1. A. E. Hill, Treatise of Phys. Chem, D. VanNostrand Co, N. Y., Page 406 (1925).
2. Alexejew, Wied. Ann.,28, 305 (1886).
3. F. Emich, Ztschr. analyt. Chem.,54, 495 (1915).
4. Alexejew, loc. cit..
5. E. Paterno andG. Ampola, Gazz. chim. Ital.,27, I, 481 (1897).