May, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
showed an average gain of approximately 35% in nonvolatile content over the average for the commercial lacquers. Coldcheck resistance wm intermediate between lacquers B and C. In other respects formulas 6 to 8 were comparable to commercial lacquers. Although formulas 10 to 12, inclusive (1:2 nitrocellu1ose:resin ratio), and 14 to 16, inclusive (1:3 ratio), showed progressively higher nonvelatile content, they were, in general, inferior t o the commercial lacquers. EFFECT OF RESIN AND PLASTICIZER
The only property affected adversely to any marked extent by the use of viscosity types below RS 1/2-second nitrocellulose was temperature-change resistance. Improved performance of lacquers with respect t o this property was accomplished by proper selection of both resin and plasticizer (Table 111). The direct substitution of Glyptal2477'for Aroplaz 905 and of dioctyl phthalate for a mixture of equal parts of dibutyl phthalate and raw castor oil improved temperature-change resistance in formulas based on 1/4-secondand 30-35 centipoise types without changing the other properties of the lacquers to any extent. Excellent cold-check resistance was obtained in the composition containing RS 1/4-second nitrocellulose and good cold-check resistance in the lacquer containing the RS 30-35 centipoise type. The lacquer based on the RS 18-25 centipoise type was not improved by these changes. This indicates that RS 30-35 centi-
522
poise nitrocellulose probably represents the lowest viscosity material that can be used in lacquers of this general type without sacrificing cold-check resistance. A comparison of data for formulas 6 and 7 (Table 111) with data for the commercial lacquers indicated the following pertinent facts: The average nonvolatile content of 29% was 26% greater than the average (23%) of the three commercial lacquers. The cold-check resistance of formulas 6 and 7 was much better than that of commercial compositions B and C, and experimental lacquer 6 compared favorably with commercial lacquer A in this respect. Print resistance of the experimental lacquers was superior to that of any of the commercial compositions. Both Sward hardness and sanding of theae experimental lacquers was slightly better than the commercial compositions. Water-spot resistance was alike for all lacquers tested. LITERATURE CITED
Gardner, H. A,, "Physical and Chemical Emmination of Paints, Varnishes, Lacquers and Colors", 9th ed., p. 117, Washington, Inst. of Paint and Varnish Research, 1939. Koch, Wm., Phillips, H. C., and Wint, Rufus, IND,ENG.CHEM., 37, 82-6 (1945). Lowell, J. H. (to du Pont Co.), U. S. Patent 2,291,284 (July 28, 1942). Rush, 11. A . , BUZZ. Am. Cemm. SOC.,14, 365-7 (1935). PRESBNTED on the program of the Division of Paint, Varnish, and Plastics Chemistry of the 1945 Meeting-in-Print, AMERICAN CHEMICAL SOCIETY.
Asbestos as Filter Aid in
Sugar Refining TOH LIU China United Sugar Refining Company, Neikiang, China
A
F T E R Japan seized the Burma Road, the China United Sugar Refining Company, largest modern sugar refinery in free China, was confronted with the problem of carrying on its filtration processes without the necessary filter aid and filter cloth from abroad. An attempt was made to filter sugar sirups through the remaining supply of imported filter cloth without filter aid, but the flow rate was so low as to render the operation practically impossible. Chinese filter cloth, not so thick or so closely woven as the imported varieties, was then tried; the result was a higher rate of flow, but the filtrate was too turbid to yield a satisfactory product. At this point, the author was called in as consultant. From previous experience in filtering starchy materials, asbestos seemed to be the solution of the difficulty. I n the district where this plant is located, asbestos is abundant
and comparatively inexpensive; furthermore, for sugar refining only the cheaper grades are needed, which consist of various short fibers left when long, uniform fibers are prepared for other applications. Repeated tests have shown that asbestos not only incre:ses the flow rate enormously, but also clarifies and partially decolorizes the sirup by adsorption. *During the early part of the investigation, this company's practice of constant-pressure filtration was followed in order that the tests be made under plant conditions; i.e., a pressure of 50 pounds per square inch was applied a t the @art of filtration and maintained constant throughout the run. It wm soon found, however, 'that better results could be obtained by constant-rate filtration with the pressure gradually raised to 50 pounds a t the end of the operation; a still better procedure was to combine
Imported filter aids (such as Filter-Cel, Hyflo Super-Cel, etc.) had not been available in China since the spring of 1942, so that locally produced asbestos was used as a substitute in sugar refining. Asbestos increases the flow rate and reduces the turbidity and color of the sirup when mixed with the sludges to be filteted. Filtration pressure has a profound influence on the flow rate and clarity; 0.3% asbestos on the weight of raw sugar, together'with careful pressure control, can raise the clarity of sirup
85% and the flow rate at least 943%; a larger proportion of asbestos would undoubtedly have a greater effect under similar conditions. Chinese elt'er cloth may be substituted for imported types in filtering sugar sirups if asbestos is used as a filter aid to remedy the defects of the former. The asbestos in the filter cake can be recovered by washing and re-used several times. The sugar in the cake can be recovered by washing and used as a raw material for the manufacture of industrial alcohol.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
522 TABLE I.
Time, hlin. 5 10 15 20 25 30 35 40 45 50 55 60 Q
b
constant-rate and constant-pressure filtrations-first conetani CONSTANT-PRESSURE FII.TR.UIOSS WITHOCT FILTEX rate to ensure the formation of a good coating on the filter cloth .41D then constant pressure a t the maximum value during the rest ol Vol. a t 50 Lb./ T'ol. a t 30 Lb./ Vol. a t 20 Lb./ the operation. Sq. In., Cc. Sq. I n . , Cc. Sq. In., Cc. The laboratory data on filter aid and filtration pressuro M t r v In 5 In 5 In 5 min. Total min. Total rnin. Total put into practice in the refinery with highly satisfactory result 5 , both technically and economically. I t was expected that the filtration pressure procedure would be adhered t o even aftcr the war when other filter aids would become available again LABORATORY TESTS
Dropped practically t o zero in 2 hours. Clarity before filtration, 5.8 mm.
TABLE 11. INCREASING-PRESSURE (CONSTANT-RATE) FILTRATIONS WITHOUT FILTER AID To 20 Lb./Sq. I n . in 1 Hr. Vol., cc. '
Time, Min. 5 10 15 20 25 30 35 40 45 50
"?,/Bq' 1 1
2 2 4 4 6 6 10 10
15
55 60
20
T o 10 Lb./Sq. I n . in 1 Hr. Lb./sq. YOl., c e . in. I n 5 m i n . Total 1
I n 5 min. 1.6 1.2 1.4 1.1 1.3
1.0
1.0 0.7
1.1
0.8 1.0
0.9 Clarity,
Total 1.6 2.8 4.2 5.3 6.6 7.6 8.6 9.3 10.4 11.2 12.2 13.1 8.8 mm.
1
1 2 2 3 3 5 5 7 9 10
T o 10 Lb./Sq. I n . Pressure in 2 Hours--
Tirye, mln.
Vol. 38, No. 5
Lb,/sq. 1n.
5 10 15 20 25
"O'.,
I n 5 rnin. 3.0 1.9 1.6 1.2 1.8 1.6 1.2 1.1 2.6 2.2 1.9 1.7
30 35 40 46 50 55
GO
Total 3.0 4.9 6.5 7.7 9.5 11.1 12.3 13.4 16.0 18.2 20.1 21.8
Time, min. 65 70 75 80 85 90 95 100 105 110 115 120
Lh./sq. VO1.* cc. in. I n 5 min. Total 6 6 6 6 8 8 8 8 10 10 10
10
WITH 50 P o C N D S PRESSURE .4ND 0.3% TABLE 111. FILTRATIONS ASBESTOSON RAWSGGAR
Time, Min. 5 10 15 20 25 30 35 40 45 50 55 60
Increasing Pressure up t o 50 Lb., Cc. Vol., cr. I n 5 min. Total 2 6.2 6.2 11.0 4 4.8 16.0 6 4.0 18.8 3.8 8 22.3 3.5 10 26.4 4.1 15 30.3 3.9 20 33.9 3.6 25 37.3 3.4 30 41.1 40 3 8 41.4 3.3 50 47.2 50 2.8 Clarity, 12.9 mm.
T'ol. a t Constant Pressure of 50 Lb., Cc. I n 5 min. Total
Lb./sq. In.
The tests were made with a specially constructed prcssurc filter of the enclosed type. A circular filter disk, 1.48 inchcs (3.76 cm.) in diameter, was suspended inside a cylindrical shell of about 2-liter capacity, provided with the necessary feed inlet, filtrate outlet, pressure gage, hot water jacket, connection for compressed air, etc. American filter cloth, like that used in commercial filter presses, was used except in a few runs (Table VIII) where Chinese filter cloth was tried. Asbestos was purchased from Ta-chwan Asbestos Company in Chungking, screened to remove pulverized impurities, and cut into lengths of approximately 1 mm., either by hand-operated shears or by power-driven beaters. Before use it was weighed in cloth bags and repeatedly boiled and washed until t,ho water was clear, colorless, and neutral. The sugar sample was a native crude product with an average sucrose content of 88.25y0 by direct polarization. It was made into a sirup of 50 O Brix, heated with asbestos to about 80' C., and kept within the range 40"to 45 O C. duringfiltration. The volume of filtrate was read every 5 minwtes, and the filtration prcssurc adjusted when necessary. After each filtration, the color of the mixed filtratc m s wamincd in a pair of homemade colorimeters of the Hehncr type. Elaborate apparatus such as the Pulfrich photometer were 1111available for measuring thc clarity of filtrate. Therefore tlw author constructed a simple turbidimeter, similar to that, desrribed by Kopke (2). It consisted mainly of a graduated cylinder of uniform diameter with a plane bottom of polished clear glass, a fincprint card of high-grade white paper fixed on an adjustable reflector, and a wooden box with a hole in the top for holding the graduated cylinder. There was ample space inside the: box for fitting the adjustable reflector below the hole and a 100-watt coiled-filament lamp opposite the reflector. When the filtrate in the cylinder is adjusted to such a depth that certain letters on the card are made just visible by the light reflected through tho sample, the depth in millimeters may be taken as a measure of the relative clarity. Tables I t,o VI11 give rcsults of the testa, average valucx of a t least two runs under identical conditions in each case. DISCUSSION OF RESULTS
Thc tables show that, in filtering sugar sirups at, a const>ant pressure of 60 pounds per square inch, the addition of 0.3y0 asbestos (based on raw sugar) increased the flow rato 104% and the-clarity nearly 487& Filtering a t an increasing pressure T.4BLE I\*. FILTRATIONs WITH PRESSCRE UP TO 20 POUNDS AKD 0.3 TO 0,670 h B E B T O S (constant rate) with 50 pounds as the Vol. with 0.4% Vol. with 0.5% Vol. with 0.6% pressure, Vol. with 0.3% maximum, the flow rate rose 529% and the ~ i Lb. ~ per ~ Asbestos, , Cc. Asbestos, Cc. Asbestos, Cc. Asbestos, Cc. Min. Sq. In. I n 5 min. Total I n 5 min. Total I n 5 niin. Total I n 5 min. Total clarity, C117~.For the increasing-pressure 10.5 10.5 7.9 7.9 6.4 6.4 1 5.8 5.8 5 filtratioiis with 20 pounds as the maximum, 9.0 19.5 6.8 14.7 6.1 12.5 1 4.5 10.3 10 the flow rate was raised about 243, 392, 7.0 21.7 10.0 29.5 5.8 18.3 4.6 1&,9 2 15 6.4 28.1 .5,l 23.4 9.3 38.8 2 3.9 18.8 20 468, and 65OYO,and the clarity about 52, 9.8 48.6 6.8 34.9 5.5 28.9 4.1 22.9 4 25 57.4 6.0 40.9 5.3 34.2 8.8 3.6 26.5 4 30 66, 92, and 1147, by adding, respectively, 6.1 47.0 8.5 65.9 5.3 39.5 3.2 29.7 6 35 0.3, 0.4,0.5, and0.6%asbestosasfiltrraicl. 7.0 72.9 5.4 52.4 2.7 32.4 40 6 6.2 58.6 7.4 80.3 3.4 35.8 45 10 The increase in flow rate would be, rcspec6.3 5,O 63.6 86.6 5,O 54.8 2.6 38.4 10 50 5.5 69.1 6: 0 92.6 5.0 59.8 3.5 41.9 15 55 tively, 328, 514, 609, and 835%, and that 5.3 74.4 5 .,6 98.2 4.7 64.5 3.0 44.9 20 60 in clarity, 54, 68, 94, and 116%, compared Clarity, 14.6 m m , Clarity, 16.9 mm. Clarity, 18.8 mm. Clarity, 13.4 mm. with results of filtration without arhcstos at
2:;
4";:
May, 1946
-
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
a constant pressure of 20 pounds per square inch. When the pressure was increased to only 10 pounds, the gain in flow rate was nearly 193 and 391% and that in clarity about 54 and 85'34 by adding 0.3 and o.5y0asbestos, respectively. With the pressure gradually raised to 10 pounds in 2 hours instead of 1hour, the addition of 0.3 and 0.5% asbestos caused the flow rate to rise more than 194 and 393y0 and the clarity more than 72 and l O l % , respectively. In the test lasting 4 hours with pressure slowly brought up to and maintained at 50 pounds, the combined effect of O.3y0 asbestos and pressure control made the clarity 85% better and the flow rate a t least 943% higher than the results which could be attained without filter aid at 50 pounds constant pressure for the , same length of time. In the filtration through Chinese filter cloth (Table VIII) the clarity was increased as much as 100 or 153yo by using 0.3 or 0.5% asbestos, although the increase in flow rate was only 26 or 93%. The figures obtained from the colorimetric examination of the filtrates are not included in the. tables, since the colors of sugar sirups a t different clarities or turbidities cannot be expressed accurately by the relative readings of color comparators so simple as Hehner's ( 1 , 3,4 ) . However, the color intensity of sirup was considerably reduced by the addition of o,3Y0 asbestos, and this decolorizing effect became more pronounced when higher percentages were used. Everyone who saw the dark brown filter cake was surprised a t the adsorptive power of the asbeftos for coloring matter as well as for other impurities of the raw sugar. Asbesta powder, white clay, paper pulp, bagasse, and 'rice hull were also tried as filter aids. The results were not so satisfactory as those with asbestos fiber. Washed and boiled rice hulls (between 40 and 100 mesh) had practically no effect on the flow rate and clarity of sirup when used up to 0.5% on raw sugar, and the effect of bagasse was only slight when similarly tested. Paper pulp made of young bamboo did not improve the clarity, although it increased the flow rate as much as asbestos fiber. Almost equally efficient in raising flow rate was a high-grade asbestos powder, and next was a treated white clay; but both of them affected clarity adversely. Their finely divided and difficultly separable constituents penetrated the pores of the filter cloth and made the filtrate much more turbid than that of the control. In view of these facts, together with the compressibility, high specific gravity, low porosity, objectionabb impurities, or other drawbacks of the materials tested, asbestos fiber was selected as the filter aid for sugar refining during the emergency. FACTORY OPERATION
Plate-and-frame filter presses are used in this factory, and each has a total filter area of nearly 160 square feet. Data from the laboratory tests indicated that each press should be able to handle an average of over half a ton of raw sugar per hour of straight filtration, if operated under the same conditions as the 4-hour test. Trial'operations on the presses confirmed this prediction; in fact, better results have been attained in the factory, with two presses operated simultaneously a t a filtration temperature higher than that of the laboratory tests. The clarity of filtrate has been invariably higher than that in the test, chiefly because better filter cakes were formed in the presses than in the laboratory where the cake or coating, being submerged in the sirup, was often disturbed or deformed. Moreover, the filter cake built with the aid of asbestos fiber could easily be removed from the filter cloth a t the end of each cycle, whereas the slime deposited on the cloth in the filtrations without asbestos was extremely difficult to clean by scraping or spraying I n routine operations in the factory, the filtration pre3sure was nearly always applied in the same manner as the laboratory test of 4-hour duration, notwithstanding the fact that raw sugars with different cake-forming qualities sometimes made it necessary to modify the procedure to a certain extent. The amount of asbestos has been limited to 0.3y0on raw sugar for the sake of economy. This limitation was found advisable especially in those
523
TABLE V. FILTRATIONS WITH PRESSURE UP TO 10 POUNDS AND 0.3 OR 0.5% ASBESTOS
Time, Min.
Pressure, Lb. per Sq. In.
Vol. with 0.5% Asbeatos, Cc. In 5 min. Total
V O ~with . 0.3% Asbestos, CC. In 5 min. Total
10.1 9.3 8.0 8.2 7.3 7.3 6.5 6.9 6.4 6.6 6.7 6.0
10.1 19.4 27.4 35.6 42.9 50.2 56.7 63.6 70.0 76.6 83.3 89.3 Clarity, 17.4 m m .
6.1 5.7 5.1 5.5 4.8 4.4 3.9 4.2 3.5 3.6 3.5 3.0
6.1 11.8 16.9 22 4 27.2 31.6 35.5 39.7 43.2 46.8 50.3 53.3 Clarity, 14.5 mm. ~~~
~________~
WITH PRESSURE UP TO 10 POUNDS IX TABLE VI. FILTRATION 2 HOURSAND 0.3or 0.5% ASBESTOS
Time, Min.
5 10 15 20 25 30 35 40 45 50 55
pressure, Vol. with 0.3% ~b e~ Asbestos, Cc. Sq.' fn. I n 5 min. Total 8.0 1 8.0 15.0 7.0 1 21.2 1 8.2 27.0 5.8 1
60
11.3 21.8 31.2 39.9 49.1 57.6 65.6 73.0 81.9 90.2 98.0 105.0 113.6 121.6 129.1 136.0 144.0 151.8 l59,3 166.7 176.5 185.3 193.2 200.7 Clarity, 18.7 mm. 11.3 10.5 9.4 8.7 9.2 8.5 8.0 7.4 8.9 8.3 7.8 7.0 8.6 8.0 7.5 6.9 8.0 7.8 7.5 7.4 9.8 8.8 7.9 7.5
33.6 39.7 45.3 50.3 56.2 61.4 66.1 70.4 75.4 80.0 84.0 87.7 92.4 96.6 100.5 104.0 108.6 112.7 116.3 119.7 Clarity, 16 mm.
6.6 6.1 5.6 5.0 5.9 5.2 4.7 4.3 5.0 4.6 4.0 3.7 4.7 4.2 3.9 3.5 4.6 4.1 3.6 3.4
2 2 2 2 4 4 4 4 6 6 6 6 8 8 8 8 10
65 70 75 80 85 90 95 100 105 110 115 120
Vol. with 0.5% Asbestos, Cc. In 5 min. Total
lo 10 lo
(4 HOURS) WITH PRESSURE UP TABLE VII. LONGFILTRATION TO 50 POUNDS AND 0.3% ASBESTOS Time, Min.
5 15 20 25 30 35 40 45 50 56 60 65 70 75 80 85 90 95 100 105 110 115 120
,
Pressure V0l.V CC. Lb er' I! 5 Sq.' fn. min. Total 7.7 7.7 1
6.8 7.1 6.0 6.8 5.9 6.1 5.0 5.5 4.7 6.1 4.4
1 2 2 4 4 6 6 8 8 10 10 12 12 14 14 16 16 18 18 20 20 24 24
4.9
4.5 5.2 5.0 6.1 4.6 4.9 4.6 5.4 5.0 6.2 5.5
14.5 21.6 27.6 34.4 40.3 46.4 51.4 56.9 61.6 66.7 71.1 76.0 80.6 85.7 90.7 95.8 100.4 105.3 109.9 115.3 120.3 126.5 132.0
Time, Min.
Pressure, Lb. per Sq. In.
125 130 135 140 145 150 155 160 165 170 175 180 185 190 195 200 205 210 215 220 225 230 235 240
28 28 32 32 36 36 40 40 45 45 50 50 50 50 50 50 50 50 50 50 50 50 50 50
Val., C'.
I? 5 mm.
Total
6.6 138.6 6.2 144.8 6.6 151.4 5.7 157.1 6.2 163.3 5.5 168.8 6.6 175.4 6.0, 181.4 7.8 189.2 7.6 196.8 10.8 207.6 9.9 217.5 9.8 227.3 9.9 237.2 9.5 246.7 9.0 255.7 8.0 263.7 8.0 271.7 7.8 279.5 7.4 286.9 7.0 293.9 6.7 300.6 6.4 307.0 Clarity, 6.0 14.8 313.0 mm.
THROUGH CHINESEFILTER CLOTH TABLEVIII. FILTRATIONS
pressure, ~i~~ Lb. per Min.' Sq. In. In 5 1 1 10 1 15
20 25 30 35 40 45 50 55 60
2 2 3 3 5 5 7 9
10
Vol. without Asbestos, Cc. 5 min. Total
9.2 6.8 4.9 6.0
9.2 16.0 20.9 26.9 5.0 31.9 5.2 37.1 3.8 40.9 4.6 45.5 3.0 48.5 3.0 51.5 2.8 54.3 2,' 56.4 Clarity, 6.6 mm.
Vol. with 0.3% Asbestos, Cc. In 5 min. Total
'
Vol. with 0.5% Asbestoa, Cc. I n 5 min. Total
524
INDUSTRIAL AND ENGINEERING CHEMISTRY
cases where the raw sugar contained large amounts of impurities; when mixed with the asbestos, these impurities were likely to give trouble in the multistage centrifugal pumps used in feeding the filter presses. A whiter and more sparkling sugar could be produced by using more than 0.3y0 asbestos, but as little as 0.157, often made it possible to obtain a product good enough for the local market. The asbestos was always added to the sirup in a small mixing tank between the melting tanks and centrifugal pumps; the amount was divided so that the first batch or first h o batches of sirup got most of the total amount' of asbestos used, in order to produce an effect similar to precoating. K i t h raw sugar containing large percentages of solid impurities, high flow rate and pumping efficiency could be attained by using a precoating of asbestos in aqueous suspension, although clarification and decolorizing were usually more effective when the asbestos was thoroughly mixed with all of the hot sirup before filtration. The asbest'os in the filter cake could be recovered and re-used several times. It was most economically revivified by washing the filter cake, cither manually or mechanically, with four times its weight of warm water, then x i t h four times its weight of warm soap solution, and repeatedly with similar quantities of water
Vol. 38, No. 5
until they were clear and the asbestos free from sugar and colloidal matter. The first washing, xhich extracted over 85% of t,he sugap left in the cake, was used, together with final molasses, for the manufacture of power alcohol in the distillery attached to the refinery. ACKNOWLEDGMENT
The author wishes to express his gratitude to C. ?;. Shen, @. \Vu, and C. H. Huang, of China United Sugar Refining Company, for their kindness in placing all available facilities a t his disposal during the investigation. Thanks are also due to C. C. Chien, T . F. Wu, and S. C. Liu for their enthusiastic assistance in carry' ing out the experimental routine. James R. Withrow, of Ohio State University, very kindly handled the manuscript and checked proof, to save t,he long delay in transit to China. LITERATURE CITED
(1) Balch, R. T., IND.ENG.CHEM.,A N ~ LED., . 3, 1 2 4 (1931). (2) K o p k e , E. W., Facts A b o u t Sugar, 23, 177 (1925). ( 3 ) P e t e r s , H. H., and Phelps, E'. P., Bur. S t a n d a r d s , Tech. Papers, 338, 261-7 (1927). IND.ENG.CHEM.,ANAL.ED., 6, 178 (1934); 7. (4) Z e r b a n , F. W., 157 (1935) ; 8, lG8 (1936).
Moisture Adsorption of Textile Yarns at Low Temperatures ROBERT C. DARLING' AND HARWOOD S. BELDING Fatigue Laboratory, Harcard University, Soldiers Field, Boston, iMass.
T
H E fact that textiles between air and material a t T h e moisture adsorption of wool, cotton, cellulose acetake up and lose moise q u i l i b r i u m . Since all tate, and viscose rayon yarns was measured at +40", Oo, ture in rclation to the temworkers agree that the equiand -20' F. and at several relative humidities above 50%. perature and humidity of the librium points for adsorption The equilibrium values obtained, together with similar air has interested many and desorption are different, values at higher temperatures in the literature, indicate workers, not only because of the latter technique is subthat at constant relative humidity there is a high point the practical influence on ject t o the criticism that between 0' and 40' F., and that less water is bound at weight and insulation, but there was undoubtedly adlower as well as higher temperatures. The significance of also because of the light this sorption of excess on some% this finding in terms of possible changes of heat of adsorpproperty throws on the physifibers followed by partial drytion is discussed. Curves of the rate of w-ater adsorption cal chemistry of the maing of these fibers and transof the yarns are also presented, from which the over-all terials. The most complete fer to others. temperature coefficient of the process is derived. investigation of a variety of Wiegerinckestablished that, yarns was that of Wiegerinck up t o 212" F. a t constant relative humidity, there was a linear relation betwcen log moisture ( 1 2 ) . However, his emphasis was on high temperatures, the lomest temperature tested being 96' F. (35.6" C.). Speakman and content a t equilibrium and the reciprocal of absolute temperature Cooper (9), hovxver, carried the measurements on wool down to ( l / T ) . He presented this as anempirical relation, but others have 25' C. (77" F.), and Grquhart and Williams (11)on cotton down given their data theoretical significance by graphing them. Babbitt (2) reviewed and extended the theoretical treatment of the to 20" C. (68" F,). Several other workers, according to Babbitt ( 2 ) ,have studied purified and crude cellulose from cotton or wood data of others on cellulosc. He utilized the method employed by sources, but not below 20" C. Likewise the measurements of Bull Stamm and Loughborough (10) for calculating heat of adsorption (5) on a variety of proteins included those on wool a t 2.5' and from a graph of log pHpO against 1 / T and compared the values 40" C. (104' F.). The results of various workers are in fairly obtained with the direct measurements of Kata ( 5 ) and Argue and good agreement although the techniques differed somewhat. Maass (1). Bull (S),on wool and other proteins, calculated the Wiegerinck obtained true adsorptive values by a theoretically free energy change in full saturation adsorption as the area under better technique than that of Speakman and Cooper or Urquhart a curve of a/x against 2, where a represents grams of water adand Williams; he exposed the materials to a rapidly moving sorbed per 100 grams protein, and x is relative vapor pressure. stream of air of controlled temperature and humidity, whereas the From the free energy change a t two temperatures he calculated other workers exposed them in a chamber of still air with a known the heat of adsorption. I n these calculations either the variaamount of water vapor and measured the distribution of water tions in heat of adsorption with temperature are not discussed, or it appears that the heat of adsorption is essentially un1 Present address, College of Physicians and Surgeons, Columbia Unichanged over the temperature range studied. versity, N e i r York 32, N. Y.
