Paraffin oil is also sometimes detected by smell: pour a couple of drops on the palm of the hand, rub the two hands briskly together, when the characteristic smell of paraffin will be easily detected if any considerable amount be present. Turpentine is sometimes adulterated with rosin spirit, and this can only be detected by means of analysis.
Linseed Oil.
—To ascertain with absolute certainty whether a sample of linseed oil is pure or not is by no means easy, and can only be done by aid of chemistry. There are various methods by which the adulteration can be ascertained, but we hesitate to print them here, because they may prove misleading to the uninitiated. The experienced painter has two tests of his own, viz., smell and the working of the oil, and if these lead him to suppose it is adulterated his only safe plan is to obtain the services of a competent chemist.
We next reach a consideration of the different qualities of the principal pigments, and can best show these by means of tables.
PIGMENTS.
Some Useful Tables.
Pigments Liable to Change under the Influence of Sulphuretted Hydrogen, Air, and Moisture:
Yellow.—Turner’s yellow, chrome yellow, mineral yellow, Naples yellow.
White.—Cremintz white, flake white, pearl white.
Red.—Red lead, purple red, iodine scarlet.
Green.—Verdigris, Scheele’s green, emerald green, mountain green.