Bed Ochre

The red ochre, or sesquioxide of iron, is violet red, less easy to melt than iron, unalterable by heat, without action on oxygen or the air.

The sulphuric and hydrochloric acids dissolve it easily.

It exists very abundantly in nature; it is the sesquioxide of iron which colors the argi-laceous earths. It can be obtained by different processes: 1st. By calcining iron in contact with the air; 2d. By decomposing the salts of sesquioxide of iron by ammonia; 3d. By decomposing the nitrate or carbonate of iron by heat. The cheapest process is to decompose the sulphate of sesquioxide by heat.

The sesquioxide of iron has several uses. In the fabrication of matches it is employed to color fancy matches.

The yellow ochre, or sub-sulphate of iron, is a natural product.

Minium

Minium is an oxide of lead, pulverulent, yellowish-red; it is formed of two eq. protoxide of lead, and one bi-oxide, and is represented by 2(PbO)PbOa.

It is prepared in the following manner: -Calcine the lead in a reverberatory furnace till converted into yellow oxide: the mass is well ground, and the powder submitted to the action of a current of water, which carries away the oxide. Collect it, and dry it, and in this state it is called massicot. Have ready some sheet-iron vats, 4 to 5 inches deep, containing 50 pounds of massicot, and put them into the reverberatory furnace which has been used to prepare the massicot, and leave them over night. The oxide absorbs the oxygen, and passes at the state of red oxide or minium.

One fire is not sufficient, and the operation must be repeated several times.

The more thoroughly the oxide is divided, the more readily is it converted into minium.

As found in the trade, it is pure enough for the fabrication of matches. It is employed to color matches, and prepare the bi-oxide of lead.

Bi-oxide of Lead.

This oxide has a flea color. Air and oxygen have no action on it. Heat transforms it first into minium, then into protoxide of lead.

Rubbed in a mortar with sulphur it takes fire, and produces sulphurous acid and sul-phuret of lead. Hydrochloric acid decomposes it into water, chlorine, and chloride of lead.

The bi-oxide of lead does not exist in na-ture. It is represented by PbO2.

It is better for the manufacturer of matches to prepare it himself for it is rarely found in the trade, and generally it is not pure. It is prepared by treating the minium with nitric acid. For this purpose introduce 1 part of minium in a glass or earthen vessel, pour on it 5 to 6 parts of nitric acid diluted with its weight of water; raise the temperature by degrees to ebullition, shaking from time to time. The minium is decomposed; it gives its protoxide to the acid, and the bi-oxide is set free. When the decomposition is achieved, which docs not take more than half an hour, fill the vessel with hot water, and let to settle, the bi-oxide deposits. Decant the clear liquor which contains the nitrate of lead, and substitute for it pure warm water; decant anew, and continue the same operation until the water has no taste. Collect the precipitate on a filter, and dry it at a gentle heat.

It can also bo prepared in the following manner: -

Boil a solution of acetate of lead with an excess of chloride of lime in solution. Wash the precipitate on a filter to eliminate the salts, and dry it at a gentle heat.

This oxide is now largely used in the preparation of matches.

Binoxide Of Manganese

The binoxide of manganese, such as found in the trade, is pure enough; but it is better to treat the commercial oxide by diluted hydrochloric acid until all effervescence has stopped. Let it settle, decant, and wash the residue with warm water until this water has no longer any taste. Collect the oxide on a filter, and dry it.