Scientific American 7, 6.11.1847
Boil four parts of nitric acid on one part of indigo: the solution becomes yellow, and a resinous matter appears on the surface. Stop the boiling; let it cool: remove the resinous matter, and gently evaporate the solution to the consistency of honey. Re-dissolve it in hot water: filter; a solution of potash will throw down yellow spicular crystals coasisting of bitter principle, combined with potash. These crystals have the curious power of detonating with a purple light when wrapped in paper and struck by the hammer. The resin by being treated again with nitric acid, is converted into the same bitter principle.
Coloriasto on väriaiheisten tekstien (ja kuvien) verkkoarkisto
(Archive for colour themed articles and images)
INDEX: coloriasto.net
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