Antimony vermilion burns with production of sulphur dioxide and white fumes without smell when heated in the oxidising flame; when fused with soda before the blowpipe, it gives a white brittle bead of metallic antimony. Vermilion volatilises in the oxidising flame and gives a smell of sulphur dioxide. Mercuric iodide readily fuses and volatilises. Realgar volatilises. When heated with soda in the reducing flame, white fumes with an odour of garlic are produced. REACTIONS OF THE BLUE PIGMENTS. +---------------+---------------+----------+----------+------------+ | Pigment. | Hydrochloric | Caustic | Ammonium | On Heating.| | | Acid. | Soda. | Sulphide.| | +---------------+---------------+----------+----------+------------+ |Prussian, |Dissolve to |Decolour- |Liquid |Blackened. | |Chinese, |green solution,| ised, |yellowish | | |Paris, |then yellow. |brown |green. | | |Turnbull’s, | |residue. | | | |and Brunswick | | | | | |blue | | | | | | | | | | | |Mountain blue |Dissolves to |Blackened.|Blackened.|Blackened. | | |yellowish-green| | | | | |solution. | | | | | | | | | | |Ultramarine |Rapidly |Unchanged.|Unchanged.|Unchanged. | | |decomposed | | | | | |with evolution | | | | | |of sulphuretted| | | | | |hydrogen. | | | | | | | | | | |Smalts |Almost |Unchanged.|Blackened.|Fuses at | | |unaltered, | | |a high | | |greenish | | |temperature.| | |solution on | | | | | |long boiling. | | | | | | | | | | |Cobalt blue |Unchanged. |Unchanged.|Unchanged.|Infusible | | | | | |and | | | | | |unchanged. | +---------------+---------------+----------+----------+------------+ _On Heating on Charcoal_:—Prussian, Chinese, Paris, Turnbull’s and Brunswick blue are turned black, the residue colours the borax bead pale brown in the oxidising flame, and pale green in the reducing flame.