FISH-LIVER OILS 517 



The molecular distilling apparatus is composed of a rotating disc heated by an 

 electric resistance unit, with a beehive-shaped condenser over the face of the 

 disc. This is enclosed in a tight vessel to which vacuum pumps are attached. The 

 disc has a trough at the outer edge in which a syphon dips to remove the un- 

 distilled oil. The oil to be distilled drops onto the center of the rotating disc and 

 rapidly traverses the surface and is retained by the trough. The portion of the 

 substance having low molecular weight evaporates, is condensed on the condenser 

 coils, and is collected in a receptacle. The higher molecular weight portion is 

 caught in the trough at the edge and is syphoned off; it goes through the 

 same process in another still operated at a slightly higher temperature. 



The stills in use at present for distilling vitamin A from fish-liver oils contain 

 a rotating disc, 32 inches in diameter and heated to a temperature of 266° F 

 (130° C). These discs rotate at 3,000 to 5,000 rpm and are operated in a series 

 containing 21 stills. These stills handle 500 to 1,000 pounds of fish-liver oil per 

 hour. 



There are five fractions in the distillation of fish-liver oils: (1) removal of gases; 

 (2) products of rancidity and protein, which are rejected; (3) sterols, free fatty 

 acids, esters, glyceride esters, natural preservatives, tocopherols (vitamin E), 

 and their esters, which are given further distillation; (4) vitamin A and its esters, 

 retained in storage and blending tanks; (5) glyceride fat residue, either sold for 

 food or industrial purposes separately or combined with the residue from final 

 vitamin E fraction, depending upon market conditions for nontocopherols. 



The vitamin D fraction cannot be recovered economically to compete with 

 manufacture of the synthetic product. Vitamin A is recovered as a concentrate 

 ready for use as a dietary ingredient, and vitamin E is recovered for use after 

 its final distillation. 



"Solexol" Process for Concentrating Vitamin A. Passino (1949) has described 

 a patented process for fractionating fish and fish-liver oils. This process is based 

 upon the solubility of the oils in a hydrocarbon solvent, generally propane. The 

 separation of the oil into fractions is controlled by regulating the temperature and 

 pressure. The process has not been placed in any plant preparing vitamin A con- 

 centrates in the United States. All results reported at the present time have been 

 obtained in the original plant set up for experimental purposes by the designers. 



The apparatus is composed of several towers, the number depending upon the 

 complexity of the oil or fat being fractionated. In the case of menhaden and 

 sardine oils three towers are required, while cod-liver oil requires only two. In 

 handling fish and fish-liver oils the first operation consists of neutralizing the oil 

 with caustic and mixing it with liquid propane. The soap formed and the coloring 

 matter are eliminated in the first tower. This portion averages approximately 2 per 

 cent. The remaining portion passes into the second tower, where about 20 per cent 

 is eliminated at the bottom of the tower by adjusting the temperature and pressure. 

 The remainder of the solution then passes into the third tower, where conditions 

 are again adjusted and all except approximately 10 per cent containing the vitamin 

 A is eliminated. The final vitamin A concentrate is drawn off as an overhead 

 product. 



Fractionation of sardine and cod-liver oils proceeds through the process in 

 similar steps. The percentages recovered from the different steps varies as does 



