OPERATION'. 



Weigh 50 grams of the fat into a metal dish. Measure 40 cc of caustic soda, 36 

 Baume, and 50 cc of 95 per cent alcohol into the small bottle. Heat the fat over a 

 gentle flame to 115 to 120 C. Shake the alcohol and soda solution well together 

 and add to the fat. Stir vigorously over a gentle fire until soap becomes sufficiently 

 dry to form pieces which will no longer adhere to the spatula by gentle pressure. 



Redissolve in 20 cc of alcohol and again dry to a condition in which the soap will 

 not adhere to the spatula by pressure. 



, Transfer the dry soap to the porcelain dish. Add 1 or 2 liters of boiling water and 

 keep the mixture boiling for 40 minutes. Replace, by adding cold water, about the 

 same quantity of water which has been evaporated by the previous boiling. Add to 

 the soap solution 70 cc of 25 Baume sulphuric acid. Boil again until the fatty 

 acids, which will float on top, are perfectly clear and transparent and show no signs 

 of any particle of soap which has not dissolved. Siphon off the acid water and trans- 

 fer the fatty acids to a small beaker, melt the acids, and allow the water to settle; 

 transfer to a dry beaker and dry in a water bath or on a steam bath for 20 minute** 

 and filter the fatty acids through white filter paper, using a hot-water funnel. 



Place the clear fatty acids in the titer tube, filling it two-thirds full, the tube being 

 first warmed in the water bath. Insert the tube in the perforated cork of the large 

 bottle, to serve as an air bath, and hang the delicate thermometer so that the bulb 

 will be exactly in the middle, in all directions, of the mass and allow the fatty acids 

 to cool until the mercury stops falling and just bey 'm* t rise again. Then move the 

 thermometer rapidly around the sides of the tube, three times to the right and three 

 times to the left, without any up or down motion, finally replacing the thermometer 

 in the center of the tube. 



Watch the thermometer as the mercury rises and take the highest point reached 

 as the titer test, at the same time recording the temperature of the room in which 

 the test was made. 



WOLFBAUER METHOD. 



Seventy-five grams of the fat are placed in an iron dish with 150 cc of caustic soda 

 lye of 13 per cent to 14 per cent strength. The mixture is boiled to dryness, with 

 constant stirring, so as to avoid scorching. In practice, a 3-pound lard pail is used, 

 instead of the iron dish, and a heavy stirring rod to break up the lumps. The dry 

 granular soap is then transferred to a porcelain dish of about 1,000 cc capacity in 

 which 500 cc of water and 250 cc of sulphuric acid of 60 per cent strength have been 

 previously mixed. The whole is boiled until the soap is decomposed, water being 

 added from time to time to maintain the original volume. An enameled cover is 

 kept on the dish while boiling. When the fatty acids are perfectly transparent they 

 are washed several times with boiling hot water, allowed to settle^ decanted, filtered 

 through several thicknesses of dry filter paper, and dried for four hours at 105 C. 

 The fatty acids when dried are cooled to about 15 or 20 C. above the expected 

 titer and transferred to a special tube 1 inch in diameter and 4 inches in length. 

 The tube is made of glass about -/+ of an inch thick. It is placed in a bottle fitted 

 with a cork, which is perforated so as to hold the tube rigidly when in position. 

 The thermometer, graduated to 0.1 C., is suspended so that it can be used as a 

 stirrer, and the mass is stirred slowly until the mercury remains stationary for at 

 least 30 seconds. The thermometer is then allowed to hang quietly, with the bulb 

 in the center of the mass, and the rise of the mercury is observed. The highest 

 point to which it rises is taken as the titer of the fatty acids. 

 The fatty acids should always be tested for complete saponification, as follows: 

 About 3"cc of the fatty acids are placed in a test tube and about 15 cc of strong 

 alcohol added, the mixture brought to a boil, and an equal volume of ammonia 

 (sp. gr. 0.96) is added. A clear solution should result, turbidity indicating presence 

 of unsaponified fat. 



It will be noted that the method differs from the Dalican test in two important 

 details. First, the fatty acids are thoroughly dried; second, the method gives a 

 definite time at which to stop stirring. The thorough drying of the fatty acids was 

 adopted as given above, as it has been clearly demonstrated that moisture in the 

 fatty acids lowers the titer about 0.4 to 0.5 C. Further, if the fatty acids are dried 

 in hydrogen gas by heating up to 150 C., the titer is the same as if the heating was 

 performed in the open air, or as if they were dried in a bath for four hours at 105 C. & 



. Lewkowitsch, Chemical Analysis of Oils, Fats and Waxes, 2d ed., p. 100. 

 &Ibid., Wolfbauer's work, pp. 134-135. 



