The method of procedure for acid saponification, therefore, is to first purify the fats with dilute acid as already described. The purified, hot or warm, dry fat is then run to a specially-built acidifier or a lead-lined tank and from 4 per cent. to 6 per cent. of concentrated sulfuric acid added to the fat, depending upon its character, the degree of saponification required, temperature and time of saponification. A temperature of 110 degrees C. is maintained and the mass mixed from four to six hours. The tank is then allowed to settle out the tar formed during the saponification, and the fatty acids run off to another tank and boiled up about three times with one-third the amount of water. The water thus obtained contains the glycerine, and after neutralization is concentrated. AQUEOUS SAPONIFICATION. While lime or a similar substance is ordinarily used to aid in splitting fats in an autoclave, the old water process is still used. This is a convenient, though slower and more dangerous method, of producing the hydrolysis of the glyceride, as well as the simplest in that fatty acids and glycerine in a water solution are obtained. The method consists in merely charging the autoclave with fats and adding about 30 per cent. to 40 per cent. of their weight of water, depending on the amount of free fatty acid and subjecting the charge to a pressure of 150 to 300 pounds, until the splitting has taken place. This is a much higher pressure than when lime is used and therefore a very strong autoclave is required. Since fatty acids and pure glycerine water are obtained no subsequent treatment of the finished charge is necessary except separating the glycerine water and giving the fatty acids a wash with water to remove all the glycerine from them. SPLITTING FATS WITH FERMENTS. In discussing the causes of rancidity of oils and fats it was pointed out that the initial splitting of these is due to enzymes, organized ferments. In the seeds of the castor oil plant, especially in the protoplasm of the seed, the enzyme which has the property of causing hydrolysis of the glycerides is found. The ferment from the seeds of the castor oil plant is now extracted and used upon a commercial basis for splitting fats. The equipment necessary to carry out this method of saponification is a round, iron, lead-lined tank with a conical bottom, preferably about twice as long as it is wide. Open and closed steam coils are also necessary in the tank.