Commercial boiled oil is an uncertain quantity. We know of no satisfactory chemical or mechanical tests that determine its quality. Experiment and observation have taught us that no treatment of flax-seed oil improves it like storage and repose in tanks under favorable conditions. Under unfavorable atmospheric conditions, raw oil in paint may be made to dry better and more rapidly than boiled oil. When blended with a japan or siccative of the right kind, well-settled raw oil dries simultaneously throughout. Boiled oil dries on the surface first, and therefore is more apt to crack. A fair quality of boiled oil is preferable to raw oil made from unripe or impure flaxseed, or to raw oil improperly treated.

Linseed Oil Substitutes.—None of the standard  literature  upon oils recognizes any