hless casting.

In a shop having an ordinary room temperature, it is generally
unnecessary to heat the moulds before making up a number of castings.
If it is found, however, that the first castings are defective due to
the cold mould chilling the lead, the mould should be heated with a
soft flame. After a few castings have been made, the mould will become
hot enough so that there will be no danger of the castings becoming
chilled.

When the castings have cooled sufficiently to be removed, strike the
mould a few blows with a wooden mallet or a rawhide hammer to loosen,
the castings before opening the mould. The castings may then be
removed with a screwdriver.

Cracked castings indicate that the mould was opened before the
castings had cooled sufficiently, or that there is too much antimony
in the castings. The remedy is to let the castings cool for a longer
time, or to add pure lead to the melting pot.

HANDLING AND MIXING ACID

The electrolyte used in the battery is made by mixing chemically pure
concentrated Sulphuric Acid with chemically pure water. The
concentrated acid, or "full strength" acid cannot be used, not only
because it would destroy the plates, but also because water is needed
for the chemical actions which take place as a cell charges and
discharges. The water therefore serves, not only to dilute the acid,
but also to make possible the chemical reactions of charge and
discharge.

The full strength acid has a specific gravity of 1.835, and is mixed
with the water to obtain the lower specific gravity which is necessary
in the battery. The simplest scheme is to use only 1.400 specific
gravity acid. This acid is used in adjusting the specific gravity of a
battery on charge in case the specific gravity fails to rise to a high
enough value. It is also used in filling batteries that have been
repaired.

Acid is received from the manufacturer in ten gallon glass bottles
enclosed in wooden boxes, these being called "carboys." Distilled
water comes in similar bottles. When distilled in the shop, the water
should be collected in bottles also, although smaller ones may be used.

Neither the acid nor the water should ever be placed in any vessels
but those made of lead, glass, porcelain, rubber, or glazed
earthenware. Lead cups, tanks, and funnels may be used in handling
electrolyte, but the electrolyte must not be put in containers made of
any metal except lead. Lead is rather expensive for making such