14 OLIVE OIL AND ITS SUBSTITUTES. 



The readings were made as near 15.5- ( 1 . as possible and correction I'm 

 temperature made by the following formula: 



G=G'+0.00003 (T-ir>.5 C.). 

 G = specific gravity at 15.5 C. 

 G'= specific gravit} 7 at T. 

 i. 00063 = mean correction for 1 C. (for olive oil). 



The correction factors for other oils are given in the provisional 

 methods for the analysis of foods. 6 



The determination of specific gravity is a quick way of detecting 

 gross adulteration of olive oil with the seed oils, practically all of 

 which have a higher specific gravity. The range of specific gravities 

 on pure olive oils of the grade used for salad purposes is quite narrow. 

 On 33 samples of pure California oils the specific gravity varied from 

 0.9162 to 0.9180, with an average of 0.9168. One sample, No. 673, 

 had a specific gravity of 0.9149, but had 12.11 per cent of free acid, 

 which explains the low gravity and excludes the oil from use for salad 

 purposes. Eighteen samples of Italian oils gave a range of from 

 0.9155 to 0.9180, with an average of 0.9163. Blasdale' on 11 sam- 

 ples of California oils found a variation of from 0.9161 to 0.9174:. 

 Milliard found on French oils a range of from 0.9169 to 0.9172, and 

 for Tunis oils* a range of from 0.9170 to 0.9196, with an average on 

 4l samples of o. 1)183. De Negri and Fabris- ; in a very exhaustive exam- 

 ination of Italian oils found on 7<> samples a range of from 0.91t>(> to 

 0.91 N i. and an average of O.JUWJ. These authors found one sampleof 

 oil made from rotten olives which had a specific gravity of 0.9145. 

 This low figure was most likely due to the presence of free fatty acids, 

 which were not determined, but which were probably present in suffi- 

 cient amounts to materially influence this constant and to exclude the 

 product from edible oils. Colby ( J gives the range for California oils 

 of (>.!! 40 to 0.9185, but in the absence of definite data regarding 

 the amount of free acids present the lower limit can hardly be accepted 

 for a normal oil. From the above figures it is apparent that there is 

 but little variation in the specific, gravity of edible olive oils from dif- 

 ferent sources and from different varieties of olives. 



The specific gravity of California, French, and Italian olive oils 

 varies from 0.9140 to 0.9185, while the oils from Algeria range as 



Allen, Com. Org. Anal., :!! <<!.. \>l. i'. p. I. j.. :;:;. Winton, Connecticut Agr. 

 K\).t. Sta. K.-pt., I'.KM), |.t. 1'. p. 149. 



&U. S. Dcpt. Agr., P.mvaii < .f ( 'lirmi>l ry Mill. !>",, p. L'l. 



.lour. Ai.irr. ('hnn. BOC., IS'.:>, 17: 086, 



Mini, du Ministrn- .! I 1 Agriniltuiv, ls'..\ j,. 1IJ9. 



''Milliau, Mertainchand ct Mah-t, Mill. <! I' Agrirultmv <-t ('oininrrrr <!< Tunis, 

 "Rapport sur lea huiles d'olivr <lr Tnnisir, l'.m." 



/AnnalidelLab. .-him. r.-ntr. delle Gabelle, v..l. 1. (ili (Hii. pi. 1, p. :',s. 



{/California Agr. p:xpt. Sta. i:-j.t.. 1SU7-98, p. li>. 



