372 



The World's Commercial Products 



>t 



maize grain (see pp. 51-2). These 

 yield about thirty-five per cent, of 

 a fairly thick, light yellow oil used 

 for the same purposes as cotton 

 seed oil. 



NON-DRYING OILS 



Olive Oil. The geographical 

 distribution and characteristics of 

 the olive tree (Olea europaea, have 

 been described on p. 276. The 

 olive flowers in North Africa, in 

 Italy, and the South of Spain in 

 March or April ; the fruits mature 

 in about eight months, and the 

 principal harvest falls in the 

 months of December and January, 

 or later. It is extremely impor- 

 tant to gather the fruit when just 

 ripe, as at this stage it contains 

 the largest amount of oil, To 

 obtain oil of the finest quality, not 

 only should the olives be picked 

 by hand, but the oil should be 

 expressed within a day or two 

 after picking. In addition to the 

 oil contained in the fruit or 

 pericarp, the seeds also contain a 

 certain proportion of oil. 



The fruits are generally crushed 

 entire in an edge-runner mill or in 

 a roller mill, although the finest 

 oil is obtained by crushing the 

 flesh alone, when the fruit is 

 reduced to a pulp or "marc." 

 The marc is packed in circular 

 baskets made of esparto grass, or 

 in bags bound with horsehair 

 bands. A press is filled with a 

 number of these baskets or sacks 

 separated by wooden or metal 

 perforated plates, that equalise the pressure, while allowing the oil to pass through. The 

 presses are of various kinds, some being hand-lever or screw presses, while the larger ones 

 are hydraulic. In any case the first pressure is a light one, as thereby a pure, clean oil is 

 obtained, known as " Virgin Oil." The product of a second expression is also suitable for 

 edible purposes. The marc is then broken up and mixed with hot water before the next 

 expression, and subsequently a residue of oil is sometimes extracted with such solvents as 

 carbon bisulphide or sulphuric. ether. 



The expressed oil is sprayed to get rid of the mechanical impurities and to precipitate any 

 matter in suspension, after which it is run into cisterns to allow of further separation and 



By permission of Messrs. Greenwood & Bailey, Ltd,. 



ANGLO-AMERICAN HYDRAULIC OIL PRESS 



