614 



inconsiderable, since oil-cakes of various kinds are much used as food 

 for stock, and they are liable to be of inferior quality because of care- 

 lessness in their manufacture or storing. To the oil producer the 

 quality of the residue he sells for farmers' use is a minor matter. To 

 insure the making of the best oil-cake for feeding purposes and to avoid 

 deterioration of the product before using, a more thorough understand- 

 ing of the chemical changes of tbeir oily and fatty constituents is essen- 

 tial. One of the facts to be met is that in these changes, which are 

 manifest in rancidity and other objectionable ways, the action of fer- 

 ments is a i^rominent factor. 



The article contains an account of studies of pea-nut oil, both the 

 expressed oil and that in the nuts and the press cakes, with reference to 

 the acid equivalent (amount of free fatty acids), the iodine number, and 

 the saponification equivalent. Pea-nut oil consists principally of the 

 gl3"cerivies of palmitic, arachic, and hj^pogjeic acids. 



Acid equivalent. — The free fatty acids were determined by titrating a 

 solution of these materials in alcoholic ether (free from acid), with a 

 solution of alcoholic potassium hydroxide (one quarter to one half nor- 

 mal), using phenolphthalein as an indicator. The acid equivalent or 

 expression for the number of mg. of KOH required per gram of fat, was 

 determined for peanut oil expressed and extracted from both fresh and 

 old nuts and i)resscakes, and that from various sources. The varia- 

 tions in acid equivalent were, for the fat extracted or expressed from 

 pea-nuts, 1.5 to 32.3, and for that from pea-nut cake 18 to 166. The 

 more important points brought out by these determinations were, in 

 brief, as follows : The fat of some pea-nut cakes undergoes more rapid 

 changes than that of others, depending upon the nuts from which the 

 cake comes, the method and thoroughness of the extraction of the oil, 

 the manner of storing, etc. Press cake from which the oil has been 

 very thoroughly expressed does not keep as well, with regard to the 

 fat, as that containing more oil. It was noticeable throughout the 

 investigation that the cakes which contained the most free fatty acids 

 were low in fat content, as is illustrated by the following results: 



This leads the author to believe that a thorough expression of the fat 

 offers more favorable conditions for the formation or elaboration and 

 spread of the ferment ("probably organized ferments") which causes 

 the decomposition of the fats. It is thought this may be due to a more 

 extensive breaking up of the cellular structure or to the increased 



