6 BULLETIN 632, U. S. DEPARTMENT OP AGRICULTURE. 



method is in the better quality of the product obtained. Pressed oils 

 usually contain less impurities and consequently are more readily 

 and effectively refined. 



When the maximum percentage of oil is desired from certain ma- 

 terials the volatile-solvent method of extraction serves best. The 

 principal solvents which may be employed are benzine, petroleum 

 ether, gasoline, and carbon tetrachlorid. A disadvantage of this 

 method is in the inflammability of many of the solvents, necessi- 

 tating careful handling and operation. This trouble is largely over- 

 come by the use of carbon tetrachlorid, which is noninflammable and 

 possesses a higher boiling point than any of the other solvents and 

 hence is capable of effecting more complete recovery. Oils obtained 

 by the solvent extraction method are usually less pure than expressed 

 oils, containing much coloring matter and other impurities extracted 

 by the particular solvent employed. Xo great difficulty is experi- 

 enced, however, in refining the oils thus obtained. Pressed oils also 

 require refining. 



Apparatus of the continuous-extraction type is usually employed. 

 This kind of apparatus minimizes the quantity of solvent used and 

 prevents loss of the solvent during the operation. Practically all the 

 solvent may be recovered from the oil and residue and thus be avail- 

 able for further use. A practical example of the use of a volatile 

 solvent for the extraction of fatty oil is the use of benzine in the ex- 

 traction of soy-bean oil (11). The disadvantages of the solvent 

 method as compared with the advantages of the pressure method 

 are largely offset by the lower cost of the apparatus, the smaller ex- 

 pense of operation, and the higher yield of oil obtainable. 



Continuous extractors and hydraulic presses are obtainable from 

 American manufacturers of chemical and pharmaceutical machinery. 



Either of the two methods mentioned may be used effectively in 

 the extraction of oil from tomato seeds. The solvent extraction 

 method was used for obtaining the samples in the experiments de- 

 scribed in this bulletin. The apparatus employed was the contin- 

 uous-extraction type, the solvents used being ether and carbon tetra- 

 chlorid. The yield of oil from the ground seeds with either solvent 

 was practically the same, averaging 22 per cent. The crude oil was 

 pale greenish yellow in color with a fatty, slightly rancid odor and 

 fatty, slightly bitter taste. 



In refining the crude oil the objectionable odor was removed by 

 passing steam through the oil until little or no odor was perceptible. 

 The deodorized oil was then heated on a steam bath for about one 

 hour with fuller's earth (kaolin) and finally filtered while hot 

 through filter paper. This procedure effected decolorization of the 

 oil to a marked degree. The refined oil possessed a very pale yel- 

 lowish color with bland fatty and agreeable nutlike taste and smell. 



