244: THE ANALYSIS OF BUTTER FAT. 



(5) Error due to the shape an.d size of the distilling vessel 

 and to the time of distillation (may vary the results ^ 5 per 

 cent.). 



To avoid these errors he lays down the following method of 

 working : 



Five grammes of butter fat are weighed into a round flask of 

 about 300 c.c. capacity, with a neck 2 cm. wide and 7 to 8 cm. 

 long ; 2 c.c. of a 50 per cent, soda solution and 10 c.c. of 96 per 

 cent, alcohol are added, and the flask heated for half an hour on 

 the water-bath under a slanting inverted condenser ; between 

 the latter and the flask is a T piece, which is closed, the limb 

 being turned upwards. At the expiration of half an hour the 

 limb of the T piece is opened and turned downwards, and the 

 alcohol distilled off during a quarter of an hour ; 100 c.c. of 

 boiling water are added by the T piece, and the flask heated on 

 the water-bath till the soap is dissolved. The solution is allowed 

 to cool to 50 or 60, 40 c.c. of dilute sulphuric acid (25 c.c. to 

 a litre ; 2 c.c. of soda solution should neutralise about 35 c.c. 

 of this) and two pieces of pumice the size of peas are added. 

 The flask is at once furnished with a cork carrying a tube 0-7 cm. 

 in diameter having, 5 cm. above the cork, a bulb 5 cm. in 

 diameter ; above this the tube is bent at an angle of 120, and 

 5 cm. further on again at an angle of 120 ; this tube is joined to 

 a condenser by an india-rubber tube. The flask is heated by a 

 very small flame till the fatty acids are all melted, and the flame 

 is then turned up and 110 c.c. distilled off in from twenty-eight 

 to thirty-two minutes. The distillate is mixed well, and 100 c.c. 

 are filtered off through a dry filter, 1 c.c. of a 0-5 per cent, 

 solution of phenol-phthalein solution in 50 per cent, alcohol 



N 

 added, and the solution titrated with ^ baryta solution. To 



the figure thus obtained one-tenth is added, and the amount 

 found by a blank experiment subtracted ; the blank should not 

 exceed 0-33 c.c. 



In order to render this method more sensitive, if possible, for 

 the detection of small quantities of butter in margarine, Hehner 

 proposed the use of 5 c.c. only of alcohol, saponifying (almost 

 instantaneously) in a closed flask, warming for five minutes with 

 occasional shaking, and driving off the alcohol through a narrow 

 tube in a cork, reduced pressure being applied towards the end, 

 and the addition of 100 c.c. of water which has boiled at least 

 half an hour. He finds the blank figure thus to be less than 

 O'l c.c., and the same as that given by 100 c.c. of boiled water 

 filtered through a dry filter ; other fats and oils give less than 

 0-06 c.c., and no increase is observed in heating them on the 

 water-bath with soda solution for two hours. 



