In the reduction flame it fuses to a fine green bead.  The addition of a little tin renders the green still deeper.

Sesquioxide of chromium fuses with carbonate of soda upon platinum foil to a brown or yellow bead, which, upon cooling, appears of a lighter color and transparent (chromate of sodium).

When fused with soda upon charcoal, the soda is absorbed, and the green oxide is left upon it, but is never reduced to the metallic state.

Chromic Acid (CrO^{3}) crystallizes in the form of deep ruby red needles.  It is decomposed into sesquioxide and oxygen when heated.  This decomposition is attended with a very lively emission of light, but this is not the case if the chromic acid has been attained by the cooeperation of an aqueous solution, unless the reduction is effected in the vapor of ammonia.  Before the blowpipe chromic acid produces the same reactions as the sesquioxide.

(l.) Manganese (Mn).—­This metal occurs in considerable abundance, principally as oxides, less frequently as salts, and sometimes in combination with sulphur and arsenic.  It is found in plants, and passes with them into the animal body.  In the metallic state, it is found frequently in cast iron and steel.  It is a hard, brittle metal, fusible with difficulty, and of a light grey color.  It tarnishes upon exposure to the air and under water, and falls into a powder.

Protoxide of Manganese exists as a green powder; as hydrate separated by caustic alkalies, it is white, but oxidizes very speedily upon exposure to the air.  The protoxide is the base of the salts of manganese.  These salts, which are soluble in water, are decomposed when heated in the presence of the air—­except the sulphate (MnO, SO^{3}), but if the latter is exposed to ignition for awhile, it then ceases to be soluble in water, or at least only sparingly so.

Sesquioxide of Manganese (Mn^{2}O^{3}) Occurs very sparingly in nature as small black crystals (Braunite) which give, when ground, a brown powder.  When prepared by chemical process, it is in the form of a black powder.  The hydrate occurs sometimes in nature as black crystals (manganite).  By digestion with acids, it is dissolved into salts of the protoxide.  With hydrochloric acid, it yields chlorine.

The prot-sesquioxide of manganese (MnO + Mn^{2}O^{3}) occurs sometimes in black crystals (hausmannite).  Prepared artificially, it is in the form of a brown powder.

Peroxide of Manganese (MnO^{2}) occurs in considerable abundance as a soft black amorphous mass, or crystallized as pyrolusite, also reniform and fibrous.  It is deprived of a part of its oxygen when exposed to ignition.  It eliminates a considerable quantity of chlorine from hydrochloric acid, and is thereby converted into chloride of manganese (ClMn).

Most of the manganese compounds which occur in nature yield water when heated in a glass tube closed at one end.  The sesquioxide and peroxide give out oxygen when strongly heated, which can be readily detected by the increased glow which it causes, if a piece of lighted wood or paper is brought to the mouth of the tube.  The residue left in the tube is a brown mass (MnO + Mn^{2}O^{3}).