If the market price of oleo stearine is high, a formula may be substituted as follows: 75 per cent cotton seed oil, 7¹⁄₂ percent tallow, 17¹⁄₂ per cent oleo stearine. In cold weather even a smaller amount of stearine may be used and a proportionately larger amount of tallow.
Cottonseed Oil.
—This is a product derived from cotton seed. Before the manufacture of cotton seed oil, the cotton seed, removed from the cotton, was thrown in large compost heaps and after decomposition, was used sparingly as a fertilizer. An idea of its value may be gained from the following table. From one ton of seed, by average, is obtained:
| 270 | pounds or 36 gallons of oil at 28c per gallon | $10.08 |
| 750 | pounds cotton seed meal at 90c per 100 pounds | 6.75 |
| 850 | pounds hulls at 15c per 100 pounds | 1.27 |
| 30 | pounds lint at 3¹⁄₂c | 1.05 |
| Total value | $19.15 | |
| 100 pounds waste and dirt. | ||
The oil when extracted from the seed is termed “crude oil.” In refining this oil the loss varies from 7 per cent to 12 per cent, on an average about 9¹⁄₄ per cent.
Refining Crude Oil.
—The crude oil is purchased by refiners and treated to produce “yellow oil.” In this process it is put into a tank (it is generally considered profitable to refine cotton seed oil only in large quantities) supplied with a revolving agitator. Into the tank is put a solution of eighteen to twenty per cent caustic soda. The quantity and strength of the solution necessary is determined by treating a small sample. To a small sample of oil add the soda solution, stirring continuously, having it heated to a temperature of 160° to 180° F. When sufficient soda lye has been added a floculent precipitation will be noticed. This indicates a “breaking” of the oil. By calculation of the relative amount the comparative quantities can be arrived at.
An excessive amount of lye will saponify its equivalent in good oil, therefore care must be exercised to see that only the proper amount is used. In a practical way the soda is introduced in the crude oil solution and agitation is started to insure the thorough mixing of the caustic soda and the oil. The floculent substance appearing, the agitation is stopped and the oil allowed to settle, the sediment and substance other than oil collecting at the bottom of the tank. A small quantity (about one-quarter of one per cent by weight) of fullers earth is added and the oil removed by pumping through a filter press producing what is known to the trade as “yellow oil.”
The sediment, known as “foots” is collected in kettles and treated with additional lye, boiled and settled with salt; water added, settled and drawn. This treatment is duplicated as many times as necessary, until the soap stock will separate from impurities. When thoroughly settled draw the soap stock into packages for the soap trade. The finished “foots” contains about 33 to 40 per cent of moisture and a small percentage of lye.