Red of Sorghum.

Scientific American 5, 28.7.1866

It is a fact long known, that sorghum contains a red coloring-matter. The following is the process used by Mr. Winter to extract it: -

The canes of the sorghum are stripped of their leaves and reduced to a pulp in a rolling mill, and well pressed, to extract the juice from them. The juice is used to make sugar or alcohol. The ligneous tissue soon begins to ferment rapidly. Case must be observed to prevent too rapid fermentation, because by an elevation of temperature, the mass will become putrid. When the operation has well proceeded, and the mass, after fifteen days, has acquired a red or brown color, stop the fermentation by drying and grind the matter to divide it.

To isolate the coloring matter, infuse the powder for twelve jours in cold water, which dissolves a little coloring proerty. Press the mass strongly and put it to macerate with a very weak caustic lye, filter, press, and saturate the liquors with sulphuric acid. The coloring matter is separated in red flakes, which are collected on a filter, washed, and dried. This color is nearly pure, very soluble in alcohol, alkalies, weak acids, etc.

To dye silk and wool with it, use the ordinary tin mordant. Mr. Winter has noticed that the dyes made with this red resist the action of light, and a moderate bath of hot soap. The extraction and uses of this coloring matter are known and practiced in China, where sorghum is cultivated on a large scale.

- Bulletin de la Soc. d'encour