Abstract :
A new method for measuring the rate of sulphation of storage battery plates was recently devised al the Bureau of Standards by Vinal and Ritchie (Technologic Paper 225). This consisted of periodic weighings of plates suspended in electrolyte. The present paper is an extension of this work. Detrimental impurities when present in the solution may (1) corrode the plate, (2) accelerate the formation of lead sulphate, or (3) be deposited in the pores of the plate. In any case, the weight of the plate changes and this affords the most sensitive and exact means which we have for estimating the extent and nature of the reaction. A physical meaning can be given to the rather vague term “local action.” It was found that electrolyte, containing only one part of platinum in ten million parts of the solution, increased the local action at the negative plates by 50 per cent. Copper, like platinum, deposits on the negative plates, but produces less effect. Iron is of unusual interest because it greatly accelerates the formation of lead sulphate at the negative plate. The reaction of the positive plates is slower, which mitigates its detrimental effects to some extent. Manganese is particularly destructive to the positive plates. The results of our experiments indicate that the reactions of manganese compounds in the battery are somewhat different from the previously accepted theories. Manganese in the form of manganese dioxide is deposited on the positive plates covering the active material, closing the pores and causing a part of the charging current to be wasted. The work is being extended to include the effect of other impurities.
