Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

80 EXPERIMENTAL METHODS FOR SLOW REACTIONSD~sty,~~. The preparation of liquid-solid and solid types of columns is describedquite clearly by Purne112”. The inert solid support for GLC is usually kicselguhr.The quantity of the stationary phase is usually 5 or 10 % by weight but can beas high as 30 %. Since the liquid is inevitably removed from the column to someextent, the lower the proportion of liquid, the shorter the column life. Liquid isdeposited on the solid by dissolving the stationary phase in a volatile solvent,mixing with the solid to form a slurry, and removing the solvent by means of arotary evaporator. The choice of a suitable liquid for a particular analysis remainsa difficult problem. Rough guides are given in the various books on chromatographyand by suppliers of commercial gas chromatographs, whereas particular informationcan be obtained from past literature on similar kinetic studies. Two veryuseful stationary phases for the analysis of liquids are p-p’-oxydipropionitrile andpolypropylene glycol.The usual solids for GSC are charcoal, silica gel, alumina and molecular sieves.Adsorption columns are very efficient for the analysis of gases. The gases that canbe separated on these solids (unpoisoned) are276Activated charcoal H,, 0, + N,, CO, NO, CH,Silica gelCH4, CzHs, CO, C2H4AluminaCzH4, C3H8, C3H6, cYclo-C,H6Lindesieve 5A or 13X H,, O,, N,, CH,, CO, C3H620 15 10 5 0 10 5Tlme (rnln)Fig. 52. The effect of a tailing reducer on alumina; (a) on untreated activated alumina, (b) onactivated alumina poisoned with 2 % of dinonyl phthalate. From ref. 276.