thesis 1 ri rni^T.t^jcr7~.TV- ~.'vgrjQ rrr_^rzmM.' Table of Contents. page I. Introduction II. Description of Apparatus 3 a. The Constant Temperature Bath. h.The Dilatometer . c. The Crucibles. d. The Centrifuge. III. Purification of Materials 4 IV. Procedure.. 5 V. Calculation of Solubility. 8 VI. Solubility of Yt(P0 l 3)3 , 6Hg0 9 Data Curve 10 VII. Solubility of YtCln;*6H20 11 Data Curve 12 VIII. Discussion. 13 IX. Conclusions 13 X. Bibliography 15 J ro co a A STUDY OF THE SOLUBILITIES OF YTTRIUM NITRATE AND YTTRIUM CHLORIDE IN WATER AT VARYING TEMPERATURES . I. Introduction. Data for the solubility at different temperatures of most of the fare eath salts is lacking, principally because of the very limited amounts of these salts in a pure condition. Because of the possibility of utilizing such data in the preparation of more of these salts by fractional crystalisat ion the importance of deter- mining these solubilities is obvious. This problem is dependent upon first the preparation of the pure salt whose solubility is to be determined and second the meas- uring of the solubility of the salt in such a manner that it does not become contaminated and can be easily recovered. Fortunately, the University of Illinois has auanities of these R rare eath materials; that have teen in the process of purification for over twelve years, and it accordingly seemed feasible to under- take the present work. The ease with which yttrium nitrate and yttrium oxalate can be ignited to the oxide very much simplifies the analytical operations involved. The main nroblem then was the control of the thermostat and ob- 1 taining equilibrium in the solutions at the various temperatures. Description of Apparatus. Th6 Constant 'Temperature Bath . The ordinary thermostat provided with stirrer, heating units, cooling coils and regulator which could be set at any temperature from 14* to 95° was used. 2 The Dilatometer. This apparatus consists of a bulb and an attached capillary- tube and is very much like a large thermometer. The bulb and tube we re mounted upon a yard stick, which served as a scale. The Crucibles . Weighings of samples of soltition and of ignited salts were made in platinum crucibles contained in glass stopped weighing bot- tles. A constant counterpoise was used in all weighings. The Centrifuge . A high speed motor driven inclosed centrifuge was used in sep- arating the crystals prepared for use in the determinations, from their mother licuor. The centrifuge revolved two aluminum cups which contained the filtering devices. Each was fitted with a gooch' crucible which contained the crystals and a porceline crucible placed underneath which caught the filtrate. The Furnace : A small gas muffel furnace in which a temperature of 900* -950* was obtained, was used to ignite the salts. - • . . 4 Ill- Purification of Materials. Very pure yttrium oxalate taken from series P5 and prepared 3 by Hopkins and Balke was used. The latter was twice reprecipitated as the oxalate from pure water confining dilute acid. Yttrium nitrate . Th6 nitrate was prepared by disolving the oxide YtgOrr, which was obtained by igniting the oxalate, in strong HUO^. The solution was then evaporated until concentrated and the crystals obtained by cooling. The crystals were separated from their mother liquor in the centrifuge. A small circular peice of filter paper was placed in the bottom of the gooch crucible held in the centrifuge. The crystals with adhering mother liquor were packed with a rubber policeman into the gooch crucibles. After being run for two minutes in the centrifuce the porceline crucibles containing the mother li- quor we re emptied. The crystals were whirled again at high speed for three minutes and then washed with a drop of distilled water, and again whirled. After this the crystals were reerystalized from pure water, centrifuged as above and finally washed with ether. Three crops of crystals 7/ere taken from the acid mother liquor and then that remaining was diluted and precipitated as the oxalate. The crystals were pure white and like fine needles. Yttrium chloride . The chloride was prepared in exactly the same manner as the nitrate except hydrochloric acid was used to disolve the YtoO* in- stead of nitric acid. The crystals obtained were pure white and of define shape and size. Both the nitrate and chloride were kept, after drying in a va- . . cuum at room temperature^ in glass stopped bottles, kept within a dessicator. IV. Procedure . The solubility determinations were made upon solutions, which had been kept in contact with an excess of the crystals until satu- ration at a definitely known temperature. About fifteen grams ox the crystaline yttrium nitrate or yttrium chloride were placed in a dry erlenmeyer flask and to it five c.c. of distilled water added. 'The flask was then closed and placed within a thermostat, which had been regulated to the desired temperature. The small amount of water in contact with a fairly large amount of crystals made it unnecessary to stir the solution during saturation. The very small size of the sample made stirring almost impossible. The sample had to be small because of the small amount of material on hand, and its high solubility. After about five hours the solution was con- sidered saturated. One solution which was allowed to remain in con tact with the crystals for eight hours showed a solubility exactly the same as for one held only five hours. This indicated that five hours was long enough for the solution to reach equilibrium. At the end of the five houm two samples were removed from the flask for analysis. A cylindrical separatory funnel was used to withdraw the samples, because of the convenience of using the stopcock to hold the solution drawn up into its stem. A strainer made of fine silk of double thickness, prepared new each time, was held on the end of the stem by a small rubber band. This strainer served to retain the undissolved crystals which if drawn up with the sample would give high results. After drawing the sample into the 6 stem of the funnel the stopcock was turned, the stem withdrawn from the flask and the strainer removed. Then by turning the stopcock the sample was allowed to run partly into one crucible and partly into another. The yttrium salt in th6 samples was then determined: in cas6 of the nitrate by evaporating to dryness. igniting to the oxide (YtoOr-J and weighing; in the case of the chloride by diluting to about 700 c.c. precipitating from a hot solution with hot 10 % oxalic acid, filtering, igniting to the oxide and weighing. Precipitating the oxalate from a hot solution with dilute acid gave a very crystaline precipitate which filtered rapidly. The crucibles were kept within glass stoppered weighing bottles so as to prevent evaporation of the solution on the one hand and absorption of moisture and CO 2 from the air by the oxide on the other. By regulating the thermostat at different temperatures and re- peating the above procedure at each temperature considered, a series of points were obtained by which the solubility curves could be o plotted. The determinations at 0 C. were made by placing the flask in a large amount of ice placed inside a large Jar. In order to see if there were any temperatures between 25 G. and C. at which one or more molecules of water would separate from the hydrated salt a test was made with a dilatometer. About one gram of the crystaline salt was placed within the dilatometer tube and enough pure mineral oil added to fill the tube and rise slightly in the capilary tube when the ground glass stopper was pressed in. The apparatus was then mounted upon a yard stick which was used as a scale and submerged in the bath of the thermostat, ffc temperature was then slowly raise from room temperature to 95 *C. at regular temperature intervals the height of the~*^-yo-l column and the temperature were observed. The results are plotted l see figl-tfjJ If at some point a sharp break were found in this temperature-pres- sure curve it would indicate that some of the water had separated from the hydrated salt. One would expect, therefore, to find a 4 break in the solubility curve at that same temperature. Both the nitrate and chloride gave smooth curves indicating no change in the number of molecules of water held by the salt. Similarity, no breaks were found in the solubility curves of these salts by actual- ly measuring the solubility at a series of temperatures. Further it was thought that different results might be obtained by bringing a solution to equilibrium with its undissolved salt from below the temperature in question than in coming to equilibrium from above. In the case of the nitrate equilibrium was approached only from one side that is from below for those temperatures above and from above for those temperatures below room temperature, room temperature , a However, in the case of the chloride a series was run in which equilibrium was approached from below the temperature in question and another series in which equilibrium was approached from far above it. The points in the two series fell upon the same curve, this seemed to indicate that an equilibrium had been reached in both cases between the solution and the undissolved salt. E- qui librium was approached from above the temperature in question in the following manner; the flask containing the solution was gently heated to a point just below boiling until evaporation had taken place enough to cause some salt to crystalize from solution, this showed that the solution was saturated at that temperature. She temperature was then brought down to a given temperature and h6ld there in the thermostat for five hours. 1. 2. Dilatometer test with nitrate, Dilatometer test with chloride Temperature C, Heigh- of column Tempera- Height of co- of nujol in 8th ture G lumn in 8th of an inch. of an inch. 24.5 57 25.0 65 30. 62 35.5 76 . 5 36.5 68 45.5 87.5 42,0 74 55.5 98 , 5 48.7 81 67.5 111.0 55.5 87 76.0 121. . 65.4 97.5 85.0 132.0 23.6 106 90.0 138.0 77.5 1105 84,6 117 95.5 126 98. 127 H/gfaff-) of A/ts ya/ Co/vnnn /n e/ g/ifh'S //*?c/?e5 1 8 . V. Calculation of Solubility. The data taken at each determination was the weight of solution as sample and the weight of yttrium oxide (YtgOg) prepared from the salt in that solution. By multiplying the weight of the oxide by the factor 2Yt(U0^)rr - 2.43 the weight of anhydrous nitrate in Yt 2°3 solution is obtained or oy multiplying by 2YtCl^ - 1.73 the weight Yt 2 0g of chloride is obtained. The weight of the water actually dissol- ving that amount of salt is then found by subtracting the weight of salt from the weight of the solution. All results are expressed in grams of anhydrous salt dissolved in 100 grams of water. To get the result in this form, the following proportion was used: Wt . salt - n VJt. H p 0 100 where n = grams per 100 grams of water. / . 9 . Solubility of Yt( 1103)3 in 100 grans of v/ater. Temperature Wt . Solu- tion wt . oxide Wt. Yt( IIO^ Wt. HpQ Sol. per 100 ga. Hp.O 0 p 1.3073 .2596 .6308 .6770 93.1 22.5° CO C\J CM • 1 1 .2888 .7050 .5184 136. 1.2721 .2988 .7240 .5481 133 35° .7403 .1853 .4510 .2893 155 60.2° .5738 • 1561 .3804 .1934 197 .7974 .2193 .5350 • 2624 203.1 66.5 .9248 .2585 • 6280 .2968 211 Gr-ams p