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...
