1. The Merck Index,9th edn., Merck & Co., Rahway, New Jersey, 1976, p. 254.
2. M. E. Chevreul, Ann. Chim. Phys. 2, 155 (1817).
3. E. Andre and T. François, Compt. Rend. 183, 663 (1926).
4. F. Krafft, Ber. Dtsch. Chem. Ges. 17, 1627 (1884).
5. E. Ludwig, Z. Phys. Chem. 23, 38 (1892).