Borax structure

Fig. 19. Borax structure, where x = 8 for borax decahydrate and x = 2.67 for borax pentahydrate...

Methyl borate Section of borax structure Pyroborate ion... 

The MejSi protecting groups in 58 a and 59 a could be removed by treatment with sodium tetraborate (borax) in MeOH/THF, yielding 58c and 59 c, respectively, as very unstable compounds [84]. Any attempts to obtain characterizable two-dimensional all-carbon network structures [3,4] by oxidative polymerization of 59 c have failed. 

Most borax is produced from tincal (native borax) ore in a process that amounts to a large scale continuous recrystallization. Borax pentahydrate crystallizes in the Na20-B203-H20 system at appropriate concentrations above 67 °C. It contains two crystallographically unique 6-coordinate Na" positions and three unique water positions. A more recent refinement of its structure shows that one of these water positions is not fully occupied, giving an actual composition of Na2[B40s(0H)4] 2.67 H2O [86]. 

Kernite (Na2[B40s(0H)2] 3 H2O = Na20 2 B2O3 4 H2O) is also an important industrial mineral that is mainly used to produce refined borates, boric acid and borax. The polymeric borate structure of the kernite is shown in Fig. 7b above. Upon hydration, kernite converts to the monomeric borate tincal, which dissolves more readily. Thus, kernite may be hydrated to facilitate processing into borax. Although primarily a raw material for the manufacture of refined borates, concentrates of this mineral have been used as industrial products. 

ILs have been used in the CE-electrochemiluminescence (ECL) method to determine bioactive constituents in Chinese traditional medicine [58]. CE/Tris(2,2-bipyridyl) ruthenium(II) (Ru(bpy)3 +) ECL, CE-ECL, with an IL detection system was established to determine bioactive constituents in Chinese traditional medicine opium poppy, which contains large amounts of coexistent substances. Running buffer containing 25 mM borax-8 mM [C2CiIm][BF4] (pH 9.18) was used, which resulted in significant changes in separation selectivity and obvious enhancement in ECL intensities for those alkaloids with similar structures. Quantitative analysis of four alkaloids was... 

A single-crystal x-ray structure determination has shown that the borate ion in the pentahydrate and in borax are identical (77). 

Sodium metaborate absorbs C02 from the atmosphere, forming borax and sodium carbonate. Crystals of the tetrahydrate melt in its water of crystallization at about 54°C. The solid-state structure of the tetrahydrate, Na[B(OH)J 2H20, consists of discrete tetrahedral B(OH) 4 groups (90). 

North American Chemical Co. produces borax pentahydrate and decahydrate from Seades Lake brines in both Trona and West End, California (see Chemicals frombrines). The 88 km2 dry lake consists of two brine layers, the analyses of which are given in Table 11. Two distinct procedures are used for the processing of upper and lower lake brines. Borax is produced in Trona from upper lake brines by an evaporative procedure involving the crystallization of potash and several other salts prior to borax crystallization as the pentahydrate (104). A carbonation process is used in West End, California to derive borate values from lower lake brines (105). Raw lower structure brine is carbonated to produce sodium bicarbonate, which is calcined and recrystallized as sodium carbonate monohydrate. The borate-rich filtrate is neutralized with lake brine and refrigerated to crystallize borax. 

Single-crystal x-ray studies have shown that the borate ion in the potassium compound is identical to that found in borax (4) and has the structural... 

Borax, B2O3, forms a glass in which the basic structural elements are triangles with boron at the center surrounded and covalently bonded to three oxygen atoms. Each of the oxygen atoms is shared by three triangles, as shown in Figure 15.12. 

Dietary isoflavones contain at least one hydroxyl group in their structure, which makes it difficult for their analysis by GC/MS without derivatization. Electron impact GC/MS has been used for the analysis of isoflavones. However, prior to analysis, TMS ether derivatives were necessary to increase the volatility and thermal stability of the isoflavones.2 Additionally, a cleanup procedure is usually employed to remove coextracted compounds. Wang et al.113 separated five isoflavone compounds in Puerariae radix within 6 minutes using HPCE in a 20-mM borax-NaOH (pH 10.1) buffer. 

The sodium tetraborates, borax (the decahydrate) and tincalconite (the pentahydrate), have been studied by proton (33, 281), boron-11 (101, 111), and sodium-23 (102, 111) magnetic resonance, and the data is compatible with X-ray studies. Similar agreement with crystal structures has been found with the "B NMR of the hexaborate ion in tunellite (100) and pentaborates (26, 254). Wegener et al. (192, 430)... 

The pentahydrate Na20 2B2O3 5H20 has the same polyborate ion as borax. It crystallizes from aqueous solution above 60°C but is also unstable with respect to kernite in solution above 40°C. In accord with its structure, Na2[B405(OH)j3H20, the first three water molecules are lost at a temperature of 140 or 150°C, with the anhydrous product formed at over 400°C. 

The thermal dehydration of the 1 1 3 (52) and, in particular, the hexaborates of general formula 1 3 x (396) have been studied intensely. Structurally, the 1 2 9 compound resembles borax and has... 

The only definite borate hydrates of cobalt are the CoO - 3B203 - 8H20 and CoO 3B203 10H2O compounds. The octahydrate is prepared by evaporation of acetic acid from cobalt acetate-boric acid mixtures, or by mixing aqueous solutions of cobalt chloride, borax, and boric acid (206). The 1 3 7.5 borate can form as a solid solution and, in the presence of 3% boric acid, affords the decahydrate (117). The crystal structure determination of this 1 3 10 compound shows it to possess the hexaborate ion (380). The IR spectra (402) and thermal decomposition (396) of these compounds have been determined. 

Structure of borax (a) bond lengths in [B4O5 (OtTfi]2- (in pm), (b) perspective view of the anion, and (c) fB405(0II) l chain. 

This zinc borate can normally be prepared either by reacting boric acid with zinc oxide or by reacting borax pentahydrate with zinc sulfate. A recent single crystal x-ray crystallography study showed that it has a structure of Zn[B304(0H)3] (Figure 9.3).47,48 It has been used extensively in PVC,49 polyamide,50 polyolefin,51 52 epoxy,53 phenolics,54 and various elastomers.55... 

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