MKTHHhs <>i ANALYSIS, 2v 



a number of samples of olive oil of known history. Nos. -J'JUIT, 

 J^Tl-1, and :^J1*JI all show an acidity that might be considered normal 

 for fresh oils, although eight and ten yeai-old. On the other hand 

 Nov. -J-JlHS and _'_'', 1 '.. which were three year^ and our year old. respee 

 tively. show an excessive amount of free acid. It therefore follows 

 that the time factor has but little influence upon t he acidity, while 

 No. J'JtJl!* indicates that high temperature favors the formation of the 

 free acids. 



X X. -/'/// ni-iih in u/ii-i' nifx. 



Eleven samples of pure California olive oils, all of which were con- 

 sidered fresh oils, o-ave an average content of free acid of 1.1' per 

 cent, and the extremes were 0.59 per cent and '2. "24 per cent. Twelve 

 samples of commercial California olive oils in which no added oil was 

 detected contained an average of iJ.40 per cent free acids, and this 

 figure is more nearly in accord with the averages of the French and 

 Italian commercial oils than is the average given for the California oiU 

 of known purity. This is undoubtedly due to the fact that previous to 

 leaving the storeroom of the manufacturer the oil is kept under more 

 favorable conditions of light and temperature than it receives after 

 entering the retail store>. 



By reference to Table XXXIII it is seen that lard oil, peanut oil. 

 and the various seed oils show an appreciable content of free acid*, 

 differing in this respect but little from olive oils. ( 'otton-seed oil alone 

 is an exception. This oil is refined by use of alkali, and so shows but 

 small amounts of acidity and vields but little upon long landing. 



The rancidity of oils and fat- has been the subject of extensive 

 study by various Investigators, and opinions regarding iN cau>e- are 

 extremely varied. Lewkowitsch" states that pure, nondrying oils 

 when protected from air and light remain unchanged at ordinary tem- 

 peratures: on exposure to light and air they undergo change, consist- 

 ing of the development of butyric. Lsobutylacetic, and other volatile 

 acids in small quantities, an increa.-e in free acids, and the acquire- 

 ment of a disagreeable smell and acrid taste. These change- the 

 author considers due to direct oxidation by the oxygen of the air. llnV 

 action being intensified by sunlight. 



"ClnMn. anal, oils, i'at>, ami waxes, lM !., 



