[578] Usher and Priestley, Proc. Roy. Soc., B, 77, 369 (1905); 78, 318 (1908).
[579] Tollens, Ber. d. chem. Ges., 15, 1635 (1882).
[580] [Ag+] × [NH3]2 / [Ag(NH3)2+] = 1 / 107.
[581] Methylene CH2, itself, has never been isolated, but derivatives of it are known, such as the cyanides, C(NH), C(NK) (see pp. [66], [237]).
[582] Potassium cyanide, ═C(NK), is a powerful reducing agent (see p. [89]).
[584] If a negative charge is an electron, a positive charge the absence of an electron in an atom, the bivalent carbon atom loses two electrons, when it is oxidized.
[585] See Stieglitz, Science, 27, 774 (1908).
[586] The oxidation occurs essentially in the same manner as described (p, 292) for the action of formaldehyde on ammoniacal silver solution, when they are brought together in a single vessel. In the present case, where the action is used to produce an electric current, there is a migration of negative ions into the formalin solution through the salt-bridge (p. [254]). For every two silver ions discharged on the electrode in the silver nitrate solution, two hydroxide ions are liberated in the formaldehyde solution, as a result of this migration, and they combine with the oxidized carbon atom. The oxidation may be expressed, then, simply as follows:
(NaO)HC± + 2 ⊕ + 2 HO− → (NaO)HC2+ + 2 HO− →
(NaO)HC:O + H2O.