A Manual of the Chemistry of the Carbon Compounds

THE CARBON COMPOUNDS. 245
NH—CO NH—CO
CO CRNHa + CHOH - CO 0H.NH.CO.NH,
NH—CO NH—CO
Snfylw-pseudo-wic Acid C6H6N4O8S is produced by heating alloxan
and sulphur-urea with a concentrated alcobolic solution of sulphur
dioxide;—
NH—CO NH—CO
CO CO + NHg.CS.NHj - CO C.H.NH.CS.NHS + 0
NH—CO NH—CO
It forms thin white needles and is insoluble in mter, but soluble
in acids,
Pwrpwic Acid CgHgN^Oj.—-This compound is not known in the
free state; its ammonium salt is that beautiful substance] known by
the name of murexide, which is obtained by boiling a mixture of
dialimunide and mercuric oxide with dilute aqueous ammonia. It
may also be prepared by adding ammonia to a hot solution of
dialuramide and alloxan:—
NH8 + C,H6N8Oa + C4H2FaO4 = CSH5NBO7,NHS + HaO
Murexide is also formed by evaporating uric acid with a little nitrio
acid nearly to dryness, and adding ammonia to the residue.
Murexide crystallizes in small prisms, which by reflected bght
exhibit a fine beetle-green lustre, and dissolve in water with an
intense purple colour. The solution dyes silk and wool a beautiful
red shade, and was a few years ago manufactured foi this purpose,
but has now been superseded by aniline-red.
When, & solution of murexide is boiled with, potassium nitrate,
potassium purpufate C^L^fi^K, is formed, a salt resembling
murexide. The purpurates of the alkali-metals dissolve in water
with a bluish-purple colour; those of the other metals ore insoluble
in water. They are decomposed by acids with the formation of
dialuramide and alloxan.
Purpuric acid has probably the following constitution;—
NH—CO CO-NH
CO C=N—OH CO
NH—CO CO—NH
Hydurilic Acid C8H4H4O0.—When dialuric acid is healed with
glycerin it is resolved into carbon dioxide, formic acid, and acid