Murexide





The red obtained from this substance created a great deal of interest

among printers and dyers on its introduction in 1857, or thereabouts.

For purity and brilliancy of shade it was not excelled by any other

colour, but not being able to stand the effects of air and light, its

employment was limited. We are not aware that murexide has yet been

brought forward as a pigment, and judging from its character as a dye,

it would scarcely enrich the palette. Dyes and pigments have much in

common, and a fugitive dye cannot be expected to furnish a permanent

pigment.



Murexide is produced by the action of ammonia on alloxan, which is

itself derived from the uric acid of guano by treatment with nitric

acid, and was known nearly forty years back to stain the fingers and

nails red. The first murexide sent into the market was a reddish-purple

powder, dissolving in water with a fine purple tint, leaving a little

residue undissolved. Owing to improvements in manufacture, it is now

capable of being prepared almost chemically pure, and with that green

metallic reflection peculiar to several coal-tar salts and the wings of

certain insects. When sulphuretted hydrogen is passed through a

concentrated solution of murexide, it is immediately decoloured; a fact

which renders it likely that murexide pigments would be as liable to

suffer from an impure atmosphere, as from exposure to light and air.



When an alkaline solution of murexide is precipitated by an acid, a

light shining powder results, called purpuric acid. This dissolves in

alkalies, and combines with metalline bases to form various coloured





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