Obs. Great care must be taken, in conducting the last process, not to employ too much heat, nor to allow the saline matter to stand long over the newly formed chrome-red, as the colour is thus apt to change to a brown or orange. When well managed the product has a crystalline texture, and so beautiful a red colour that it vies with native cinnabar. The liquid poured from the crucible is reserved for manufacturing chrome yellow.
Red, In′dian. Syn. Purple ochre; Ochra purpurea Persica, Terra Persica, L. This is a native production, brought from Ormus. A factitious article is prepared by calcining a mixture of colcothar and red ochre.
Lakes (Various).
Red, Light. From yellow ochre, by careful calcination. It works well with both oil and water, and produces an admirable flesh-colour by admixture with pure white. All the ochres, both red and yellow, are darkened by heat.
Red Or′ange. Syn. Sandix. Obtained from white lead by calcination. Very bright.
Real′gar. Bisulphide of arsenic.
Red Bole. See Armenian and Venetian bole. (Ochres.)
Red Chalk. A clay iron ore, much used for pencils and crayons, and, when ground, also for paints.
Red Lead. Syn. Minium. The finest red lead is prepared by exposing ground and elutriated massicott, or dross of lend, in shallow iron trays (about 12 inches square, and about 4 or 5 inches deep), piled up on the hearth of a reverberatory furnace, to a heat of about 600 to 650° Fahr., with occasional stirring, until it acquires the proper colour. The furnace employed for the preparation of massicot during the day usually possesses sufficient residuary heat during the night for this process, by which fuel is saved. Lead for the above purpose should be quite free from copper and iron.
Red O′chre. A natural product abounding on the Mendip hills.