Hydrate of Lime.--The operation by which water is combined
with lime is called slaking. Take a piece of quick lime,
common lime used in mortar, and immerse it in warm water for
about fifteen seconds; then place it in an iron or tin vessel.
It will soon begin to swell, evolving a great deal of heat and
emitting steam, and soon falls into a fine powder, hydrate of lime.
This should be well stirred and allowed to cool, and then
bottled in order to prevent it from giving off the hydrate
and recovering the carbonic acid from the atmosphere.
The last is detrimental to its use with bromine, and is one
cause of the complaint that "it will not take bromine."
The hydrate of lime should, not be dried over a heat,
as has been supposed by many, for in that case
the hydrogen is expelled and it returns to a carbonate.
It is advisable to cool it in a damp place like a ground cellar.
Much of the lime in our market will not, except it be quite damp,
combine with the bromine. This is owing to impurities.
Nothing is equal to oyster-shell lime, which I use altogether.

Bromide of Lime.--In preparing large quantities of this, we adopt
the following method: Fill a four-quart bottle about two-thirds full
of hydrate of lime; pour into this about one or two ounces of bromine;
then shake well, add more of the bromine, shake well and let it stand
for a few hours, adding sufficient bromine to give it a fine red color.
It is better when kept in the large bottles, as it forms a more
perfect combination: in other words it improves by age.

Use.--Coat over the iodine to a rose red and then over this mixture
to a purple or slate; recoat over the first about one fourth as long