| 摘要 |
Artificial pyrolusites, i.e. those obtained by precipitation from a manganese salt solution by means of an oxidizing or reducing agent, especially suitable for use in the construction of Leclanche cells, are dehydrated to a water content of 15 to 35%, preferably 20 to 23%, while being continuously mixed and/or divided, as e.g. in a drum drier and preferably with a grinding agent, at a temperature not exceeding 150 DEG C. and preferably above 65 DEG C. The dehydration may be effected under subatmospheric pressures and lower temperatures. In a modification of the process, a pyrolusite which had its water content reduced to less than 15% may be steam-treated or water vapour-treated to obtain the product containing 15 to 35% water. A preferred starting material is obtained by oxidizing at pH 5 to 9, an aqueous solution of a bivalent manganese salt with chlorine or hypochlorite. The product of the invention may be admixed with natural or electrolytic pyrolusite. In the example, which includes for comparison static dehydration of pyrolusite in an oven on trays to an identical water content, use is made of a rotary drum drier charged with porcelain balls. Specification 939,240 is referred to. |
