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BROMIDE OF POTASSIUM. 521 ;

watery liquid, when immediately violent reaction takes place, the
water is decomposed, with the development of considerable heat,
by the production of potassium and sodium hydroxide and hydro-
gen. The sodium and potassium hydroxides unite with the fatty
substances to form soap, which accounts for the characteristic
odor. The compound, which is contained in a tube, is applied
to the root-canal as follows : When the cork stopper is removed
a paraffin layer covering the preparation is exposed. A barbed
nerve-extractor is then pushed through this paraffin layer into
the preparation, and upon gently withdrawing the instrument
small particles of the potassium and sodium compound adhere to
the barbs of the instrument, in which condition it is ready for
introduction into the pulp-canal. Dr. Schreier advises care as to
its use, especially avoiding an excess at any one application
otherwise the action would be too violent. The rubber-dam
should be applied in all cases. Practical tests of this compound
have given satisfactory results.

POTASS! BROMIDUM—BROMIDE OF POTASSIUM.
Formula.—KBr.
Derivation.—Bromide of potassium is obtained by adding a
solution of pure carbonate of potassium to a solution of bromide
of iron. The iron being precipitated, the bromide of potassium
is obtained from the solution by evaporation. It is in the form
of white crystals, without odor, wholly soluble in water, and but
sparingly soluble in alcohol, and having a pungent, saline taste.
Medical Properties and Action.—Bromide of potassium is stim-
ulant, sedative, narcotic and antispasmodic, and, being absorbed
into the system, can be detected in the blood, urine, faeces and
mucus. If administered in considerable quantity, the action of
the heart, respiration, and the temperature are depressed, and
although in some cases a transient excitement may be caused by
large doses, the effect of this agent is to induce a sound and re-
freshing sleep, and if its use is long continued, a constant drowsi-
ness is experienced. Bromide of potassium has also the power
of lessening the sensibility to pain, especially causing a loss of
sensibility of touch in the case of the mucous membrane and