The exhaust pipe extends into the atmosphere a short distance above the deodorizing tanks. On account of the extreme agitation caused by the heat, the oil is likely to boil over and waste. Special attention is called to the crook or neck in the exhaust pipe with two-inch outlet at the lowest point. This is done so that the condensation will not run back into the oil, but can be taken out at this point. =Process For Oil.=--The tank is filled with oil to about half its capacity. The oil is then heated to a temperature of 320° to 360° F. After being held at this temperature for an hour to an hour and a half, it is ready for the washing process. This is done by means of a two-inch perforated pipe at the top of the kettle, through which is sprinkled cold water on the oil. The extreme temperature evaporates the water very rapidly and at the same time causes a precipitation. The water should be allowed to run for five minutes, and then the body of oil should stand for from one to two hours. The cone, or bottom of the kettle, will be found to have a sediment which has been precipitated from the oil. This “bottom” should be drawn off, and the steam again turned on the coils. [Illustration: FIG. 155.--DEODORIZING TANK FOR COTTON SEED OILS.] _Blowing._--The oil is heated to the original temperature and steam of high pressure and temperature introduced into the body of the oil. The length of time required for treating the oil depends largely upon its nature, some oils being more neutral and more nearly odorless than others, consequently no exact rule can be laid down that would fit all cases; it must be left to the judgment of the person handling the oil. _Pressure and Temperature._--To obtain the temperature above mentioned a pressure of 150 pounds should be carried, and late practice introduces a superheater for reheating the steam to insure high temperature by adding 100° to 150° F. to the steam temperature. [Illustration: FIG. 156.--SECTION OF BOTTOM OF DEODORIZING TANK.] _Bleaching Process._--As soon as the oil is deodorized it is drawn off and allowed to cool. It is pumped into the treating kettle, or what is known in refineries as the “dirt” kettle. There it is brought up to a temperature of 160° F., when the fullers earth is added, generally using from one to two percent of earth with this bleach, following an agitation of about ten minutes. It should then be pumped through the filter press into the receiving tank, where it is held until used. After going through this process the oil is known to the trade as “water white.” [Illustration: FIG. 157.--SECTION THROUGH EXHAUST HOOD OF DEODORIZING TANK.] _Mixing._--Refined tallow or oleo stearine melted and clarified by pumping through a filter press without the use of fullers earth is added to the cotton seed oil so prepared, and the mixed substance, containing proportions previously described, are ready for passing over the cooling roll.