Present name. - Moist Hydrated Ferric Oxide. Fe2O3,H1O.
The British Pharmacopoeia orders this to be prepared as follows: -
Solution of Persulphate of Iron .
4 fluid ounces;
Solution of Soda ....
33 fluid ounces;
Distilled water ....
Mix the solution of Persulphate of Iron with a pint of the distilled water, and add this gradually to the solution of Soda, stirring them constantly and briskly. Let the mixture stand for two hours, stirring it occasionally, then put it on a calico filter, and, when the liquid has drained away, wash the precipitate with distilled water, until what passes through the filter ceases to give a precipitate with Chloride of Barium. Lastly, enclose the precipitate, without drying it, in a stoppered bottle, or other suitable vessel, from which evaporation cannot take place. This preparation, when used, should be recently made.
Characters and Tests. - A soft moist pasty mass, of a reddish-brown colour. Dissolves readily in diluted Hydrochloric Acid without the aid of heat, and the solution gives a copious blue precipitate with the yellow, but not with the red Prussiate of Potash. A little of it dried at 212° until it ceases to lose weight, gives off moisture when heated to dull redness in a test-tube.
Preparation. - Used chiefly for making Ferrum Aceticum.