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WI WUHWINWINWNWNH 136 047 THS THE E’REPARATEQN AME? FRGEJERETES OF SOME SCANE‘JEUM CGfiAPQUflQS Thués far fire flowed; cf ML D. MICHEGAR SKATE CGLLEGE Road Fan‘s? Eéfiey W54? ', A" V «I V uni-1 numb-.- a:-—....-< . This is to certify that the thesis entitled The Preparation and Properties of Some Scandium Compounds presented bg heed Farrar Riley has been accepted towards fulfillment of the requirements for _P_hs_21_ degree in W Major prof ssor [7)3te Agril 22 , 1251+ LIBRARY Michigan State University PIACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 6/0I chlFIC/DateDue.p6&p.15 THE PREPARATION AND PROPERTIES OF SOME SCANDIUM COMPOUNDS BY REED FARRAR RILEY A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Chemistry 1954 ACKNOWLEDGMENT The author wishes to express his gratitude to Professor L. L. Quill, for his considerate and able guidance of this work, and to Marjorie Riley for her patience and aid. ******* ***** ##1‘ * vr Lx I \-I I_\ 4—\ \_I \.I TABLE OF CONTENTS I. Introduction ............................. 1 II. Historical .............................. 2. III. Experimental ........ ................... 5 A. Oxalates ............................... 6 B. Fluorides ............................. 25 C. Trichloroacetates, Acetates and Carbonates .................... 35 Oxides, Hydroxides and Sulfates.. ....... 41 Polarographic Studies of Solutions Containing Scandium Salts ....... 48 IV. Summary ............................... 59 V. Bibliography ........................... 61 I. Introduction Since the discovery of scandium in the latter portion of the nineteenth century, work on this element has been both sporadic and limited, although, according to V. M. Goldschmidt, scandium "occurs in the earth's crust to at least five parts per million, so that it is as common as arsenic, and nearly twice as common as boron". This neglect has probably two reasons: little commercial use at the present and scarcity of known scandium ores. Too, since scandium has traditionally been included with the rare earths, chemists may have felt the same reserve in working with scandium. However, as the lightest transition element and the bridge both between groups III and IV and between aluminum and yttrium within group III, it should invoke modern chemical interest. The purpose of this thesis then shall be not only to present material gathered as isolated facts, but to correlate them within the framework of group 111. Since the scandium literature has been so well reviewed recently (53) , the organization of this thesis is a little different from the usual. In the section entitled "Historical" the development of scandium chemistry and the relation of scandium to surrounding elements is reviewed in broad contour. The experimental section is divided into five subsections, each dealing with a separate phase of scandium chemistry. Every subsection is preceded by an analysis of pertinent work in that particular field, followed by the experimental work in this study. The last section sums up work herein completed. II. Historical The discovery of scandium in 1879 (45) by Nilson, who recognized it as ekaboron, provided more credence to Mendeleef's periodic arrange- ment of the elements. Much of the early work was done by Nilson and Cleve. The compounds that scandium forms with a large number of anions, both simple and complex, were investigated around the turn of the century by Crookes. About 1910 much work, including solubilities and conduc- tivities, was done on the simple oxalates and sulfates by Meyer _et_a_l. and Wirth. The formation of double sulfates and oxalates with group I and group I-like ions was also investigated. Later Sarkar and Urbain prepared more double scandium compounds with different anions, and commented too, as did the earlier authors,on the striking difference in basicity between it and the rare earths. The most modern and still extensive studies on scandium were made by the Sterba-Bbhms, who, among other things, studied simple and double oxalates and carbonates, the formates and acetates. More recent studies on the structure of scandium compounds, spot tests, etc. , have been made more for rounding out a series of measurements than for elucidating the chemistry of scandium. The two characteristics, then, which loom large in any discussion of scandium are its weakly basic character and its tendency to form double salts. These are just the properties which have allowed it to be unjustly classified with the lanthanides and yttrium, because in the rare earth series, double salt formation is prevalent, and the yttrium group elements have distinctly more acidic properties. A number of researchers have pointed out that scandium differs from the rare earths (59, 67, 73, 74). Sarkar (59), in a rather complete comparison of the rare earths and scandium, \J’ -3- has detailed these differences. If their fluorides are compared, one sees, first of all, that scandium fluoride is insoluble in hydrochloric acid, whereas, in the same medium the rare earth element fluorides are relatively soluble . As a matter of fact, their solubility increases, in the cerium group at least, with decreasing basicity (increasing atomic weight) (41). More striking than the latter is the large solubility of scandium fluoride in excess of ammonium fluoride and the formation of well defined complex fluorides with ammonium and alkali metal ions (41, 65). The acetylacetonates of the rare earths are not volatile as is scandium acetylacetonate. Further, the latter exists in organic solvents as a monomer, while the rare earth acetylacetonates may be dimeric in the same media. With respect to the rigorous isomorphism found in the compounds of the rare earths, one finds no scandium salt isomorphous with the analogous rare earth compound. Covalent and ionic compounds of scandium are isomorphous with analogous compounds of Fe(III), C0(III), Cr(III), Al(III) and often Ga(III), In(III) and V(III). (59) If we turn next to the carbonates, we find well developed normal salts for rare earth ions whose ionic radii areas small as yttrium (27). To the contrary, scandium probably does not form either a normal carbonate or basic carbonate (68). Scandium sulfate is a very soluble compound and hence is different from the slightly soluble rare earth sulfates. The temperature coefficient of solubility of the scandium compound is positive, whereas, for the rare earth sulfates, the coefficients are negative. The double sulfate of scandium I -4- being water insoluble (59) reminds one of the cerium group, but placement here is ruled out on the basis of ion size. With the exception of ceric oxide, rare earth oxides dissolve comparatively easily in mineral acids, but scandium oxide is more refractory and solution takes place slowly even in boiling, concentrated acids. Lastly, one may mention some solubility anomalies. Scandium oxalate is slightly soluble in neutral and dilute acid solutions while the rare earth oxalates are known to be quantitatively insoluble under these conditions (64, 84). Recent studies have shown that the high solubility of scandium chloride in HCl-saturated: water, ethyl alcohol-water, and ether-water mixtures permits a separation of scandium from aluminum, yttrium and the lanthanides whose chlorides are insoluble in these media (I). The similarity of the properties of scandium and aluminum is more striking than is generally pointed out. The fact that aluminum also forms an acetylacetonate, covalent enough to be distilled and monomeric in organic solvents, should be mentioned (62). Aluminum oxide, like scandium oxide, is quite refractory towards mineral acids. The isomorphism of their compounds has already been stated. In addition, Weiser and Milligan (77) have pointed out the similarity between the structure of Y-AlOCOH and hydrated scandium oxide. The similarity of their fluoride complexes is another consideration. However, it is puzzling that the strong amphoterism of aluminum hydroxide does not appear with scandium hydroxide. Aluminum carbonate has never been isolated, analogous to the behavior of scandium (4). Too, aluminum sulfate is soluble although strongly hydrolyzed. As a last point, one may point out the formal analogy presented -5- by the compositions of Sc c and A14C3 (20, 62). 4 3 In some ways one may think of scandium as a bridging element between the third and the fourth periodic groups. The analogies, naturally, are not as numerous as within group III, but some are: Zirconium and scandium sulfates are soluble; zirconium, thorium and scandium form many basic and double salts; thorium and scandium fluorides are insoluble in HCl (62). Again, thorium forms an 8-quinolinolate with one molecule of 8-quinolinol of solvation (17) as does scandium oxinate (54). Wirth reports that the low solubility of scandium oxalate in concentrated sulfuric acid solutions (4. 32 N) is more like thorium oxalate than analogous rare earth compounds (84). III. Experimental The scandium used in this study was part of the stock at Michigan State College. It was known to be free of all metals except a small (l-3%) amount of calcium, which was removed by precipitating the mixture with ammonium fluoride and then leaching out the scandium with excess of ammonium fluoride. Under these conditions, scandium fluoride forms a soluble complex fluoride while the calcium salt remains unchanged. The double fluoride solution was filtered, evaporated to dryness in platinum dishes, and the fluorides converted to sulfates by evaporation with concentrated sulfuric acid. The ammonium sulfate was then volatilized and the residue dissolved in boiling water, precipitated as oxalate and converted to oxide by ignition at 850°. Because of the scarcity of scandium all residues were carefully saved and regularly recovered. The qualitative test using conchineal (53) was a great help in determining whether solutions contained a worth while amount.

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