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HEATING VENTILATINC AIR CONDITIONING CUIDE 1944 Table 2. Regain of Hygroscopic Materials Moisture Content Expressed in Per Cent of Dry Weight of the Substance at Various Relative Humidities--Temperature, 75 F ClA8I* PICAT10I Material Description Relative Humidity--Per Cent 10 20 30 40 50 60 70 80 90 Authority Natural Textile fibers Rayons Cotton Sea island--roving 15 3.7 4.6 S3 6.6 7.9 9.5 11.5 14.1 Hartshorne Cotton American--cloth 2.6 3.7 4.4 5a 5.9 6.8 8.1 10.0 143 ScbJoesing Cotton Absorbent 4A 9.0 115 15.7 18.5 208 218 24.3 25.8 Fuwa Wool Australian merino--skein 4.7 7.0 8.9 10.8 118 14.9 17.2 19.9 23.4 Hartshorne Silk Raw cbevennes--akein 3.2 5.5 6.9 8.0 8.9 10.2 11.9 14.3 18.8 Sehloesing Llrwn linen Table cloth Dry spun--yarn 1.9 19 3.6 4.3 5.1 6.1 7.0 8.4 10.2 Atkinson 3.6 5.4 6^ 7.3 8.1 8.9 9.8 11.2 13.8 Sommer Jute ' Average of several grades 3.1 5.2 6.9 8a 10.2 112 14.4 17.1 20.2 Starch Hemp Manila and sisal--rope 2.7 4.7 6.0 7.2 8.5 9.9 11.6 13.6 15.7 Fawa Vtscoee Nitrocellu lose Cupramonium Average stem a4.0 5.7 6.8 7.9 9 10.8 114 14.2 16.0 Robertson Cellulose Acetate Fibre M. F. Newsprint H. M. F. Writing Paper White Bond Com. Ledger Kraft Wrapping Leather Catgut Misc. Glue Organio Rubber Materials Wood Soap- Tobacco White Bread Wood palp--24% ash Wood pulp--3% ash Rag--1% ash % rag--1% ash Coniferous Sole oak--tanned Racquet strings Hide 5oDd tire Timber (average) White Cigarette Crackers Food- Macaroni Flour Starch . (jeiatio tLsbestoa Fiber ! Inely divided Misc. alia Gel - Inorganic Idomestic Calm . iMaterials ctivated Charcoal team activated 8ulphnric Add SO. 0.8 1.1 1.4 1.9 14 3.0 3.6 43 S3 Robertson a11 3a 4.0 4.7 5.3 6.1 7 8.7 106 U.RB.ofa 3.0 43 5.2 6.2 7.2 83 9.9 11.9 14.2 U.S.B. of& 2.4 3.7 4.7 5.5 6.5 73 8.8 108 13.2 u. s.b. oia 3.2 4.2 5.0 5.6 6.2 6.9 8.1 10.3 13.9 o.aB. of a 3.2 4.6 5.7 6.6 7.6 8.9 10.5 116 14.9 U. 8. B. of S. 5.0 15 1U 13.6. 16.0 18.3 20.6 24.0 29.2 Phelps 4.6 73 8.6 10.2 110 14.3 17.3 19.8 2I;7 Fuwa 3.4 4.8 S3 6.6 7.6 9.0 107 11.8 115 Fuwa 0.11 0.21 0.32 0.44 0.54 * 0.66 076 088 0.99 Fuwa 3.0 4.4 5.9 7.6 93 1U 14.0 17.5 210 Forest P. Lab. L9 3.8 5.7 7.6 too 119 16.1 19.8 23.8 ?uwa 5.4 8.6 11.0 13.3 16.0 193 25.0 333 500 ?ord 0.5 1.7 3.1 4.5 6.2 83 11.1 143 19.0 Atkinson 2.1 2.8 33 3.9 5.0, 63 8.3 109 14.9 Ltkinson 5.1 7.4 8.8 102 11.7 13.7 6.2 19.0 211 Ltkinson 2.6 4.1 5.3 6-5 8.0 9.9 14 5.4- 9.1 lailey sa a12 3.8 6.4 7.4 83 9 0.6 17 i ltkinson 0.7 1.6 IS 3 4.9 6.1 7.6 9.3 1.4 l Ltkinson 0.16 0.24 0.26 032 041 051 062 073 0.841^uwa sa a 25.7 9.8 1 17 1 i 7 i 8.8 02 3 13 3*2.6 I^uwa 0.20 0.40 0161 081 1.03 1.24 1.46 1.67 1.89 8lelvig 6a7.1 143 218 2 .283 29.2 3OO 3 LI 317 I"uwa 33.0 41.0 415 515 5 7JO 613 67.0 733 a23 Eason 710 CHAPTER 39. INDUSTRIAL AIR CONDITIONING content of materials having a vegetable or animal origin, and to a lesser extent minerals in certain forms, comes to equilibrium with the moisture of the surrounding air. . In industries where the physical properties of a product affect its value, the percentage of moisture is of special importance. With increase in moisture content, hygroscopic materials ordinarily become softer and more pliable. Standards of regain are firmly fixed in trade with fair penalties for excesses. Deficiencies result in loss of revenue to seller and loss of desirable quality to buyer. Manufacturing economy therefore requires that the moisture content be maintained at a percentage favorable to rapid and satisfactory manipu lation and to a minimum loss of material through breakage. A uniform condition is desirable in order that high speed machinery may be adjusted permanently for the desired production with a minimum loss from delays, wastage of raw material and defective product. In the processing of hygroscopic materials, it is usually necessary to secure a fined moisture content suitable for the goods as shipped. Where the goods are sold by weight, it is proper that they contain a normal or standard moisture content. J Moisture Content and Regain The terms moisture content and regain refer to the amount of moisture in hygroscopic materials. Moisture content is the more general term and refers either to free moisture (as in a sponge) or to hygroscopic moisture (which varies with atmospheric conditions). It is usually expressed as a percentage of the total weight of material. Regain is more specific and refers only to hygroscopic moisture. It is expressed as a percentage of the bone-dry weight of material. For example, if a sample of cloth weighing 100.0 grains is dried to a bone-dry weight of 93.0grains, the loss in weight, or 7.0 grains, represents the weight of moisture originally contained. This expressed as a percentage of the total weight (100.0 grains). gives the moisture content or 7 per cent. The regain, which is expressed as a percentage of the bone-dry weight, is 7 0 or 7.5 per cent. The use of the term regain does not imply that the material as a whole has been completely dried out and has re-absorbed moisture. During the processing of certain textiles, for instance, complete drying during manu facturing is avoided sis it might appreciably reduce the ability of the material to re-absorb moisture. A basis for calculating the regain of textiles is obtained by drying under standard conditions; a sample from the lot and the dry weight thus obtained is used as a basis in the calcu lations to determine the regain. The moisture content of a hygroscopic material at any time depends upon the nature of the material and upon the temperature and especially the relative humidity of the air to which it has been exposed. Not only do different materials acquire various percentages of moisture after prolonged exposure to a given atmosphere, but the rate of absorption or drying varies with the nature of the material, its thickness and density. Table 2 shows the regain or hygroscopic moisture content of several 711