MILK FATS 33 



38. Saponification of Fats. When certain chemi- 

 cals, known as alkalies, such as potash and soda, are 

 heated with fat, they form soap ; the process is 

 called saponification. When saponification takes 

 place, part of the alkali unites with the fatty acid 

 of the fat and forms soap, while the glycerine radical 

 of the fat unites with the remainder of the alkali 

 and forms glycerine. 



39. Iodine Absorption of Butter Fats. In common 

 with other fats, butter fats have the property of 

 absorbing a definite amount of iodine. The iodine 

 number of butter, or the percentage of iodine ab- 

 sorbed by the fats, ranges from 28 to 35, while lard, 

 tallow, cotton-seed oil, and other commercial fats 

 and oils generally, have a greater capacity to absorb 

 iodine and hence have a higher iodine absorption 

 number. The iodine absorption number is fre- 

 quently used as an aid in detecting adulterated 

 samples of butter. 



40. Volatile Fatty Acids of Butter. When butter 

 fats are saponified and free fatty acids are liberated, 

 about 8 per cent of the volatile fatty acids are also 

 liberated and are volatilized in a current of steam. 

 In the analysis of butter, the amount of volatile 

 fatty acids obtained from 5 gm. usually requires 

 from 27 to 28 cc. of a tenth normal solution 

 of alkali for neutralization ; this is known as the 

 Reichert-Meissel value of butter, and is extensively 

 used in detecting adulterated butter. Spurious sam- 

 ples, as oleomargarine and butterine, have a low 



