Pyroborates

Two rather different configurations of the pyroborate ion have been found, in the magnesium and cobalt salts. In Co2B2 0s, (a), the planes of the BO3 groups make angles of 7° with the plane of the central B—0—B system and are twisted in opposite directions (mean B-0 approximately 1-30 A). In MgjB205, (b), the 

8303(011)3 molecules in a layer of one form of crystalline metabolic acid. 

Metaboric acid is known in three crystalline modifications, which provide a good example of monotropism (Fig. 24.12) and of the increase in density with change from 3- to 4-coordination of B (Table 24.4). The monoclinic form is readily prepared by the dehydration of H3BO3 in an open vessel at 140°C quenching of the molten material gives a glass which later recrystallizes as the orthorhombic form. If the melt is held at 175°C the most stable (cubic) form is slowly precipitated, while complete dehydration at about 230°C yields B2O3. 

Orthorhombic metaboric acid is built of molecules 8303(011)3 which are linked into layers by O—H—O bonds (Fig. 24.13). Monoclinic metaboric acid is apparently built of chains of composition [8304011(0112)], recognition of the OH group and the H2O molecule resting on the location of the H atoms. The direct bonding of a water molecule to B is most unexpected. Cubic HBO2 has a framework structure built from tetrahedral BO4 groups with hydrogen bonds between certain pairs of O atoms. 

A surprising difference is found between the structures of the B3OI ions in NaaBaOg and K3B3O6, the structures of which have been carefully refined  

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Chemical Designations - Synonyms Borax, anhydrous Sodium biborate Sodium pyroborate Sodium tetraborate,anhydrous Chemical Formula Na2B407. 

Naturally, the flux employed will depend upon the nature of the insoluble substance. Thus acidic materials are attacked by basic fluxes (carbonates, hydroxides, metaborates), whilst basic materials are attacked by acidic fluxes (pyroborates, pyrosulphates, and acid fluorides). In some instances an oxidising medium is useful, in which case sodium peroxide or sodium carbonate mixed with sodium peroxide or potassium nitrate may be used. The vessel in which fusion is effected must be carefully chosen platinum crucibles are employed for... 

Sodium borate decahydrate sodium tetraborate decahydrate sodium biborate sodium pyroborate... 

Synonyms/compounds Sodium borate sodium pyroborate boric acid, disodium salts... 

Boric acid on slow heating loses water around 130°C, forming metaboric acid HBO2 which converts into different crystal modifications that depend on the temperature. Further heating dehydrates metaboric acid to pyroboric acid, H2B4O7 and boric oxide, B2O3. 

Pyroboric Acid Tetrakis-ftrifluoro-acctox>]- VI/3. 247 (Kundens.)... 

Borates. A general term for salts of acids based on boron, such as metaboric HB02, perboric HBOs, tetra- or pyroboric H2B407, boric or orthoboric HjBOj and others. Props of various borates are given in Refs 1,3,5,6 7 and their uses in some pyrotechnic compns are listed in Ref 8 Following is the list of some borates". 

Synonyms Biborate of soda, Biborate of sodium, Borate of soda, Borate of sodium, Purified borax, Pyroborate of soda, Sodium biborate, Sodium borate, Sodium pyroborate, Sodium tetraborate,Tetraborate of soda. 

Methyl borate Section of borax structure Pyroborate ion... 

IV.23 BORATES,B03 ,B407r,B02 The borates are derived from the three boric acids orthoboric acid, H3B03, pyroboric acid, H2B407, and metaboric acid, HB02. Orthoboric acid is a white, crystalline solid, sparingly soluble in cold but more soluble in hot water very few salts of this acid are definitely known. On heating orthoboric acid at 100°, it is converted into metaboric acid at 140° pyroboric acid is produced. Most of the salts are derived from the meta-and pyro-acids. Owing to the weakness of boric acid, the soluble salts are hydrolysed in solution and therefore react alkaline. 

To study these reactions use a OTm solution of sodium tetraborate (sodium pyroborate, borax) Na2B407.10H2O. 

Thompson P. D., Huang J. F., Smith R. W. and Keszler D. A., The mixed orthoborate pyroborates Sr2Sc2B40n and Ba2Sc2B40n pyroborate geometry, J. Solid State Chem. 95 (1991) pp. 126-135. 

This angular variation is not unexpected in view of the isoelec-tronic relationship between the pyroborate group, the molecule N2O5 (5), and the malonate anion, where considerable rotations about the and C-O bonds are also observed. 

The compound Ba5(B205)2p2 represents the first established example of a pyroborate halide. The pyroborate group in this compound exhibits the largest deviation from planarity of any such unit. ... 

The second basic type of structural units is usually built up of several FSU (from 2 to 5) joined by sharing common O atoms. There is a rather limited number of these anionic groups. They are shown in Fig. 1, II,1 and II.2 and designated below as combined basic structural units (CSU). Only two of them, 2A and 3A, can be isolated in the structures of anhydrous pyroborates and some metaborates, respectively. The rest of the structural units of this type are as components of various one-, two- and three-dimensional BnOm polyanions by sharing their free 0 atoms. 

Borax decahydrate boric acid disodium salt E285 natrii tetraboras sodium biborate decahydrate sodium pyroborate decahydrate sodium tetraborate decahydrate. 

Synonyms borax glass disodium tetraborate anhydrous fused borax fused sodium borate sodium pyroborate sodium tetraborate anhydrous. 

Orthoborates discrete BO ions Pyroborates discrete B2OS ions 0... 

Patent Number US 5482989 A 19%0109 CALCIUM PYROBORATE AS A MICROBIOCIDE FOR PLASTICS... 

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