IMPROVED METHODS FOR FAT ANALYSIS. 99 



and fats have saponification numbers lying between 1S5 and 200, with a 

 mean of approximately 193. While the nmiibers for different products are 

 quite characteristic they are bj' no means fixed or constant, varying with 

 the state of purity and rancidity. The character of an oil or fat is affected 

 also by natural conditions, such as climate, soil, food supplj- and other 

 factors influencing formation or production, and by method of separation 

 or preparation. 



Fats and oils containing a considerable amount of the glycerides of the 

 lower (volatile) fatty acids and of myi-istin are characterized by a saponi- 

 fication number exceeding 200. Among the more prominent of these, 

 testing from 210 to 290, are croton oil, spindle tree oil, turtle, dolphin 

 jaw, porpoise jaw and brown fish of the blubber oils, several of the myris- 

 tica group, the coconut oil group including palm-nut, coconut and other 

 less common oils, the dika fat group, Japan wax and butter fat. Oils and 

 fats containing a considerable proportion of glycerides of the higher fatty 

 acids, particularly hydroxy acids, are characterized by low saponification 

 numbers. Castor oil, consisting largely of ricinolein, has a saponification 

 number of about 185. The rape oil group, including rape (colza) and 

 various mustard oils, have saponification numbers of about 175, on account 

 of the large proportion of erucin. 



Liquid and solid waxes, such as sperm oil, flax wax, wool wax, beeswax, 

 spermaceti, insect wax, etc., are characterized by extremely low saponifi- 

 cation numbers, from 80 to 140, due to the large proportion (nearly one- 

 half) of monobasic alcohols and of hydrocarbons. 



Monoglycerides, with only one acid radical, and diglycerides, with two, 

 have a lower saponification number than the corresponding triglycerides 

 with three acid radicals. 



Glycerides can also be hydrolyzed by concentrated mineral acids; by 

 superheated steam with a catalyzer such as hydrochloric acid or with an 

 accelerator such as caustic lime, potash or other oxide; by enzymes; by 

 sulfoaromatic compounds such as Twitchell reagent, etc. 



Acid Number. 



The acid number indicates the number of milUgrams of potassium 

 hydroxide required to neutralize the free fatty acids in 1 gram of an oil, 

 fat or wax. 



Reagents. — Alcohol: redistilled, free from acids and aldehydes. 



N/10 potassium (or sodium) hydroxide. 



Phenolphthalein solution: 1 gram to 100 cubic centimeters of alcohol, 

 neutralized. 



Cotton blue 6B solution: 2 grams to 100 cubic centimeters of alcohol. 

 The indicator should be boiled in a flask under a reflux condenser for two 

 hours and then filtered. 



Method. — Ten grams of fat are brought into a 300 cubic centimeter 

 Erlenmeyer flask, together with 100 cubic centimeters of alcohol and 

 several glass beads. The flask is connected with a spiral or other form of 



