1 72 MILK AND DAIRY PRODUCTS PART 



as to cause the particles of solid acid floating on the surface to 

 adhere to the neck. After ten minutes' cooling the physical 

 condition of the fatty acids is observed, and it is noted whether 

 a solid or semi-solid opaque shapeless mass is present, or 

 whether there are clear drops of oil (cocoa-nut fat.) l 



After closing the neck of the flask with a glass stopper, the 

 distillate is mixed by inverting the flask four or five times, 

 after which the contents is filtered. The Reichert-Meissl 

 number of the filtrate is then determined in the usual manner. 

 The filter must have a diameter of 8 cm., and must fit close to 

 the sides of the funnel. 



After the distillate has completely filtered through, the filter 

 is washed three times with 15 c.c. water, the filter being filled 

 each time to the top. This wash water must first be used to 

 wash out thrice the condenser tube, the measuring cylinder and 

 the receiver. When all of the wash water, the last 10 c.c. of 

 which should be neutralised by one drop of N/1Q baryta water, 

 has filtered through, exactly the same operations are repeated 

 with neutral 90 per cent, alcohol, 15 c.c. being used each time. 



The fatty acids in the united alcoholic filtrates are then 

 titrated with N/IO baryta water, three drops of phenol phtha- 

 lein being used as indicator, and the number of cubic centi- 

 metres which are required gives the Polenske number. 



The standard numbers given by Polenske must not be 

 regarded as absolute. Hesse 2 has shown that considerable 

 variations can occur in the relation between the Reichert- 

 Meissl and Polenske numbers, although the latter is seldom 

 below and often above that given by Polenske himself. 



Llihrig 3 arid Siegfeld 4 have found that feeding with cocoa-nut 

 cake and still more so with beet leaves causes the Polenske 

 number to rise. It cannot, however, be denied that the 

 Polenske number gives very valuable information, even though 

 it does not always suffice to prove whether or not a butter is 

 adulterated with cocoa-nut fat. Mlintz and Coudon 5 published, 

 at about the same time as Polenske did, a method of detecting 



1 These drops of oil contain caprylic acid, which is characteristic of cocoa- 

 nut fat. 



2 Milchwirtfichaftliches Zentralblatt, Vol. I, No. 1, 1905. 



3 Zeitschrift fur Unter. d. Nahr.- und Genussmitlel, 1906, Vol. 11, p. 11. 



4 Ibid., 1909, Vol. XVII, p. 177 ; Chemiker-Zeitung, 1907, No. 40. 



5 Bull, mensuel de V Office de remeignements agricoles, Fevr. 1904, p. 147. 



