373 



Selective Permeability : The Absorption of Phenol and other 

 Solutions by the Seeds a/* Hordeum vulgare. 

 By Adrian J. Brown, F.Pi.S., and Frank Tinker, M.Sc. 

 (Eeceived July 24, 1916.) 



Previous researches on the absorption of various aqueous solutions by the 

 seeds of Hordeum (barley) have been directed mainly to a study of the 

 phenomena attending the diffusion of the. solvent through the semipermeable 

 covering of the seeds.* The latter, however, is permeable not only to the 

 water but also to certain classes of solutes in solution, such as the phenols 

 and fatty acids ; in fact, the membrane behaves in • their presence as a 

 selectively permeable one rather than a semipermeable one. In the present 

 communication we deal more particularly with the extent to which certain 

 of these permeable solutes enter the seeds together with the water, in the 

 hope that the results may throw some light on the physical causes 

 governing the phenomenon of selective permeability. 



A preliminary investigation having given the somewhat striking result that 

 phenol and aniline solutions enter the seeds in higher concentration than the 

 solutions in which they are immersed, we decided to make a series of 

 quantitative experiments with solutions of aniline, phenol and acetic acid of 

 various concentrations. 



1. Extent to which Aniline, Phenol and Acetic Acid enter the Seeds from 

 Solutions of Various Strengths. 



(a) Aniline Solutions. — The seeds were steeped in approximately N/4, 

 N/8, N/12, and N/16 solutions respectively for two days. 



The amount of aniline which had entered was found by hydrolysing the 

 seeds with dilute sulphuric acid. This operation, which was performed under 

 reflux at about 80° C, was complete in from two to three days' time. After 

 filtering, the solution was made up to a known volume, and the aniline 

 precipitated and weighed as tribromaniline.f The accuracy of the method 

 was tested by determinations of aniline solutions of known strengths, both 

 alone and in presence of barley seeds which had been hydrolysed to sugar. 

 The presence of the latter was found to have no influence on the results, 

 which were found to be accurate to 3 or 4 per cent. 



The results are given in Table I. 



* A. J. Brown, 'Koy. Soc. Proc.,' B, vol. 81, p. 82 (1909) ; ibid., with F. P. Worley, B, 

 vol. 85, p. 546 (1912) ; ibid., with F. Tinker, B, vol. 89, p. 119 (1915). 

 t Cf. section on Aniline in Allen's ' Commercial Organic Analysis.' 



