1. Colles, J. Chem. Soc.,89, 1250 (1906).
2. Dahms, Ann. chim. phys., [7]18, 140 (1899).
3. de Coppet, Ann. chim. phys., [7]16, 275;18, 142 (1899).
4. Faucon, Compt. rend.,148, 39, 1189 (1909); Ann. chim. phys., [8]19, 70 (1910).
5. Grimaux, Compt. rend.,76, 486 (1873); Bull. soc. chim. [2]19, 393 (1873).