What is "salad-oil"

Usage examples of "salad-oil".

And from it he began to produce bottles--little fat bottles containing powders, small and slender bottles containing coloured and white fluids, fluted blue bottles labeled Poison, bottles with round bodies and slender necks, large green-glass bottles, large white-glass bottles, bottles with glass stoppers and frosted labels, bottles with fine corks, bottles with bungs, bottles with wooden caps, wine bottles, salad-oil bottles--putting them in rows on the chiffonnier, on the mantel, on the table under the window, round the floor, on the bookshelf--everywhere.