Specificity of Electrolytes

The index of electrophoretic mobility as used in this article is defined in Section IV (p. 82). 

The Raman spectrum of the aqueous borate ion and x-ray studies on boron minerals have shown that the borate ion has tetrahedral symmetry and is, in all likelihood, B(OH)4 , In 3 Af sodium perchlorate solution at 25° and with a total concentration of boron of B 0.025 M, essentially the mononuclear species boric acid, B(OH)s, and the anion B(OH)4 seem to be present, whilst, for B 0.025 M, two polynuclear species, B30s(0H)4 and B308(0H)5 , can also be detected. This means that boric acid does not act as a proton donor but as a Lewis acid, accepting the electron pair of the base (for example, OH ) to form the tetrahedral anion B(OH)4 . 

Most esters and complexes between boric acid and borate ions, respectively, and polyhydroxy compounds can be formulated as follows  

The 0-0 distances for trigonal and tetrahedral boron are 2.36 to 2.39 A. and 2.40 to 2.44 A., respectively. It thus appears that the borate ion would form complexes with those polyhydroxy compounds in which the oxygen atoms of at least two hydroxyl groups are separated by, or can easily approach each other to, a distance of approximately 2.4 A. Such a distance is found in the a s-1,2-diols of five-membered ring compounds 

The 0-0 distances in the planar, zigzag conformation of 1,3-propane-diol and acyclic trans- and cfs-1,3-diols are 4.84, 3.43, and 2.51 A., respectively. By rotation about C-C bonds, these can be reduced to 1.74 A., when C-1, C-2, C-3, and the oxygen atoms are coplanar. Thus, with such compounds, the borate ion, B(0H)4 , would fit well, to form puckered, six-membered rings. The resolution of cis- Sa)[ Mo B) 0.18] and rans-2,4-pentanediol (6a) ]Afo(B)0] shows that the mobility is decreased when the six-membered ring [(Sb) and (6b)] contains an axial alkyl group. 2-Methyl-1,3-pentanediol yielded, when subjected to electrophoresis, two components [ilf( (B) 0.08 and 0.24]. Presumably, the sub- 

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