[477] In the absence of any added cyanide, it combines with itself. Silver cyanide, according to Bodländer's results, is, in saturated solutions, chiefly (AgCN)2 or Ag[Ag(CN)2], i.e. Ag─[N═C═C═N─Ag].
[478] See p. [225], footnote 4.
[479] Werner has developed quite a different theory of the structure of complex ions. (Cf. Nernst, Theoretical Chemistry, p. 374 (1904).)
[480] Sherrill, Z. phys. Chem., 43, 721 (1903).
[481] In Nessler's reagent, Fresenius' Qualitative Analysis, p. 141.
[482] Cf. Remsen, Am. Chem. J., 11, 291 (1899); 14, 81 (1892) (Stud.).
[483] For instance, for arsenious acid we have
3 H+ + AsO33− ⇄ H3AsO3 ⇄ As3+ + 3 HO−
and, therefore, [As3+] × [HO−]3 / ([AsO33−] × [HO+]3) = k1. Since [H+] = k′HOH / [HO−] (p. [176]), we have further, [As3+] × [HO−]6 / [AsO33−] = k2. And since we may derive the relation [HO−]2 = k3 × [O2−], by considering the primary and the secondary ionization of water (see pp. [246], [278]), we have, finally, [As3+] × [O2−]3 / [AsO33−] = K. The constants for the primary and the secondary ionization of water are included in the value of K.
[484] Fitzgerald and Lapworth, J. Chem. Soc. (London), 93, 2163 (1908); Lapworth, ibid., 2187. Vide also Franklin on the characteristics of the NH4+ ion in liquid ammonia, Am. Chem. J., 23, 305 (1900).