456 FOODS AND FOOD ADULTERANTS. 



are reweighed after the sample has been taken out and rim into a sa- 

 pouitieatiou bottle; 50 cc of the semi-normal potasli are added, tbe 

 bottle closed and placed in tbe steam-bath until the contents are en- 

 tirely saponified, facilitating tbe operation by occasional agitation. The 

 alcoholic potash is measured always in the same pipette, and uniformity 

 further insured by always allowing it to drain the same length of time, 

 viz, thirty seconds. Two or tbree blanks are also measured out at the 

 same time and treated in the same way. 



In from five to thirty minutes, according to the nature of the fat, the 

 liquid will appear perfectly homogeneous, and when this is the case the 

 saponiflcatiou is complete, and the bottle may be removed and cooled. 

 When sufficiently cool the stopper is removed and the contents of the 

 flask rinsed with a little 95 per cent, alcohol into an Erlenraeyer flask 

 of about 200 cc capacity, which is placed on the steam-bath, together 

 with the blanks, until the alcohol has evaporated. 



Titrate the blanks with semi-normal MCI, using phenolphthalein as 

 an indicator. Then run into each of the flasks containing the fat acids 

 1 cc. more semi normal HC1 than is required to neutralize to potash in 

 blanks. The flask is then connected with a condensing tube 3 feet 

 long, made of small glass tubing, and placed on the steam-bath until 

 the separated fatty acids form a clear stratum on the surface of the liq- 

 uid. The flask and contents are then allowed to become thoroughly 

 cold, ice-water being used for cooling. 



The fatty acids having quite solidified, the contents of the flask are 

 filtered through a dry filter paper into a liter flask, care being taken 

 not to break the cake. Two hundred to three hundred cubic centime- 

 ters of hot water is next poured on the contents of the flask, the cork 

 with its condenser tube re-inserted, and heated on the steam-bath until 

 the cake of acids is thoroughly melted, the flask being occasionally agi- 

 tated with a circular motion, so that none of its contents are brought on 

 the cork. When the fatty acids have again separated as an oily layer, 

 the flask and its contents are cooled in ice-water, and the liquid filtered 

 through the same filter into the same liter flask. This treatment with 

 hot water, followed by cooling and filtration of the wash- water, is re- 

 peated three times, the washings being added to the the first filtrate. 

 The mixed washings and filtrate are next made up to 1 liter, and 100 cc, 

 in duplicate, are taken and titrated with deci-normal NaOH. The volume 

 required is catenated to the liquid. The number so obtained represents 

 themeasure of deci-normal NaOH neutralized by the soluble fatty acids 

 of the butter fat taken, plus that corresponding to the excess of the 

 standard acid used, viz, 1 cc. The amount of soda employed for the 

 neutralization is to be diminished, for the 1 liter, by 5 cc, corresponding 

 to the excess of 1 cc % N. acid. 



This corrected volume, multiplied by the factor .0088, gives the buty- 

 ric acid in the weight of butter fat employed. (See table.) 



