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Symbol/formula: H2SO4
Sulphuric acid. A mineral acid composed of the elements sulphur, oxygen, and hydrogen.
Symbol/formula: O
Now known as oxygen. Oxygen is a colourless, odourless, tasteless gas essential to living organisms.
Produced when quicklime is mixed with water. Traditionally called slacked lime.
A translucent, colourless, flavorless food ingredient, commonly derived from collagen taken from animal body parts.
Isatis tinctoria. a yellow-flowered European plant of the cabbage family. It was formerly widely grown in Britain as a source of blue dye, which was extracted from the leaves after they had been dried, powdered, and fermented.
Paubrasilia echinata. A species of flowering plant in the legume family which yields a historically important red dye called brazilin, which oxidizes to brazilein.
Haematoxylum campechianum - a species of flowering tree which was of great economic importance from the 17th century to the 19th century, when it was commonly logged and exported to Europe for use in dyeing fabrics. Its extract was once used as a pH indicator which was brownish when neutral, turning yellow-red under acidic conditions and purple under alkaline ones.
Biiter and astringent compounds found in plants. They include Ellagic acid, gallic acid, and pyrogallic acid which were first discovered by Braconnot in 1831.