658 VI. CAROTENOIDS AND RELATED COMPOUNDS 



are the finely pulverized samples. The average range of particle size of 

 certain adsorbents varies from 1.2 )n for light calcium carbonate and 1.5 ^ 

 for floridin, floridin XXF, and magnesium oxide, to 10 m for acid clay 

 (Java) and 10.5 n for hydrated gypsum, while commercial alumina (pro- 

 duced in the laboratoiy) has an average granule size of 2 ii, and calcium 

 hydroxide, also produced in the laboratory, averages 2.5 /x. The particles 

 of the alumina standardized according to the Brockmann method^^'^ have a 

 mean size of 7 ju.^^'' The type of adsorbent which is most useful depends 

 upon whether it is used with an anhydrous solvent or with an aqueous 

 medium. In the former case any moisture is generally harmful; in the 

 latter instance, the adsorbent must not fix water or swell, for this will tend 

 to form gaps in the column. 



There are a number of different adsorbents which have been more or less 

 frequently employed. These include powdered sucrose,^"^"^^^-^^^ lactose 

 (Winterstein and Stein), ^-^ inulin (Spoehr),^-^ as well as various types of 

 alumina such as "fibrous alumina" (Wislicenus),^^^ Merck's alumina, alumi- 

 num oxide-hydrate, and "Hydralo" as recommended by Strain. ^'"'^2* 

 Magnesium oxide may be especially satisfactory, according to Euler and 

 Gard,^'^ and Strain,^^'^^^'^" while calcium hydroxide (Karrer and Walker), "^ 

 calcium sulfate (Karrer and Weber), ^^^ and calcium carbonate 

 (Tswett),*"^"^^^ are frequently employed. Bleaching earths, which are 

 hydrated aluminum silicates having widely varying calcium, magnesium, 

 and iron contents, include Frankonite KL (Koschara)^^^ and floridins XXF 

 and XS.^^^'^^^ Fuller's earth is sometimes used; it is designated as Lloyd 

 reagent. Cerecedo and Hennessy^^^ have emploj^ed the Zeolite known as 

 "Decalso." Less frequently used adsorbents are anhydrous sodium sul- 

 fate, lead sulfide, talc, kieselguhr, infusorial earths, kaolin, silica gel 

 ("intermediate activated," Silica Gel Corporation, Baltimore, Md.) and 

 also the Moosburg clays known as "Tonsil" and "Clarit." A number of 

 charcoals are sometimes satisfactory, such as "Carboraffin" (produced by 

 carbonization of pine wood with zinc chloride), "Norite," and various blood 

 charcoals. "Amberlite" and similar resins are especially effective, but 

 their deep color renders their use quite limited. 



A number of types of apparatus are employed. For a further discussion 



620 H. Brockmann and H. Schodder, Ber., 74, 73-78 (1941). 



621 H. H. Strain, Science, 83, 241-242 (1936). 



622 A. Winterstein and G. Stein, Z. phijsiol. Chem., 220, 247-263, 263-277 (1933). 



623 H. A. Spoehr, Plant Physiol, 13, 207-208 (1938). 



62^ H. Wislicenus, Collegium, 1906. Cited by L. Zechmeister and L. v. Cholnoky, 

 Progress in Chromatography, 1938-1947, Chapman & Hall, London, 1950, p. 46. 



625 H. H. Strain, J. Biol. Chem., 105, 523-535 (1934). 



626 H. 11. Strain, /. Am. Chem. Soc, 57, 758-761 (1935). 



627 H. H. Strain, Scie7ice, 79, 325-326 (li)34). 



628 p. Kan-er and II. M. Weber, Hclv. Chim. Ada, 19, 1025-1027 (I93()). 



629 L. R. Cerecedo and D. J. Ileunessy, J. Am. Chem. Soc, 59, 1617-1619 (1937). 



