EDIBLE FATS AND OILS. 143 



Weigh from 2 to 4 grams of the acetylated fats Into a flask and saponify 

 with alcoholic potash as In the determination of saponiflcation equivalent. If 

 the distillation process is to be adopted it is not necessary to work with a 

 standardized alcoholic potash solution, but in the filtration method, which is 

 much shorter, the alcoholic potash must be ^eft^vira^' exactly. In either case 

 evaporate the alcohol after saponification and dissolve the soap in water. Then 

 either- distil or filter avfoilows: 



(a) DISTILLATION. 



Acidify with dilute sulphuric acid (1 to 10) and distil as in the Reichert- 

 Meissl test (page 139). As several hundred cubic centimeters must be distilled, 

 either run a current of steam through or add portions of water from 

 time to time. From 500 to 700 cc of distillate will be sufficient Filter the 

 distillates to remove any insoluble acids carried over by the steam, and titrate 

 with tenth-normal potassium hydroxid, using phenolphthalein as indicator. 

 Multiply the number of cubic centimeters of alkali employed by 5.61 and 

 divide by the weight of substance used to obtain the acetyl value. 



(b) FILTRATION. 



Add to the soap solution a quantity of standard sulphuric acid exactly 

 corresponding to the amount of alcoholic potash added, warm gently, filter off 

 the free fatty acids which collect on top, wash with boiling water until the 

 washings are no longer acid, and titrate the filtrate with tenth-normal potassium 

 hydroxid, using phenolphthalein as indicator. Calculate the acetyl value as 

 directed under (a). 



14. Maumene Number, a Provisional. 



Place a beaker, 5 by 1.5 inches (12.7 by 3.8 cm) inside of another 6 by 3 

 inches (15.2 by 7.6 cm) and pack a wet mixture of asbestos and plaster of Paris 

 tightly around the inner beaker. This, when dried, makes a hard, solid packing 

 which radiates heat very slowly. 



Remove the inner beaker, weigh into it 50 grams of fat, and note the tem- 

 perature carefully. Then from a pipette which will deliver it in approximately 

 one minute add 10 cc of the strongest sulphuric acid which is at the same tem- 

 perature as the oil. Stir the oil and acid with an accurate thermometer while 

 the acid is being introduced, then hold the thermometer bulb carefully in the 

 center of the mixture, and when the mercury reaches the highest point note 

 the reading. It is easy to determine this point, as the column of mercury 

 remains stationary for some time. Do not read the temperature too soon, as 

 some oils take considerable time to reach their maximum point 



The difference between the initial and the final reading expressed in degrees 

 Centigrade is the Maumeng number. 



Great care must be taken to use acid of maximum strength. With the semi- 

 drying oils, such as cottonseed, the use of this strength of acid will cause 

 foaming and make it almost impossible to obtain the correct rise of temper- 

 ature. With such oils either a weaker acid must be used and the results 

 compared with the rise of temperature with water or a dilution with paraffin 

 oil is made. It is always best to test the apparatus and acid by use of water and 

 oils of known purity. In reporting results, the rise of temperature with water 

 should be stated, otherwise they possess no comparative value. 



a Allen, Commercial Organic Analysis, 3d ed., 2 (1) : 76. 



