【文章內(nèi)容簡介】 rovement is shown by the fact that tallow is here included in the group that is quite easily saponifled while cottonseed oil and hydrogenated cottonseed oil remain in the group that is difficult to saponify. We believe the reason for its improved success is the intimate mixing caused by the mechanical stirring which liberates the oil particles occluded by the soap formed in the initial reaction. The emulsion is very stable in the 105 176。 C. oven in which the saponification takes place. Again the excess potassium hydroxide is small. With greater excess there is a tendency for the soap when formed to salt out, thereby causing the emulsion of the oil and aqueous caustic solution to break down. III. The Method Involving the Use of a Carius Tube The idea was suggested in our laboratory that the saponification operation be made in a Carius tube. In this method, 5 grams of fat or oil is placed in a Carius tube, 50% potassium hydroxide solution added (3 cc. for tallows and palm oils and 4 cc. for coconut oils), and the Carius tube heated in a steam bath to melt any oil which may have spattered on the wall of the tube when it was introduced. Twentyfive cc. of distilled water are added, washing down the walls of the tube, which is then sealed and annealed, thoroughly shaken and heated overnight in the Carius oven at 130135 176。 C. The oxidation is done by means of potassium dichromate, the excess of which is titrated with sodium thiosulphate solution using starch as the indicator. Results by this method pared with those of Method I as well as those determined from the ester values are given in Table II. It will be seen that in the first four cases the results of Method I and the Carius Method agree very well, but both vary from the percentage glycerol determined from the ester value. The variation is greater for the acidulated oils than for the unrefined oils, a fact which is in agreement with laboratory experience. Method I is not applicable to such oils as refined tallow, but it will be noted in these cases that the results of the Carius Method agree very well with those calculated from the ester values. This work was extended to the refined and pure oils, the results of which are given in Table III. After this set of experiments was pleted it was found that coconut oil requires a lower temperature than the other oils, and probably if the effect of temperature were studied, a condition for plete saponification could be ascertained. The averages of several determinations for Cottonseed oil, hydrogenated cottonseed oil, and tallow vary +, +, and + percent, respectively, from the calculated values obtained from the saponification and acid numbers, while the greatest deviation of a single determination differed from t39。he theoretical value by +, +, and + percent, respectively. These deviations are greater than is desirable. It may be that by improved methods of oxidation and titration greater accuracy may be obtained. The potassium hydroxide attacks the glass of the Carius tube during the prolonged heating and when the sulphuric acid is added in excess to convert the soap to fatty acids, silicic acid is precipitated. When the excess sulphuric acid is neutralized with sodium hydroxide the silica causes a fugitive end point and may possibly be responsible for the high results noted. The etchings on the inside of the Carius tube are of such appearance as to raise considerable doubt as to just when all the soap jell and glycerol has been washed out. More work should be done on this method as it seems to offer possibilities IV. The Catalytic Method The use of ccnaphthol, flnaphthol, and thymoP as catalysts in saponification has been described and increased efficiency demonstrated. It has been stated that bentonite 5 is probably the most active and generally useful catalyst for this purpose. The use of a catalyst, which in this case is actually an emulsifying agent was thus suggested for laboratory saponification. A. Stearic Acid On the basis of easy saponification of oils containing free fatty acids, small quantities of steark acid were added to refined and purified fats when these were to be saponified and the percentage of glycerol determined, and it was found that oils which could not be saponified by the direct method were then readily saponified. Conditions and amounts of stearic acid and 50% potassium hydroxide were varied to determine those most satisfactory for plete saponification of an oil of the hardened cottonseed type, which we shall designate as Oil A. The quantity of potassium hydroxide was first varied from 4 to 8 ㏄ . to determine which gave the best emulsion. The data are given in Table IV. On the basis of this and similar experiments, 4 cc. of 50% aqueous potassium hydroxide was chosen as standard From experience it was known that for this particular Oil A, the best emulsion resulted when the potassium hydroxide was added to the oil which was heated to a temperature of 140150 176。 C. However, to asc