Alkali metal borates

In general, hydrated borates of heavy metals ate prepared by mixing aqueous solutions or suspensions of the metal oxides, sulfates, or halides and boric acid or alkali metal borates such as borax. The precipitates formed from basic solutions are often sparingly-soluble amorphous soHds having variable compositions. Crystalline products are generally obtained from slightly acidic solutions. 

The polyions postulated in solution all have known structural analogues in crystalline borate salts. Investigations of the Raman (66) and B nmr (67) spectra of borate solutions have confirmed the presence of three of these species the triborate (3), B303(0H) 4, tetraborate (4), [B405(0H)2 J, and pentaborate (5) Bb06(0H) 4, polyanions. Skeletal structures were assigned based on coincidences between the solution spectra and those solid borates for which definitive structural data are available (52). These same ions have been postulated to be present in alkali metal borate glasses as well. 

A number of reviews have appeared covering the various aspects of borate glasses. The structure, physical properties, thermochemistry, reactions, phase equilibria, and electrical properties of alkali borate melts and glasses have been presented (73). The application of x-ray diffraction, nmr, Raman scattering, ir spectroscopy, and esr to structural analysis is available (26). Phase-equilibrium diagrams for a large number of anhydrous borate systems are included in a compilation (145), and thermochemical data on the anhydrous alkali metal borates have been compiled (17). 

N. P. Nies, "Alkali-Metal Borates Physical and Chemical Properties," in Ref. 3, section A9, p. 343. 

Amorphous products were obtained in the reaction between alkali metal borates and cadmium chloride, analyzed as the 2 3 7 compound (337). More recently, a patent claiming the formation of 6CdO 7B203 (3-3.8)H20 has appeared (264). 

Tetraalkyl titanates react with organic borates, B(OR )3, to give complexes of the general formula Ti(OR)4 B(OR )3, which are useful as catalysts and cross-linking agents (562). Mixtures of chelated organic titanates such as TYZOR TE and TYZOR LA with alkali metal borates, such as borax, or boric acid can be used to produce shear-stable fracturing fluids (563). 

Pilot plant studies (flow rates, 1 cm/s) with the SB-1 anion exchange resin (column diameter, 0.3-0.7 cm) yielded distribution coefficients of the order D = 400 cmVg. The boron sorption process was shown to be film diffusion controlled. The equilibrium values of boron loading were reached in 6-8 hr [280]. Boron elution and resin regeneration were carried out with 0.1 M NaOH. The complete elution of boron required 10 column volumes at 10 BV and yielded concentrates of 100 mg/L. This facilitated the eventual reduction to solid concentrates of alkali metal borates [281]. 

A theoretical analysis has been made of the miscibility gaps in the alkali-metal borates, based on the concept of regular solutions. In each system the structural units which control the entropy of mixing are thought... 

Comparing results of molybdenum electro-deposition from several types of electrolytes, it was confirmed that the process is most successful in electrolytes consisting of a mixture of alkali metal fluorides and boron oxide (or alkali metal borate), to which molybdenum oxide or alkali metal molybdate is added as the electrochemical active component. 

In the binary glass-forming systems of alkali metal borates, it is possible to observe change in the trend of a number of physico-chemical properties in the concentration range of approximately 20 mole % of alkali metal oxide. This phenomenon is known in the literature as boric acid anomaly , and it is due to the change in the structure of the B2O3 melt caused by the alkali metal oxide addition and is related to the ability of boron to change its coordination number. 

Silicate, alumino-silicate, ferro- and ferri-silicate, calcium-titanium-silicate, and alkali metal borate systems were chosen. 

Table 3.3. Numbers of individual kinds of atoms in pure alkali metal borates...

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