252 THE ANALYSIS OF BUTTER FAT. 



is obtained by difference: from this is subtracted 0'4 to allow 

 for a blank, and the corrected figure is represented by T. 



To the measuring flask containing the neutral soap is now 



N N 



added a volume of -r H 2 S0 4 equal to that of NaOH required 



to neutralise the total volatile acids (T + 0'4), and after this are 

 added 61 grammes of pure dry sodium chloride (the salt used 

 should be neutral to phenol-phthalein, otherwise a slight correction 

 will be necessary). The flask is corked and well shaken to 

 dissolve the salt, the volume being made up to 200 c.c. The 

 contents of the flask are next filtered, and 190 c.c. of the filtrate 



N 

 titrated with NaOH : no further indicator need be added, as 



phenol-phthalein is already present. 



The number of c.c. of ^ NaOH required is multiplied by 



ID iy 



and from this is subtracted 0'4 for a blank. The number obtained 

 represents the soluble volatile acids, and is indicated by S. T S 

 gives the number I, which represents the insoluble volatile acids. 

 Variations for butter, coconut, and palm-kernel fats : 



BUTTEB FAT. 



T. From 26 "0 to 33 '0 

 S. 20-0 23-5 

 I. 5-0 9-5 



COCONUT FAT. 

 T. From 19'5 to 22'5 



PALM-KERNEL FAT. 

 T. From 12-0 to 14'0 



S. 1-3 1-8 I S. 1-0 1-3 

 I. 18-0 20-7 J I. 11-0 12-7 



Using average figures for pure butter, coconut, and palm-kernel 

 fats, the following three equations have been worked out, from 

 which can be calculated directly the percentage of any one of the 

 fats present in a mixture : 



(1) Per cent, butter fat = 4/67 S 0'35 I = x. 



(2) Per cent, coconut fat = 5 I 0'38z. 



(3) Per cent, palm-kernel fat = 7'69 I 0'59cc. 



Should butter fat be absent from the mixture the second terms 

 of the equations (2) and (3) vanish. 



It must be established by other methods whether coconut or 

 palm-kernel fats have been used. 



The method is rapid, a determination being completed in one 

 hour. 



Paal and Amberger distil the fatty acids from 2-5 grammes 

 of butter in steam in a special apparatus, collect 200 c.c. of dis- 

 tillate in from 35 to 40 minutes, wash out the condenser by 

 distilling 50 c.c. of neutral alcohol. The combined distillates 

 are neutralised, and evaporated, made up to 50 c.c., and 2 to 



