ute, and forming a
very porous mass. When the plate is exposed to the air, rapid
oxidation takes place because the oxygen of the air has a very large
surface to act upon. The oxidation causes the lead to become heated.
The heating, of course, raises the temperature of the electrolyte, and
the hot acid attacks both grids and lead.

Fully charged negatives should therefore be watched carefully when
removed from a battery. When they become heated and begin to steam,
they should be dipped in water until they have cooled. They may then
be removed from the water, but should be dipped whenever they begin to
steam. After they no longer heat, they may be left exposed to the air.

This method of dipping the negatives to prevent overheating has always
been followed. However, the Electric Storage Battery Company, which
makes the Exide batteries, does not take any steps to prevent the
heating of the negatives when exposed to the air, stating that their
plates are not injured by the heating which takes place.

Negatives With Very Hard Active Material

This is the characteristic condition of badly sulphated negatives. The
active material may be as hard as a stone. The best method of treating
such negatives is to charge them in distilled water. See Chapter 15.

Bulged Negatives

This is a characteristic of a repeatedly over-discharged negative. The
lead sulphate which forms as a battery discharges is bulkier than the
spongy lead, and the lead expands and bulges out between the ribs of
the grid.

Negative With Soft, Mushy Active Material

1. High Gravity. Gravity above 1.300 causes the acid to act upon the
spongy lead and soften it.

2. Heat will soften the spongy lead also. The softened spongy lead is
loosened and falls from the grids, as shown in Fig. 211. Little can be
done for such negatives.

Negatives With Roughened Surface

This is caused by slight overheating, and is not a serious condition.

Frozen Positives

A battery which is allowed to stand in a cold place while completely
discharged will freeze. The water in the electrolyte expands as it
freezes, cracking the rubber jars and bulging out the end of the
wooden case. As the electrolyte which fills the pores of the positive
plates freezes and expands, it breaks the active material loose from
the grids. When the battery thaws, the active material does not go
back into the grids. When such a battery is opened, and the groups
separated, the po