Various anomalies in the thermodynamic and kinetic properties of ion-exchange resins are attributed to a non-uniform distribution of the gegen-ions. It is suggested that some information on this distribution should be derivable from the correlation of a number of electro-kinetic properties of the resin. Electrical conductance and electro-osmosis have been studied using a highly swollen cation-exchanger and the results combined with previous determinations of ionic self-diffusion coefficients and transport numbers.At one temperature and concentration a fairly detailed application of the irreversible thermodynamic theory of membrane phenomena has been possible and this is tentatively extended to other concentrations. It appears that for resins containing little or no sorbed electrolyte the interaction between the gegen-ions and the matrix is important and also has the effect of concentrating the gegen-ions into regions of relatively high solution viscosity. In the presence of sorbed electrolyte these effects, per mole of cations, become less significant.The electro-osmotic permeability of the resin decreases by about 25 % as the external solution concentration is increased from 0.01 to 1-00 M. This suggests that the interaction between gegen-ions and matrix does not take the form of specific ion-pairing, association or incomplete dissociation, but that it is due to electrostatic interactions controlling the distributions of the ions in the pore solution. An analysis is given in terms of a general distribution of the gegen-ions which shows that these conclusions are consistent with the experimental data and electrostatic theory.The implications of these results with regard to the convection contribution to electrical conduction are considered in the light of the conductance and diffusion coefficient data. The difficulties in computing the convection current from the electro-osmotic permeability are pointed out and an attempt made to estimate the diffusion coefficient of H+ ions from the conductance of the H+-form resin.
It is well known that cabbage contains thermolabile sulfur compounds which evolve sulfurous odors. Simpson and Halliday (22) investigated the volatile sulfur produced by boiling cabbage during the period of cooking. The formation of hydrogen sulfide was attributed to the hydrolysis of allyl isothiocyanate, the mustard oil of the thioglucoside sinigrin. Masters and Garbutt (16) similarly described the volatile sulfur as sulfide sulfur, but made no identification of the volatile organic sulfur.The present investigation identifies the volatile divalent sulfur compounds of cooked cabbage. For this purpose a train of absorption traps is utilized modifying the procedure of Challenger and Rawlings (7).It is also shown that the major volatile sulfur component of cooked cabbage is derived from L-S-methylcysteine sulfoxide, a free amino acid occurring in cabbage, first described by Synge and Wood (24), and reported to account for a substantial proportion of the organic sulfur of cabbage.The relationship between therniolabile precursors and volatile sulfur is of considerable importance to flavor, if one accepts the supposition that odors commonly described as disagreeable may contribute to an acceptable flavor, and be considered normal constituents of the aroma, when present in trace amounts. Examples of such a possible role for sulfur compounds are: hydrogen sulfide and mercaptans in beer (51, the brothlike flavor of 3-methylmercaptopropionaldehyde (17), ethyl 3-niethylthiopropionate in pineapple (12), allyl isothiocyanate in mustard ( l l ) , etc.
EXPERIMENTALVolatile sulfur, train analysis. The train of traps illustrated in Figure 1 was used for qualitative identification of volatile sulfur compounds. A head of cabbage (600 g.) was dispersed in a Waring blender with 150 ml. of distilled water. A 250 g. aliquot of the slurry was placed in a 500 ml. round-bottom flask, to which was fitted an adapter with gas inlet and a 20 cm. Allihn condenser. The train of traps consisted of (a) anhydrous calcium chloride, (b) lead acetate (s.) (Pb(C?HsO,)? * 3H20), (c) 4% mercuric cyanide (aq.), and (d) 3% mercuric chloride (aq.). The calcium chloride and lead acetate traps separated hydrogen sulfide from organic sulfur (20). The slurry was aerated with commercially purified nitrogen at the rate of 100 ml./min. by applying a vacuum a t the end of the train. After 6 hours no precipitate was observed in the mercury salt solutions. The slurry was then boiled under reflux and aeration continued overnight.Lead sulfide was formed in the lead acetate trap in a few minutes. I n 20 to 50 minutes '
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