Analysis.
SAMPLE.
The sample must be representative and at least three pounds in weight and taken in accordance with the standard methods for the sampling of commercial fats and oils. It must be kept in an air-tight container, in a dark, cool place.
Soften the sample if necessary by means of a gentle heat, taking care not to melt it. When sufficiently softened, mix the sample thoroughly by means of a mechanical egg beater or other equally effective mechanical mixer.
MOISTURE AND VOLATILE MATTER.
Apparatus: Vacuum Oven—The Committee Standard Oven.
Description—The Standard F. A. C. Vacuum Oven has been designed with the idea of affording a simple and compact vacuum oven which will give as uniform temperatures as possible on the shelf. As the figure shows, it consists of an iron casting of rectangular sections with hinged front door made tight by means of a gasket and which can be lowered on opening the oven so as to form a shelf on which samples may be rested. The oven contains but one shelf which is heated from above as well as below by means of resistance coils. Several thermometer holes are provided in order to ascertain definitely the temperature at different points on the shelf. In a vacuum oven where the heating is done almost entirely by radiation it is difficult to maintain uniform temperatures at all points, but the F. A. C. oven accomplishes this rather better than most vacuum ovens. Larger ovens containing more than one shelf have been tried by the Committee, but have been found to be lacking in temperature uniformity and means of control. The entire oven is supported by means of a 4-in. standard pipe which screws into the base of the oven and which in turn is supported by being screwed into a blind flange of suitable diameter which rests on the floor or work table.
Moisture Dish—A shallow, glass dish, lipped, beaker form, approximately 6 to 7 cm. diameter and 4 cm. deep, shall be standard.
Determination—Weigh out 5 grams (= 0.2 g. of the prepared sample) into a moisture dish. Dry to constant weight in vacuo at a uniform temperature, not less than 15° C. nor more than 20° C. above the boiling point of water at the working pressure, which must not exceed 100 mm. of mercury.[25] Constant weight is attained when successive dryings for 1-hr. periods show an additional loss of not more that 0.05 per cent. Report loss in weight as moisture and volatile matter.[26]
