There are several grades of palm oil in commerce, but in toilet soap making it is advisable to utilize only Lagos palm oil, which is the best grade. Where it is desired to maintain the color of the soap this oil produces, a small quantity of the lower or "brass" grade of palm oil may be used, as the soap made from the better grades of oil gradually bleaches and loses its orange yellow color.
Palm oil produces a crumbly soap which cannot readily be milled and is termed "short." When used with tallow and cocoanut oil, or 20 to 25 per cent. cocoanut oil, it produces a very satisfactory toilet soap. In the saponification of palm oil it is not advisable to combine it with tallow in the kettle, as the two do not readily mix.
Since the finished soap has conveyed to it the orange color of the oil, the oil is bleached before saponification. Oxidation readily destroys the coloring matter, while heat and light assist materially. The methods generally employed are by the use of oxygen developed by bichromates and hydrochloric acid and the direct bleaching through the agency of the oxygen of the air.
The chrome process of bleaching palm oil is more rapid and the oxygen thus derived being more active will bleach oils which air alone cannot. It depends upon the reaction:
Na_{ 2}Cr_{ 2}O_{ 7} + 8HCl = Cr_{ 2}Cl_{ 6} + 2NaCl + 7O.
in which the oxygen is the active principle. In practice it is found necessary to use an excess of acid over that theoretically indicated.
For the best results an oil should be chosen containing under 2 per cent. impurities and a low percentage of free fatty acids. Lagos oil is best adapted to these requirements. The oil is melted by open steam from a jet introduced through the bung, the melted oil and condensed water running to the store tank through two sieves (about 1/8 inch mesh) to remove the fibrous material and gross impurities. The oil thus obtained contains fine earthy and fibrous material and vegetable albuminous matter which should be removed, as far as possible, since chemicals are wasted in their oxidation and they retard the bleaching. This is best done by boiling the oil for one hour with wet steam and 10 per cent. solution of common salt (2 per cent. dry salt on weight of oil used) in a lead-lined or wooden tank. After settling over night the brine and impurities are removed by running from a cock at the bottom of the vat and the oil is run out into the bleaching tank through an oil cock, situated about seven inches from the bottom.
