Document Eqo1NOLgBYzLDQ102QaXmXXb

890 CHAPTER 45 1949 Guide Table 2. Regain op Hygboscopic Materials Moisture Content Expressed in Per Cent of Dry Weight of the Substance at Various Relative Humidities--Temperature, 76 F Classi fication Material Description Relative Huwditt--Per Cent 10 20 30 40 50 60 70 80 90 Autboritt Cotton Cotton Sea island--roving American--cloth 2.5 3.7 4.6 5.5 6.6 7.9 9.5 11.5 14.1 Hartshorne 2.6 3.7 4.4 5.2 5.9 6.8 8.1 10.0 14.3 Schloesing Cotton Absorbent 4.8 9.0 12.5 15.7 18.5 20.8 22.8 24.3 25.8 Fuwa Nataral Textile Fibers Wool Silk Lipeb Australian merino--skein 4.7 7.0 8.9 10.8 12.8 14.9 17.2 19.9 23.4 Hartshorne Raw chevenoee--skein 3.2 5.5 6.9 8.0 8.9 102 11.9 14J 18.8 Schloesing Table cloth 1.9 2.9 3.6 4J 5.1 6.1 7.0 8.4 10.2 Atkinson Linen Dry spun--yarn 3.6 5.4 6.5 7.3 8.1 8.9 9.8 11.2 13.8 Sommer Jute Average of several grades 3.1 5.2 6.9 8.5 10.2 12.2 14.4 17.1 20.2 Starch Hemp Manila and sisal--nope 2.7 4.7 6.0 7.2 8.5 9.9 11.6 13.6 15.7 Fuwa Rayons Viscose Nitrocellu lose Cupnunonium Average skein Cellulose Acetate Fiber 4.0 5.7 6.8' 7.9 9.2 10.8 12.4 14.2 16.0 Robertson 0.8 1.1 1.4 1.9 2.4 3.0 3.6 4J 5.3 Robertson M. F. Newsprint. Wood pulp--24% ash 2.1 3.2 4.0 4.7 5.3 6.1 7.2 8.7 10.6 U. S. B. of S. H. M. F. Writing Wood pulp--3% ash 3.0 4.2 5.2 6.2 7.2 8.3 9.9 119 14.2 U. S.B. nfS. Paper White Bond Rag--1% ash 2.4 3.7 4.7 5.5 6.5 7.5 8.8 10.8 13.2 U.aB.ofS. Com. Ledger 75% rag--1% ash 3.2 4.2 5.0 5.6 62 6.9 8.1 10.3 13.9 U. S. B. of a Kraft Wrapping Coniferous 3.2 4.6 5.7 6.6 7.6 8.9 10.5 12.6 14.9 u.aB.ofs. Leather Sole oak--tanned 5.0 8.5 11.2 13.6 16.0 18.3 20.6 24.0 29.2 Phelps Catgut Racquet strings 4.6 72 8.6 10.2. 12.0 14.3 17.3 19.8 21.7 Fuwa Misc. Organic Clue Robber Hide Solid tires 3.4 4.8 5.8 6.6 7.6 9.0 10.7 11.8 12.5 Fuwa 0.11 0.21 0.32 0.44 0.54 0.66 0.76 0.88 0.99 Fuwa Wood Timber (sverage) 3.0 4.4 5.9 7.6 92 11.3 140 17.5 22.0 Fewest P. Labu Soap White 1.9 3.8 5.7 7.6 10.0 12.9 16.1 19.8 23.8 Fuwa Tobacco Cigarette 5.4 8-6 n'o 13.3 16.0 19.5 25.0 33.5 50 0 Ford White Bread 0.5 1.7 3.1 4.5 6.2 8.5 IM 14.5 19.0 Atkinson Crackers 2.1 2.8 3.3 3.9 5.0 6.5 8.3 10.9 14.9 Atkinson Food stuffs Macaroni Flour 5.1 7.4 8.8 10.2 117 13.7 16.2 19.0 22.1 Atkinson 2.6 4.1 5.3 6-5 8.0 9.9 12.4 15.4 19.1 Bailey Starch 2.2 3.8 5.2 6.4 7.4 8.3 9.2 10.6 12.7 Atkinson Gelatin 0.7 1.6 2.8' 3.8 4.9 6.1 7.6 9.3 11.4 Atkinson Asbestos Fiber Finely divided 0.16 0.24 0.26 0.32 0.41 0.51 0.62 0.73 0.84 Fuwa Silica Gel Misc. ' Inorganic Domestic Coke 5.7 9.8 12.7 15.2 17.2 18.8 20.2 21.5 22.6 Fuwa 0.20 0.40 0.61 0.81 1.03 1.24 1.46 1.67 1.89 Selvig Activated Charcoal Steam activated 7.1 14.3 22.8 26.2 28.3 29.2 30.0 31.1 32.7 Fuwa Sulfuric Arid 33.0 41.0 47.5 52.5 57.0 61.5 67.0 73.5 82.5 Mason When hygroscopic materials absorb moisture from the surrounding air they deliver to the air sensible heat equivalent to the latent heat released by the moisture to the material. This may account for a small part of the total heat load of the conditioned space. Conditioning and Drying In general, the exposure of materials to desirable humidities for treat ment may be coincidental with the manufacture or recessing of the Industrial Air Conditioning 891 materials, or they may be treated separately in special enclosures. This latter treatment may be classified as conditioning or drying. The purpose of conditioning or drying is usually to establish a desired condition of moisture content and to regulate the physical properties of the material. When the final moisture content is lower than the initial one, the term drying is applied (See Chapter 47). If the final moisture content is to be higher, the process is termed conditioning. In the case of some textile products and tobacco, for example, drying and conditioning may be com bined in one process for the dual purpose of removing undesirable moisture and accurately regulating the final moisture content. Frequently con ditioning or drying is made a continuous process in which the material is conveyed through an elongated compartment by suitable means and sub jected to controlled atmospheric conditions. Control of Rate of Chemical Reactions A typical example of control of the rate of chemical reactions occurs in the manufacture of rayon. The pulp sheets are conditioned, cut to size, and passed through a mercerizing process. It is essential that during this process close control of both temperature and relative humidity should be maintained. The temperature controls the rate of reaction directly, while the relative humidity maintains a constant rate of evaporation from the surface of the solution and obtains a solution of known strength throughout the mercerizing period. Another well-known example in this class is the drying of varnish which is an oxidizing process dependent upon temperature. High relative hu midities have a retarding effect on the rate of oxidization at the surface and allow the internal gases to escape freely as the chemical oxidizers cure the varnish from within. This produces a surface free from bubbles and a film homogeneous throughout. Desirable temperatures for drying varnish vary with the quality. A relative humidity of 65 per cent is beneficial for obtaining the best processing results. ' Control of Rate of Biochemical Reactions In the field of biochemical control, industrial air conditioning has been applied to many different and well-known products. All problems involv ing fermentation are classed under this heading. As biochemistry is a sub division of chemistry, subject to the same laws, the rate of reaction may be controlled by temperature. An example of this is the dough room of., the modem bakery. Yeast develops best at a temperature of 80 F. A relative humidity of 65 per cent is maintained to hold the surface of the dough open to allow the carbon dioxide gases formed by the fermentation to pass through and produce a loaf of bread, when baked, of even, fine texture without large voids. . The curing of fruits, such as bananas and lemons, also comes under this. classification. Bananas require a cycle of temperatures and relative hu midities for ripening. The starches in the pulp of the fruit must be changed and the skin cured and colored, after which the fruit is cooled to maintain as low a rate of metabolism as possible. Ideal storage conditions range between 56 and 60 F with about 75 per cent relative humidity and ventilation at the rate of three or four air changes per hour. The curing of lemons is an entirely different problem. Bananas are cured for a quick market, while lemons are held for a future market. The' process, therefore, varies in the temperature used. Temperatures from 54 to 59 F have been found to bo best suited for this process. A high rela- /