In 1948 RAMSEY AND PATTERSON~ described a method for the separation and determination of the straight-chain saturated fatty acids C, to C,, by partition chromatography.
By this method the fatty acids are separated on a column of silicic acid, using methanol as the immobile solvent, isuoctane as the mobile solvent, and bromocresolgreen as the indicator. The separated acids are titrated with standard sodiumethylate and identified by their thresholdvolumes.
Applying a semimicro-modification of this method in a study on the composition of certain fats, this method proved to give very satisfactory results. However, according to the statement of RAMSEY AND PATTERSON, "the most critical requirement of this chromatographic method is a suitable silicic acid". I~AMSEY AND PATTERSON tested a riumber of different samples of silicic acid; MALLINCK-RODT'S A. R. precipitated powder was found to be most suitable. Silicic acid prepared in their laboratory from different lots of commercial waterglass appeared to be not entirely satisfactory.
Among the many samples of silicagel we tested, there was only one (a medicinal gel) which was suitable, but it was of unkwown origin. All other samples of gel proved to be unusable. Gels prepared by the procedure of GORDON, MARTIN AND SYNGE~, or by modifications of this procedure gave products unfit for use.
We succeeded however in finding a rather simple procedure for the preparation of a silicagel which in our experiments never failed to give excellent results.
PREPARATION
OF SILICAGEL To zoo ml of commercial waterglass (s.g. x.35) 400 ml of water, some drops of methyl red solution and, while stirring, IO N HCl are added until the mixture remains pink during at least half an hour. Then the resulting porridge is rubbed in a mortar in order to break up the lumps, after which more IO N HCl is added until acid to thymolblue paper. Next the silicic acid is filtered on a Bfichner funnel and washed with distilled water, without allowing the precipitate to References p. 331, Refcrerrccs p. 332.
I Wsahblad, 45 (1949) 480. ELSDEN, Biocirsm. J., 40 (x946) 252.