204 BUTTER 



number of c.c. required by the flask to which the butter 

 was added, and the amount of alkali required for the 

 saponification then calculated from a knowledge of the 

 strength of the alcoholic-potash solution. The weight 

 in milligrams of caustic potash required to saponify 

 I gram of butter is then given as the Koettstorfer 

 number of the sample of butter employed. 



194. The Unsaturated Acids in Butter-fat. 



While most of the acids present as glycerides in 

 butter are saturated and contain no double or triple 

 bonds, there are, however, always present a certain 

 small proportion of unsaturated acids, notably oleic, 

 and for this reason butter-fat will show a certain 

 absorption for iodine, generally to the extent of 25 to 

 50 per cent. It is usual in butter examination to 

 determine the iodine value, as valuable indication may 

 be thus afforded as to whether the butter has been 

 adulterated with any fats or oils which show a higher 

 iodine absorption. 



Hiibl's method, described in 13, p. 22, may be 

 employed on 0-5 gram of butter, following out the 

 details given ; but Wijs' method is more modern, and 

 possesses certain notable advantages over the older 

 method with regard to constancy of results and quick- 

 ness of determination. 



195. Determination of the Iodine Value by Wijs' 



Method. 



In this process the iodine is employed in the form 

 of iodine chloride (ICl). 



Iodine Chloride Reagent. — 9-4 grams of iodine 

 trichloride are weighed into a flask of about 300 c.c. 

 capacity, into which is then poured about 200 c.c. of 

 glacial acetic acid ; the flask, fitted with a cork through 



