Multistage column experiments have been performed using a mixed bed of finely divided weakly acidic and weakly basic ion-exchange resins with thermal regeneration of the resins at 80�. A product water fraction with a concentration of 200- 250 p.p.m. can be obtained using such a column from a feed water containing 1000 p.p.m. of sodium chloride. When the same feed water is used as the regenerant at 803 an effluent having a peak concentration of about 5000 p.p.m. can be obtained. A solution of 1000 p.p.m. magnesium sulphate can be similarly demineralized. The performance of the resin column is highly dependent on the pH value to which it has been buffered by prior treatment with acid or alkali. It is also shown that thermal regeneration is feasible when the resins are used in a softening cycle.

Weakly basic ion-exchange resins have been synthesized by treating crosslinked chloromethylated polystyrene beads with primary and secondary amines and with polyamines. Titration curve data show that such resins may be either homofunctional and possess flat titration curves, or heterofunctional and possess sloping titration curves, depending on whether the basic sites within the resin have the same or different basicities. A comparison of the titration curves determined at c. 20' or 80" reveals that all amine resins become weaker bases when heated, but the maximum effect is shown by the resins with homofunctional structures; e.g. the plateau-shaped curves at c. 20' and 80" of a polyvinylbenzyldiethylamine resin differ by about 1.2 of a p H unit at half neutralization. The ~ffect is fully reversible.The influence of amino group substituents, crosslinking, salt concentration, sulphate ions, and temperature on the titration curves of weakly basic amine resins has been studied. Titration curves of a variety of commercial amine resins have been determined a t c. 20' and 80" and show t h a t a t least two resins with homofunctional structures are commercially available.In the first paper in this series1 it was shown, from an analysis of the factors influencing the salinity of water supplies, that the production of municipal and industrial waters in the future will need a cheap method of demineralization for use in conjunction with conventional methods of water supply, if locally available waters are to be used and reused extensively. There is therefore a major need developing for a method of removing at low cost small amounts (500 p.p.m.) of salinity from waters of marginal quality. An analysis of the principles of demineralizatiod reveals that the process with the greatest potential for this purpose would use adsorbents, such as ion-exchange resins, which can be regenerated with heat rather than chemicals. Such an ion-exchange process, which will be designated the "Sirotherm" process,$ is being developed in these laboratoriea and is the subject of this and the following papers.The Sirotherm process uses weakly basic ion-exchange resins in admixture with weakly acidic resins for the adsorption of salts from an aqueous solution in a thermally variable manner. Weakly basic resins may be made with different basicities,

SYNOPSISWood fiber-synthetic polymer composites arc being studied with n view to using, in building or packaging, residues from the production of sawlogs and wood resources which are unsuitable for timber, pulp, or paper production. The structure of wood fibers and the properties required in a fiber intended for use as a reinforcing agent are described briefly.Laminates comprising 67% by weight of cellulose fibers have been produced by hot-pressing sheets of paper coated with low-density polyethylene. Mechanical properties of the laminates have been studied with particular attention to the effects of exposure to moisture. The flexural properties of the laminates at low relative humidities compared favorably with those of glaspfilled high-density polyethylene and of paper-phenolic resin laminates but declined more at high relative humidities. 143

SynopsisFlexural properties of laminates prepared by hot pressing commercial papers and laboratory handsheets with films of polyolefins were measured following exposure to different levels of moisture. Prior to their incorporation in the laminates, the fibers, either individually or as preformed paper, were acetylated or crosslinked with formaldehyde to reduce their sensitivity to moisture. The results are compared with earlier measurements which showed that the properties of laminates based on paper precoated with polyethylene declined sharply a t high relative humidities. For laminates comprising laboratory handsheets made from acetylated fibers, the decline in properties is less but the initial values under dry conditions are lower also. However, acetylation or crosslinking of preformed paper improves up to threefold the retention of flexural modulus by the laminates under the wettest conditions with no concurrent loss in this property under dry conditions, although some embrittlement of the component paper sheets is observed. Enhanced fiber alignment or the addition of 5% glass fibers to the paper does not arrest the decline in flexural properties of the laminates with increasing relative humidity. This decline differs little when other polyolefins are used but is accentuated when ethylene-vinyl acetate copolymer is the binder.

Electronically conducting polymers have been prepared by treating hexachlorobenzene with sodium at 3003, using sodium chloride as a diluent. The products, presumably polybenzenes, have resistivities of 0.2-25 ohm om depending on the amount of sodium used; less crosslinked polymers similarly prepared from 1,2,4-trichlorobenzene have resistiveties some thousand times greater. I t has been confirmed that the reaction of sulphur with anthracene at 400' yields conducting polymers whose resistivity decreases with increasing sulphur content. A product containing 54% sulphur had a resistivity of 330 ohm cm.The data presented show that good conductors can be obtained without the presence of hetero atoms within the aromatic network of the macromolecules.The previous papers in this series have described crosslinked, non-planar polymers containing hetero nitrogen atoms in high concentrations. These polymers, with the exception of the polyimidazoles, are comparatively good conductors of electricity?-4 The importance of the hetero atoms in achieving the levels of conductivity observed is not known, but would be expected to be small since substituents such as iodine atoms, or the presence of strong charge-transfer complexes, do not enormously influence the electrical conductivity of p~l y p y r r o l e .~~~ However, Gibson et al.5 prepared insoluble polymers, presumably polybenzenes, by the reaction of hexachlorobenzene with sodium and since these were reported not t o conduct electricity it might be inferred that the good conductivity of the closely related polypyrroles is due to the presence of hetero atoms. Gibson's results are all the more surprising since Akamatu and Inokuchis prepared a series of polymers of fair conductivity by treating aromatic hydrocarbons with sulphur. Direct crosslinking of the aromatic rings, which would be expected to occur in Gibson's polymers, ought t o permit greater orbital overlap, and therefore better conductivity, than would result when the rings are pushed further apart by bridging sulphur atoms.