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White Precipitate

This is the found in large quantities in mineral form, and ammonio-chloride of mercury, and is prepared is known as Iron pyrites. It may also be oband is prepared | is known as Iron pyrites. It may also be obtained by projecting a mixture of 5 parts sul- digested in water (or very weak spirit), gives phur, and 4 parts iron filings, into a red-hot a solution which is colored violet by the procrucible, excluding the air as much as possi- tosalts of iron. ble. It melts easily, and takes sharp casts, 4153. Anhydrous Sesquioxide of and may be colored red with vermilion.

Iron. A pure anhydrous sesquioxide is ob- 4149. Hydrated Protosulphuret of tained by precipitating a solution of sesqui- Iron. This is a black, insoluble substance, sulphate or sesquichloride of iron with amrapidly decomposed by exposure to the air. A monia in excess, and washing, drying, and neutral solution of protosulphate of iron made igniting the resulting hydrated peroxide. with recently boiled or distilled water, is pre- 4154. Jewelers' Rouge. The best cipitated by adding a solution of hydrosul- jewelers' rouge is prepared by calcining the phuret of ammonia, or of sulphuret of potas- precipitated peroxide of iron (see No. 4153) sium. Collect the precipitate on a filter, until it becomes scarlet. The rust of iron wash it as quickly as possible with recently contains some combined water, and is more boiled water, squeeze in a linen cloth, and soluble than the oxide prepared by calcinapreserve in its pasty state under water. tion; but it is less soluble than that recently

This preparation of iron is proposed by precipitated from its solution in an acid. This Mialhe as an antidote to the salts of arsenic, is also called Colcothar, Crocus, or Crocus antimony, bismuth, lead, mercury, &c., and Martis. to arsenious acid, more especially to white 4155. Hydrated Sesquioxide of Iron. arsenic and corrosive sublimate. On contact Take 4 ounces sulphate of iron; 3½ fluid ounwith the latter substance it is instantly con- ces oil of vitriol; water, 1 quart; mix, disverted into protochloride of iron and sul- solve, and boil, then gradually add 9 fluid phuret of mercury, two comparatively inert drachms nitric acid; stirring well and boilsubstances. ing for a minute or two after cach addition, 4150. Hydrated Persulphuret of until the liquor yields a yellowish-brown pre- Iron. Prepared by adding, very gradually, cipitate with ammonia, when it must be fila diluted solution of sulphuret of potassium, or tered and precipitated with 34 ounces strong of hydrosulphuret of ammonia, to a neutral liquor of ammonia, rapidly added and well solution of persulphate of iron, collecting, &c., mixed in; collect, wash well with water, the precipitate, in the same way as in hydra- drain on a calico filter, and dry at a heat not ted protosulphuret of iron. Bouchardat and exceeding 180° Fahr. When intended as an Sandras recommend this persulphuret as a antidote for arsenic it should not be dried, but substitute for the protosulphuret, to which, they say, it is preferable. kept in the moist or gelatinous state. It should be kept in a well-stoppered bottle filled