616 



from old and spoiled nuts, or which has been improperly stored, will 

 show a lower iodine number. The rancid condition of the fat is 

 expressed in a reduction of the iodine number. 



ISaponiJication. — In general it may be assumed that a fat will show a 

 high saponification equivalent the greater the changes it has under- 

 gone. The method used for determining this equivalent was as fol- 

 lows : After titrating the solution of fat in alcoholic ether to determine 

 the free tatty acids, an excess of potassium hydrate was added, and 

 the solution heated on a boiling water bath for an hour. An excess 

 of hydrochloric acid was added after the saponification, the solution 

 titrated back with standard alkali solution, using phenolphthalein as 

 indicator, and then strongly diluted with water to show that the sapou- 

 itication had been complete. The indications furnished by the deter- 

 mination of the saponification equivalent were not so pronounced and 

 stioug as those of the iodine number or acid equivalent. It is thought, 

 however, to be of use as an indicator in some cases, and is more rapidly 

 and easily carried out and requires less preparation than the iodine 

 absorption. 



Conclusions. — The conclusions from the above studies are given as 

 follows : 



The pea-nut oil is very changeable. The fresh oil is nearly colorless, 

 clear, thin, has a faint but pleasant odor and taste, and contains no 

 free fatty acids. The saponification equivalent is lowest and the iodine 

 number the highest in the fresh oil. The expressed oil changes only 

 slowly and slightly. When freely exposed to the light for a long 

 time it becomes thicii and rancid and shows then a lower iodine 

 number and a higher saponification equivalent, together with a slight 

 increase of the acid equivalent. 



The fat in pea-nuts changes very little with the age of the nut, in 

 case the outer shuck has not been broken; and the broken nuts show 

 only a low conteut of free fatty acids after lying for years. A notice- 

 able increase of ihe saponification equivalent and a decrease of the 

 iodine number occurs only with old and si)oiled nuts, which look bad 

 and have a rancid smell. The greatest changes occur in the lat of the 

 l^ea-nut cake, and this change reaches the maximum in cake containing 

 a low percentage of fat. The acid equivalent in particular increases 

 rapidly ; the iodine number may decrease one third, particularly when 

 old and spoiled nuts have been used, and in this case the saponifica- 

 tion equivalent is increased. 



For judging of the freshness of pea-nut cake (as indicated by the 

 reactions of the fat) the first indication is furnished by the appearance 

 of the extracted fat. If it is solid at ordinary temperature, large 

 quantities of free fatty acids are present, and in proportion as the i'at 

 contains less of these it is softer. The extraction is to be made with 

 gr» at care. The iodine number is the best indicator as to the fresh- 

 ness of peanut cake and the condition of materials from which it came. 



