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SynopsisPolymetaphosphate and polyethylene glycol in aqueous aolution are excluded completely from rayon fibers. Determinations of nonsolvent water (6) with these reference substanres give the same value which can be used as a measure of the true swelling. The polymers can, however, penetrate into porous areas present in cotton. The average polymer concentration inside these areas is lower than in the external solution. High speed centrifugation results in decreased 6 values, which is explained by a compression of the porous areas. Higher 6 values are obtained as the molecular weight of the reference substanre is increased. With polymetaphosphate the 6 values decrease when the external concentration is increased, whereas with polyglycol the 6 value within a wide range is independent of the concentration.Nonsolvent water (6) in cotton has been determined by several workers using common electrolytes such as sodium chloride, sodium t h i~s u l f a t e ,~-~ and potassium cyanocobaltate(III)6 as reference substances. A comparison between the published results of various authors shows that the 6 values are largely dependent upon the type of electrolyte. Similarly, the concentration has an appreciable effect, which, however, has been disregarded by most authors.I n earlier papers polyelectrolytes (chiefly polynietaphosphate) were used as reference substances in determinations of nonsolvent water in rayon,' cellulose films,8 and wood pulps.9 It was shown that in favorable cases the 6 values can be used as a measure of the total amount of water inside the cellulose phase. The present paper deals with the nonsolvent water in cotton fibers with polymetaphosphate and polyethylene glycol5 as reference substances. A comparison with the results obtained with other cellulose materials is also given. I n order to elucidate the mechanism some experiments with low molecular weight electrolytes are also reported.

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