516 MARINE PRODUCTS OF COMMERCE 



to the pockets in the die rolls, each ribbon forming one-half the capsule. The 

 pressure of the die rolls seals the ribbons together, completing the capsule con- 

 taining a globule of the concentrate. The globule is then punched from the ribbon 

 and the finished capsule is cooled by a stream of air and washed in a bath of 

 naphtha to remove the coating of mineral oil. The completed capsules are collected 

 in trays for bottling, or stored for future use. The capsules are prepared at a rate of 

 60,000 to 75,000 per hour at a cost of approximately 10 cents per 100. This 

 method has almost universal use in the capsulation of vitamin concentrates. 



Concentration of Vitamin A 



Saponification Method. Many patents have been issued covering processes for 

 the concentration of vitamin A in fish-liver oils. These contain descriptions of tech- 

 niques and physical and chemical methods for separating the unsaponifiable mate- 

 rial in which the concentrate is found. The agents used and concentrations and 

 temperatures are also contained in the patent literature. 



The process in general consists of splitting the triglycerides of oil into glycerol 

 and fatty acids, which are then combined into soaps. Unsaponifiable material con- 

 taining vitamin A is then separated by means of solvents. The methods used to 

 complete this separation involve alkalies, enzymes, acids, or synthetic organic 

 catalysts. 



The saponification method is most generally used by most of the processors. 

 One of the deciding factors in treating liver oils by this method is the percentage of 

 unsaponifiable material contained in the oil. An oil having a high percentage of 

 unsaponifiable material and a low vitamin A potency cannot be converted into a 

 concentrate by this method. 



According to the U.S. P. definition, a concentrate is one in which the potency 

 of vitamin A is 200,000 units or more per g. Some species of shark livers cannot 

 be concentrated above 50,000 units because of the high unsaponifiable fraction in 

 the oil. Such oils as these are usually concentrated further by one of the other 

 methods. 



Concentration by Molecular Distillation. Molecular distillation of products of 

 high molecular weight has been available as a laboratory tool for many years. It 

 was not until 1934 that real progress was made toward adapting laboratory 

 methods to commercial processes. This resulted from research on high-vacuum 

 photographic film drying and the development of high-vacuum condensation and 

 fractionating pumps. 



The presence of noncondensable gases in high molecular weight compounds 

 exerts a definite retarding influence on their distillation. The construction and 

 operation of the molecular still as it is commercially used at present compensates 

 for these inequalities. The high vacuum in the region of 1 micron (0.001 mm 

 mercury) pressure in an enclosed vessel eliminates the interference of molecules 

 of dissolved and entrapped gases. This makes it possible to distill the long molecule 

 of organic compounds without breaking them when they are exposed to moderate 

 heat for a short time. The molecules of gas and of the organic substance are re- 

 moved from the presence of the decomposing substance by means of the high- 

 vacuum pump and are condensed in fractions according to their molecular weights. 

 Included in the group of substances which can be distilled by this means are fats, 

 waxes, resins, vitamins, sterols, and many others. 



