almost colorless. Where cottonseed oil is used for mixing with lard it is highly important that it be practically free of color. When, however, it is used for mixing with oleomargarine the more yellow it is the more highly prized.
Extraction of Oil by Means of Petroleum.—The light oils which are produced in the refining of petroleum and commonly called gasoline are typical solvents for fat and oil. Instead of extracting the oil by the pressure process, as described above, a practically complete extraction may be secured by successive treatments with the light petroleum oils. The principle of the process is exactly that of the extraction of sugar from sugar beets by hot water in the process of the manufacture of beet sugar. The cottonseed cake or pressed meal is broken into fragments of approximate size, placed in tanks, and treated with successive portions of light petroleum. The extraction is arranged in such a way as to be a continuous one, that is, the vessels for handling the oil cakes are arranged en batterie as in the case of beet sugar extraction. By this method all except a mere trace of the oil is extracted from the cake. The light petroleum oils are subsequently separated from the cottonseed oil by distillation and are used again in the process. There is little loss of petroleum oil. Where cottonseed oil is used for technical purposes there is no objection to this method of extraction, and much is to be said in its favor since greater yields of oil are secured. When used for edible purposes, however, petroleum extracted cottonseed oil is not of as high a quality as that extracted by pressure. It is difficult to remove all traces of petroleum, especially the odor, and there are constituents extracted by petroleum which are not mixed with the oil when it is separated by pressure. It is advisable, therefore, that cottonseed oil used for edible purposes be cold-press extracted and not petroleum extracted oil.
Standard for Cottonseed Oil.—The official standards for cottonseed oil are as follows:
"Cottonseed oil is the oil obtained from the seeds of cotton plants (Gossypium hirsutum L., G. Barbadense L., or G. herbaceum L.) and subjected to the usual refining processes; it is free from rancidity; has a refractive index (25 degrees C.) not less than one and forty-seven hundred ten-thousandths (1.4700) and not exceeding one and forty-seven and twenty-five ten-thousandths (1.4725); and an iodin number not less than one hundred and f{our (104) and not exceeding one hundred and ten (110).
"'Winter-yellow' cottonseed oil is expressed cottonseed oil from which a portion of the stearin has been separated by chilling and pressure."
Hazelnut Oil.—The oil of the hazelnut is to a limited extent used for edible purposes. It is extracted from the seed of the hazelnut tree (Corylus avellana L). The seeds are very rich in oil and are said to contain from 50 to 60 percent thereof. The oil is almost free of stearin and is said to contain only about one percent. The rest of it consists chiefly of olein, there being but 12 percent of palmitin. While it is an edible oil, it is used chiefly in the manufacture
