or (Muriate of Potassa).--Dissolve half an
ounce of carbonate of potassa in water, and neutralize with muriatic
acid. Upon concentrating the solutions, cubic crystals will be
obtained, having a taste similar to common salt. They consist of
potassium and chloride, and when dissolved in water they may be
regarded as muriate of potassa.

Chloride of Lime.--Mix half an ounce of slacked lime (hydrate of lime)
with six ounces of water, and conduct into this milk of lime, with
frequent agitation, as much chlorine gas as will evolve from two ounces
of muriatic acid and half an ounce of black oxide of manganese. The
liquid clarifies by standing; may be regarded as a solution of chloride
of lime, and must be protected from the air and light. It may also be
made without putting in the water with the hydrate of lime, by merely
passing the chlorine into the hydrate of lime. This last is by some
used in preparations for accelerating the operation of taking
Daguerreotypes, but when used for this purpose it is in small
quantities.

Chloride of Calcium.--To one part of water add two parts of muriatic
acid, and add pieces of common chalk until effervescence ceases; then
filter through cotton cloth and evaporate it by placing it in all
earthen or porcelain dish, over a slow fire, to the consistency of a
syrup. When cooling, large prismatic crystals of chloride of calcium
are formed. These must be quickly dried by pressing between folds of
blotting paper and kept carefully excluded from the air, as it readily
attracts hydrogen. For most daguerreotype purposes, the syrup may be
at once evaporated to dryness. This is frequently placed in the iodine
coating box for the purpose of keeping the atmosphere dry. It is so
easily made that every operator can provide himself with it in a short
time, and at little expense.

Chloride of Gold.--Is prepared by dissolving gold in aqua regia, a
composition of one part of nitric to two parts of muriatic acid. Gold
foil is the best for our purposes; coin, however, answers, in most
cases, for the daguerreotype operator, as the alloy, being so slight is
not noticed in the gilding process. When the latter is used, it will
facilitate the operation to beat it out, forming a thin sheet, and then
cutting in small strips. Where purity is required, foil is better.
The gold is placed in three or four times its own weight of the above
acids. For this purpose, an evaporating dish is best (a common sauce