Subsequent Sorption Research Articles

Adsorption of nitrogen on silica gel, modified by the presorption of dibutyl phthalate

1. A study was made of the adsorption of nitrogen vapor at the boiling point of nitrogen on samples of silica gel that contained progressively increasing amounts of dibutyl phthalate (DBP). 2. The DBP is sorbed on the entire silica gel surface, shielding the silica gel field for the subsequent sorption of nitrogen. Nitrogen is also sorbed on the DBP surface, but with a smaller adsorption potential. 3. The area occupied by 1 DBP moleculein a dense monomolecular layer is 80 A2.

Transport of liquids in structurally modified polyethylene

AbstractCast linear polyethylene films subjected to dry and solvent annealing display markedly different sorption and difusion barrier properties than do untreated films. The subsequent sorption of liquid o‐ and p‐xylene and cis‐ and trans‐acetylene dichloride per unit volume of amorphous polymer increases as the annealing temperature and/or treating solvent concentration increases. Integral diffusivities calculated from sorption and steady‐state permeation rates show a monotonic increase with sorption per unit volume of amorphous polymer. The concentration dependence, however, is less marked than observed in similar systems at low permeant activity. Apparently the above treatment reduces the effective crosslinking imposed by the crystallites on the amorphous polymer chains through disentangling and incorporating some of these chains into crystallites. Thus the polymer is capable of a greater degree of swelling when brought into contact with a compatible liquid in a spite of a higher degree of crystallinity. The low concentration dependence of the diffusivities is probably due to heterogeneous distribution of excess permeant in a treated film. If the excess permeant were preferentially sorbed in regions of low polymer concentration then the above observations could be explained. Long‐duration, osmotic stress‐induced swelling and recrystallization have been cited to account for time‐dependent permeation rates in treated and untreated films.

Effect of Additional Cross-links on Sorption by Keratin

THE removal of cross-links between the peptide chains of keratin can lead to a considerable increase in the amount of water vapour and formic acid vapour absorbed at high relative pressures1, and similar increases in the uptake of water vapour by keratin occur after peptide bond cleavage2. This communication indicates how the introduction of additional cross-links may affect the subsequent sorption behaviour of keratin.

Adsorption of Tagged Phosphute Ions on Glass Surfaces as Related to Alkaline Attack

A preliminary investigation has been made of various factors involved in the sorption of phosphate ions on glass surfaces, particularly with reference to a possible utilization of phosphate sorption as an indicator of alkaline attack of the surface. Sorption has been measured by means of a tracer technique using radioactive phosphorus as trisodium phosphate, and tests have been made with two types of soft glass and with Pyrex‐brand glass, with and without alkaline pretreatments. Radioautographs have been prepared to determine the distribution of sorbed phosphate on soft‐glass specimens treated in various ways. The sorption of phosphate ions from dilute alkaline solutions at room temperature on fused soft glass and Pyrex‐brand glass has been found to be very slight, on the order of one‐thousandth of a μ gm. per sq. in. (roughly equivalent to a thousandth of a monomolecular layer on the macrosurface). Treatment of soft glass for a few minutes in sodium hydroxide solution at 80°C. results in a multifold increase in subsequent sorption of phosphate ions at room temperature. A much longer alkaline pretreatment is required in the case of Pyrex‐brand glass, but a similar increase in sorption is found. The different results obtained with soda‐lime and borosilicate glasses may be explained on the basis of different types of nonadsorbing surface films. Zinc ions in the alkaline pretreatment solution appear to cause an increase in subsequent sorption, and it is proposed that adsorption of polyvalent cations facilitates the adsorption of phosphate ions.