26 BULLETIN 867, U. S. DEPARTMENT OF AGRICULTURE. 



vided with indicators to record the level of the contents, or when 

 buried under ground with indicators above ground to register the 

 contents. 



Heretofore there has not been much inducement for manufacturers 

 to prepare a high-grade No. 3 oil. Consequently, the generally 

 recognized darkening effect of heat due to steaming off has not been 

 considered. If, however, effort is made to produce a high-grade oil 

 with a minimum of color, care must be exercised not to expose 

 the oil in the solvent-recovery still or oil-finishing still to this high 

 temperature. 



By such solvent extraction, as generally practiced, a pomace is 

 produced running from 10 to 12 per cent of moisture and containing 

 anywhere from 0.6 to 2 per cent of oil. This low content of oil can 

 be attained only by very efficient extraction, determined by the kind 

 of solvent used, the number and efficiency of the washings, and the 

 type of equipment. 



SOLVENT-EXTRACTED NO. 1 OIL. 



In the course of the work of tins laboratory on the technology of 

 castor-oil manufacture, evidence has been obtained which indicates 

 that a very promising oil of apparently No. 1 grade can be made 

 entirely hj the solvent process. Without decorticating the beans, 

 they were slightly crushed in order to break the seed coats and ex- 

 tracted with benzol by percolation. The solvent saturated with 

 oil was of a characteristic light-green color, similar to oil always 

 produced by such extraction. The benzol was evaporated at atmos- 

 pheric pressure until toward the end of the distillation, whereupon 

 a vacuum was applied. The residual oil with greenish 3 T ellow color 

 was then heated to 95° to 110° C. at atmospheric pressure and treated 

 with 5 per cent of fuller's earth with constant agitation for about 

 10 minutes, whereupon 2 per cent of decolorizing carbon was added 

 and the stirring continued, while the temperature was allowed to 

 fall slowly to about 90° C. At the expiration of about 15 minutes 

 the oil was filtered and came through with a light straw color. Inas- i 

 much as every castor-oil expelling plant must have an auxiliary 

 extraction equipment, it follows that if a satisfactory grade of oil, 

 colorless and low in acidity, can be made by such means it will mate- 

 rially reduce the cost of production. 



TREATMENT OF POMACE. 



The dry, more or less dusty pomace from the extraction house is 

 conveyed to the pomace warehouse. If it is lumpy, it is passed 

 through a grinding machine, which may be of the rotating-disk type, 

 spiked-roller (crusher), or swinging-hammer type, where it is pulver- 

 ized. If the moisture runs above 12 per cent, decomposition may 

 set in, resulting in an appreciable loss of ammonia, the only con- 

 stituent of real commercial value. 



