Synonym. - Hydrargyri Oxidum Rubrum.

Present name. - Mercuric Oxide. HgO.

Red Precipitate.

This is prepared as follows: -

Take of

Mercury, by weight ....

8 ounces;

Nitric Acid .....

4 1/2 fluid ounces;

Water . . . . . .

2 fluid ounces.

Dissolve half the Mercury in the Nitric Acid diluted with the water, evaporate the solution to dryness, and with the dry salt thus obtained triturate the remainder of the Mercury until the two are uniformly blended together. Heat the mixture in a porcelain dish, with repeated stirring, until acid vapours cease to be evolved, and, when cold, enclose the product in a bottle.

Characters and Tests. - An orange-red powder, readily dissolved by Hydrochloric Acid, yielding a solution which, with Caustic Potash added in excess, gives a yellow precipitate, and with solution of Ammonia a white precipitate. Entirely volatilized by a heat under redness, being at the same time decomposed into Mercury and Oxygen. If this be done in a test-tube, no orange vapours are perceived.

Preparation. - Trituration.