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The physicochemical properties of C 4 3C 8 carboxylic acids (mutual solubility of carboxylic acids and water, ionization constants in water, distribution between water and 1,2,4-trimethylbenzene, dimerization constants in 1,2,4-trimethylbenzene) were studied. Since indium carboxylates are sparingly soluble in 1,2,4-trimethylbenzene and the second organic phase is formed in the system, In-containing scintillators can be prepared from C 4 3C 5 acids only in the presence of neutral organophosphorus compounds. The best results were obtained with an extracting agent containing isovaleric acid (C 5 ) and 0.25 M triisoamylphosphine oxide.The scintillator prepared in this system contained 80 g l !1 In and had a transparency of up to 2 m and a 40% light output. These parameters did not change when the sample was stored in tightly sealed dark glass vessels for 2 years at 12334oC in an argon atmosphere. Acids C 6 3C 8 can be used for In extraction without organophosphorus additives. The best results were obtained with methylvaleric acid (H 2 MVA, C 6 ). The correlation between the transparency and light output of the scintillators, on the one hand, and the preparation conditions, on the other hand, was studied. The properties of scintillators prepared from solutions of polymeric indium hydroxy-2-methylvalerates in 1,2,4-trimethylbenzene {[In(2MVA) 0.8 (OH) 2.2 ] n (n = 93115)} were the best. A procedure for extracting indium hydroxycarboxylates and preparing scintillators suitable for LENS experiment was developed. Scintillators with a volume of 4 l, an In concentration of 50 g l !1 , a light output more than 65%, and a 3-m transparency were prepared. Preparation of efficient low-energy neutrino detectors is one of the main problems of modern physics and astrophysics. Liquid organic scintillators (LOSs) allowing preparation of detectors with a large volume and arbitrary shape are usually used for this purpose. Foreign impurities, primarily natural radioactive elements U, Th, Ra, 40 K, etc., can be readily removed from these scintillators. To detect neutrinos efficiently, elements interacting with neutrinos or with particles formed in neutrino reactions (usually neutrons) are introduced into LOSs. These additives can deteriorate the scintillation parameters of the detectors (light output and transparency for optical radiation) and can decrease the stability of these parameters in time.Since the experiments on neutrino detection last from several months to several years, the detector properties should not substantially change within this time.High-energy neutrinos were successfully detected in experiments with solar neutrinos [1] and reactor antineutrinos [2,3]. To increase the sensitivity of these experiments and to detect low-energy neutrinos, elements having high cross section of reactions with neutrinos (ytterbium, indium, and gadolinium) should be introduced into the scintillator. Indium is the most suitable additive for studying solar neutrinos, and gadolinium is the best for antineutrinos formed in nuclear reactors. Th...

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The main features of extraction of Sc from aqueous nitric acid solutions with triisoamyl phosphate (TIAP) were studied. It was shown that Sc passes into the organic phase in the form of Sc(NO 3 ) 3 . 3TIAP. The extraction isotherms of Sc from its aqueous HNO 3 solutions and from those containing salting-out agents (LiNO 3 , NH 4 NO 3 ) with TIAP in dodecane were obtained. The distribution factor of Sc was studied in relation to the concentrations of TIAP, salting-out agent, and HNO 3 . The extraction of Sc and impurity metals (Zr, Th, REE) with TIAP was studied at widely varied HNO 3 concentration in the aqueous phase. The separation factors of Sc from impurity metals were determined. Scandium, a rare metal, finds application in various modern branches of science and industry. However, high price of scandium caused by complicated technique of its recovery from very lean ores hinders wide-scale application of this metal. Therefore, the development of techniques ensuring the efficient recovery and purification of this metal is an urgent problem.It is known that the main industrial process for recovery of rare metals, among them scandium, is extraction. This technique is characterized by high performance, relative simplicity of equipment and process control, high selectivity, and other advantages.As a rule, rare metals are extracted with neutral organophosphorus compounds (mainly TBP) and organophosphorus acids, e.g., di(2-ethylhexyl) hydrogen phosphate (HDEHP).A new organophosphorus reagent, triisoamyl phosphate (TIAP), recently became available. It was reported [1, 2] that, in extraction of REEs and other metals, this extractant shows certain advantages.TIAP in inert solvents ensures higher stability of the organic extract with respect to its separation into two organic phases in recovery of metals and acids from their concentrated aqueous solutions. The solubility of TIAP in water is approximately twenty times lower than that of TBP. Low solubility of TIAP in water is especially important in preparing high-purity scandium and other metals, since it decreases the contamination of raffinate with phosphorus and facilitates the regeneration of solutions to be discharged and evaporated.No data have been reported on extraction of Sc and impurity metals with TIAP. In this work we studied these questions to estimate the suitability of TIAP for extractive recovery and purification of scandium to obtain high-purity metal. EXPERIMENTALIn our experiments we used commercial triisoamyl phosphate, TU (Technical Specification) 6-02-13-203 83. This reagent contained more than 98% main compound, 0.06% isoamyl alcohol, and less than 0.002% isoamyl hydrogen phosphate. The density of this reagent was 0.952 g cm !3 . Before extraction, TIAP was triply treated with aqueous Na 2 CO 3 and then washed with distilled water to neutral reaction. Dodecane (pure grade) was used as diluent.The Sc-containing salt solutions were prepared by dissolving scandium oxide (99.9% purity) in the required amount of aqueous mineral acid. The mineral acids ...