490
ELEMENTS OF MATERIA MEDICA.
and Dr. Duncan ( Edinb. Dispensat.) direct more nitric acid to beused than is contained in the official formulae.
Properties. —When fresh prepared this ointment has a fine goldenyellow colour, a butyraceous consistence, and a remarkable nitrousodour. It is very apt to become grey when mixed with other ointments,in consequence of their deoxidizing powers. It should be spread withwooden or ivory spatulas.
Composition. —When fresh prepared this compound contains the fol-lowing substances:—
Elaidine.
Yellow matter soluble in alcohol.
Elai'date of mercury (mercurial soap.)
Nitrate of mercury.
Elaidine is a white saponifiable fat, fusible at 97° F. very soluble inether, but requiring 200 times its weight of boiling alcohol to dissolve it.When mixed with potash or soda it is converted into glycerin and elaidicacid.
Physiological Effects. — It is an irritant and slight caustic.When it has undergone decomposition by keeping, it irritates ulcersexceedingly, and even excites slight erysipelatous inflammation.
Uses. —We employ it as a stimulant and alterative in chronic diseasesof the skin, more particularly those affecting the hairy scalp, as the dif-ferent forms of porrigo, in which it is exceedingly efficacious. It is alsoused as a dressing to ulcers —to stimulate and cleanse them—as in foulsyphilitic sores and phagedacnic ulcers. Lastly, it is employed inophthalmic diseases —more particularly ophthalmia tarsi, or psorophthal-mia, in which it is applied (mixed with its own weight of almond oil) bymeans of a camel’s-liair pencil to the lids, frequently with such advantagethat some have regarded it a specific in this complaint.
Hydrar'gyri Ace'tas. — Ac'etate of Mer'cury.
History. —This compound was known to Lefebure in the 17th century.
Preparation. —In the Dublin Phamiacopoeia the directions for pro-curing it are the following:—Add eleven parts of diluted nitric acid tonine parts of mercury, and when the effervescence has ceased let themixture be digested that the metal may be dissolved. Add this to aboiling solution of nine parts of acetate of potash in a hundred of distilledwater acidulated with vinegar; filter through a double hair-cloth, and letit cool, that crystals may form. Wash them with cold distilled water, anddry on paper with a gentle heat. In the Edinburgh Pharmacopoeia alarger quantity of nitric acid is used and the vinegar omitted, as well asthe directions for filtering through linen.
By the mutual action of diluted nitric acid and mercury we obtain aprotonitrate of mercury (vide p. 463.) When this is mixed w ith acetateof potash double decomposition takes place : nitrate of potash andprotoacetate of mercury being formed. To prevent precipitation of theyellow subnitrate of mercury, excess of acid (acetic, Ph. Dub., nitric, Ph .Ed.) should be employed : and by filtering, while hot, any which may heformed would be separated before the acetate has deposited.
Properties. —This salt occurs in white, micaceous, flexible scales,which are inodorous, but have an acrid taste. It blackens by light.When heated it is resolved into carbonic acid, acetic acid, and mercury.