Century Dictionary and Cyclopedia
- n. The purpurate of ammonia of Prout (probably C8H8N6O6). It crystallizes in four-sided prisms, two faces of which reflect a green metallic luster. The crystals are transparent, and by transmitted light are of a garnet-red color. It forms a brownish-red powder, and is soluble in caustic potash, the solution having a beautiful purple color. In 1855 and 1856 this substance was largely used as a dye for producing pinks, purples, and reds, but the introduction of aniline colors put an end to its use.
- n. organic chemistry Ammonium purpurate, the ammonium salt of purpuric acid, used as a complexometric indicator and a colorimetric reagent.
GNU Webster's 1913
- n. (Chem.) A crystalline nitrogenous substance (C8H8N6O6, 5-5'-nitrilodibarbituric acid monoammonium salt) having a splendid dichroism, being green by reflected light and garnet-red by transmitted light. It was formerly used in dyeing calico, and was obtained in a large quantities from guano. It is now synthesized from alloxan. Formerly called also
“When an alkaline solution of murexide is precipitated by an acid, a light shining powder results, called purpuric acid.”
“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.”
“All of these, however, being more or less soluble in water, and owing their colours to murexide, would be ill adapted for pigments.”
“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.”
“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.”
“The third group includes safflower, magenta, and murexide (light shades).”
“A special character of this dye (murexide) is the presence of mercury, the salts of which serve as mordants for fixing it, and may be detected by the ordinary reagents.”
“A little ammonia is then added, when the fine _purple_ murexide stain will be produced.”
“It is not there: I find not the least trace of murexide.”
“The problem is solved: the colouring-matter which has just formed is murexide; and consequently the powdery substance which filled the cells was none other than uric acid, or more precisely ammonium urate.”
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