. The Bell System technical journal . 6),there will be 1240 = 150 unit cells across the fibril, and 1300 165 unit cells down through the fibril. Therefore the total numberof oxygen atoms per unit cell length in the four fibril surfaces is: 6 X 150 X 2 + 6 X 165 X 2 = 3780. From this the moisture content equivalent to a monomolecular layer is: 2 X /o°x 165 X ^ X °° = °-^^%-t * The considerations upon which these and subsequent calculations are based aregiven in detail in separate publications which will appear in the April and May issuesof Textile Research. t The Angstrom unit AU is 10
. The Bell System technical journal . 6),there will be 1240 = 150 unit cells across the fibril, and 1300 165 unit cells down through the fibril. Therefore the total numberof oxygen atoms per unit cell length in the four fibril surfaces is: 6 X 150 X 2 + 6 X 165 X 2 = 3780. From this the moisture content equivalent to a monomolecular layer is: 2 X /o°x 165 X ^ X °° = °-^^%-t * The considerations upon which these and subsequent calculations are based aregiven in detail in separate publications which will appear in the April and May issuesof Textile Research. t The Angstrom unit AU is 10~* cm. From Fig. 6 it appears that only theequivalent of one cellobiose unit may be available for surface adsorption per unitcell in the fibril surface. Furthermore, since molecules in solid or liquid surfacesare subject to unbalanced forces (surface tension) it is assumed that all surfacecellobiose units are so oriented that all 6 hydroxyl groups have surface forces capableof adsorbing water molecules. MOISTURE IN TEXTILES 237. ANGSTROM UNITSFig. 6—The cellulose unit cell or crystallite structure. 4. Hair Swelling due to Fibril Surface MoistureThe diameter of the water molecule is reported as AU. Thesurfaces of adjacent fibrils along growth ring boundaries must beseparated at least 2 X = AU when a monomolecular layer ofwater is present on each contiguous surface. This corresponds to atotal increase in hair diameter of 33 X 2 X = 500 AU. Thepercentage diameter increase in the hair is: (500/125000) X 100 = 238 BELL SYSTEM TECHNICAL JOURNAL where 125000 AU is taken as the mean diameter of the dry cottonhair. According to Conins, the coefficient of hair diameter increase withhumidity is about per cent per 1 per^cent R. H. Therefore, an in-crease of per cent in hair diameter is found at 11 = per centR. H. From adsorption data (Fig. 7) by Urquhart and WilHams/^this relative humidity corresponds to between per cent and cent mo
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