IUPAC-NIST Solubility Data Series. 87. Rare Earth Metal Chlorides in Water and Aqueous Systems. Part 1. Scandium Group „Sc, Y, La… Tomasz Mioduskia… Institute of Nuclear Chemistry and Technology, Warsaw, Poland Cezary Gumińskib… Department of Chemistry, University of Warsaw, Warsaw, Poland Dewen Zengc… College of Chemistry and Chemical Engineering, Hunan University, Hunan, People’s Republic of China ͑Received 12 May 2008; revised manuscript received 20 May 2008; accepted 20 May 2008; published online 15 October 2008͒ This volume presents solubility data for rare earth metal chlorides in water and in ternary and quaternary aqueous systems. The material is divided into three parts: scan- dium group ͑Sc, Y, La͒, light lanthanide ͑Ce-Eu͒, and heavy lanthanide ͑Gd-Lu͒ chlo- rides; this part covers the scandium group. Compilations of all available experimental data are introduced for each rare earth metal chloride with a corresponding critical evalu- ation. Every such evaluation contains a tabulated collection of all solubility results in ͑ ͒ water, a scheme of the water-rich part of the equilibrium Y, La, Ln Cl3 –H2O phase diagram, solubility equation͑s͒, a selection of suggested solubility data, and a discussion of the multicomponent systems. Because the ternary and quaternary systems were almost never studied more than once, no critical evaluations or systematic comparisons of such data were possible. Only simple chlorides ͑no complexes͒ are treated as the input sub- stances in this work. The literature ͑including a thorough coverage of papers in Chinese and Russian͒ has been covered through the middle of 2007. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2956740͔ Key words: aqueous solution; lanthanum chloride; phase diagram; scandium chloride; solubility; yttrium chloride. CONTENTS 3.1. Critical Evaluation of the Solubility of YCl3 in Aqueous Solutions.............. 1773 3.2. Data for the YCl3 –H2O System.......... 1776 1. Preface.................................. 1766 3.3. YCl3–Inorganic Salt–H2O Systems. ...... 1781 ͑ ͒ 1.1. Scope of the Volume................... 1766 3.3.1. YCl3 –MCl–H2O M=H,K 1.2. Nature of the Equilibrium Solid Phases.... 1766 Systems........................ 1781 ͑ ͒ 1.3. Solubility as a Function of Temperature. 1767 3.3.2. YCl3 –MCl2 –H2O M=Mg,Cd 1.4. Quality of the Solubility Results. ........ 1767 Systems........................ 1784 ͑ 1.5. Solubility as a Function of REM Atomic 3.3.3. YCl3 –MCl3 –H2O M=La, Ce, Pr, Number. ........................... 1768 Nd, Eu, Gd, Ho͒ Systems......... 1785 1.6. Acknowledgments and History of the 3.3.4. YCl3 –YF3 –H2O System.......... 1789 Project.............................. 1768 3.4. YCl3–Organic Compound–H2O Systems... 1790 1.7. References for the Preface.............. 1769 3.5. Quaternary Systems................... 1792 2. Solubility of Scandium Chloride. ........... 1769 4. Solubility of Lanthanum Chloride. ........... 1794 2.1. Critical Evaluation of the Solubility of 4.1. Critical Evaluation of the Solubility of ScCl3 in Aqueous Solutions............. 1769 LaCl3 in Aqueous Solutions............. 1794 2.2. Data for ScCl3 in Aqueous Systems. ..... 1770 4.2. Data for the LaCl3 –H2O System......... 1803 3. Solubility of Yttrium Chloride............... 1773 4.3. LaCl3–Inorganic Salt–H2O Systems. ..... 1809 4.3.1. LaCl3 –MCl–H2O ͒ ͑ ͒ a Deceased. M=H,NH4 ,Li,Na,K,Rb,Cs ͒ b Electronic mail: [email protected]. Systems........................ 1809 ͒ c Electronic mail: dewenគ[email protected]. 4.3.2. LaCl3 –MCl2 –H2O © 2008 American Institute of Physics. 0047-2689/2008/37„4…/1765/89/$42.001765 J. Phys. Chem. Ref. Data, Vol. 37, No. 4, 2008 1766 MIODUSKI, GUMIŃSKI, AND ZENG ͑M=Mg,Ca,Sr,Ba,Cd͒ Systems. 1819 pounds ͑materials for glass and ceramic dyeing, lumines- 4.3.3. LaCl3 –MCl3 –H2O cence and laser technique, corrosion inhibition, hydrogen ͑M=Ce,Eu,Yb,Sm,Nd͒ Systems... 1822 storage, and nuclear fuel reprocessing͒. Also, organic chem- ͑ ͒ 4.3.4. LaCl3 –LaA3 –H2O A=F,Br,NO3 ists found a spectacularly high number of reactions catalyzed Systems........................ 1825 by REM chlorides. Potentially, medical chemists are looking 4.4. LaCl3–Organic Compound–H2O Systems.. 1827 to apply these compounds as imaging agents in computer 4.4.1. LaCl3–Amine hydrochloride–H2O tomography and the prevention of renal stones. Also, knowl- Systems........................ 1827 edge about the solubility in multicomponent systems as well 4.4.2. LaCl3–Hydrazine as the related equilibrium phase diagrams is essential for the hydrochloride–H2O Systems....... 1834 identification of complex compounds of REM chlorides with 4.4.3. LaCl3–Ketone–H2O Systems....... 1835 other salts and many organic compounds. This may likewise 4.4.4. LaCl3–Acetic acid–H2O System.... 1835 improve the extraction and refining of REM compounds. Re- 4.4.5. LaCl3–Amide–H2O Systems....... 1836 cently, several papers related to the solubilities of REM chlo- ͑ ͒ 4.4.6. LaCl3–Urea thiourea –H2O rides in binary, ternary, and quaternary aqueous systems have Systems........................ 1838 been published each year. Some selected solubility data of 4.4.7. LaCl3 –N-heterocycle–H2O REM chlorides in aqueous systems were previously Systems........................ 1841 collected,1–3 but no systematic evaluation of all relevant re- 4.4.8. LaCl3–Amino acids–H2O Systems. 1845 sults was carried out. This work attempts to systematize the 4.5. Quaternary Systems................... 1846 immense experimental material acquired in this field. We 5. Cumulative References..................... 1851 hope that the present volume will serve as a useful guide for research and technology that involves REMCl3. List of Tables This volume continues the evaluation series of solubilities of REM salts in water ͑nitrates,4 sulfates,5 ethylsulfates,6 7 8͒ 1. The experimental solubility data of ScCl3 in iodates, and other halides and REM halides in non- 9 water at two temperatures................... 1769 aqueous solvents. These projects have been connected with 2. Experimental values of solubility of YCl3 in activity of the IUPAC Solubility Data Commission and Sub- H2O as a function of temperature............ 1773 committee. This volume will be published in three parts: 3. Recommended ͑R͒, tentative ͑T͒, and doubtful Part 1 ͑this paper͒: Scandium group ͑Sc, Y, La͒ ͑ ͒ ͑ ͒ D solubilities of YCl3 in H2O at selected Part 2: Light lanthanides Ce–Eu temperatures............................. 1775 Part 3: Heavy lanthanides ͑Gd–Lu͒ 4. Experimental solubilities reported for the LaCl –H O system as a function of 3 2 1.2. Nature of the Equilibrium Solid Phases temperature.............................. 1796 5. Recommended ͑R͒, tentative ͑T͒, and doubtful Solubility and phase diagrams are mutually connected. ͑ ͒ D solubilities of LaCl3 in H2O at selected Phase diagrams aid in understanding and interpretation of the temperatures............................. 1800 solubility results, therefore their schematic sketches are in- cluded in every critical evaluation, except the ScCl3 –H2O List of Figures phase diagram because the corresponding data for this sys- tem are contradictory so far. It is common knowledge that 1. Selected solubility data for REMCl3, ordered the equilibrium solid phases in REMCl3 –H2O systems near according to atomic number of REM,at273 room temperature have constant hydrate numbers r of the ͑squares͒, 298 ͑circles͒, and 333 ͑triangles͒ K... 1768 chlorides: seven for La, Ce, and Pr and six for Sc, Y, and 2. Water-rich part of the YCl3 –H2O equilibrium Nd-Lu, as found by the method of Schreinemakers and phase diagram............................. 1774 chemical analysis and well confirmed by some crystallo- ¯ 3. Water-rich part of the LaCl3 –H2O equilibrium graphic studies. The isotypic heptahydrates are triclinic, P1 phase diagram............................. 1795 space group and isotypic hexahydrates are monoclinic, P2/n space group.3 The heptahydrate structure is based on the ͓ ͑ ͒ ͔+ 1. Preface nine-coordinate complex REMCl2 H2O 7 which forms dimeric ͓͑H O͒ REMCl REM͑H O͒ ͔4+ units. The hexahy- 1.1. Scope of the Volume 2 7 2 2 7 drate structure contains eight-coordinate species ͑ ͒ ͓ ͑ ͒ ͔+ A rather traditional generic term rare earth metal REM is REMCl2 H2O 6 . convenient for the title because it comprises the title ele- Below 273 K, the hydration number in REMCl3 ·rH2O ments: scandium, yttrium, lanthanum, and all lanthanides. may be, depending on the system, 8, 9, 10, or even 15, as Their chlorides seem to be the most common salts of REMs. established in exhaustive thermal analysis studies by In recent decades, we observe increasing applications of Sokolova.10 Unfortunately, only a monoclinic structure and these compounds in technology and science. They are used cell parameters for YbCl3 ·9H2O were identified by x-ray for the production of pure REMs, their alloys, and other com- diffraction. Therefore, it would be very useful to confirm the J. Phys. Chem. Ref. Data, Vol. 37, No. 4, 2008 IUPAC-NIST SOLUBILITY DATA SERIES. 87 1767 results of Sokolova in another laboratory. At temperatures be used only in very narrow temperature ranges. Therefore, higher than 380 K the isotypic REMCl3 ·3H2O hydrates may we tried to use the advanced form of the solubility equation, be formed, and they were structurally investigated by Reuter applied for salts within the IUPAC solubility evaluation et al.11 who found orthorhombic structure, Pnma space projects,15 to describe more adequately the liquidus: group. The structure consists of ͓REMCl / Cl͑H O͒ ͔ chains, ␯ ␯ ͑␯ ͒ 4 2 2 3 ln͕x ͑1−x͒r͑␯ + r͒ +rr−r͓1+͑␯ −1͒x͔− +r ͖ where two REM3+ ions are connected via two Cl− ions. A comparison of the phase diagram shapes of the water- = A + BT−1 + C ln T + DT, ͑3͒ rich parts of the REMCl –H O systems showed quite 3 2 where ␯ is the number of ions produced upon salt dissocia- smooth changes in their invariant points and temperature tion and r is the number of water molecules in the equilib- ranges of stability of the equilibrium solid phases through the rium solid phase.