September, 1932
I N D U S T R 1.4 L A N D E N G I N E E R I N G C H E M I S T R Y
that is, by plotting the oscillation frequencies of the limits of the absorption bands against the logarithms of the relative thicknesses of the solutions (10). DISCUSSIONOF RESULTS As anticipated, the diketostearic acid is yellow, while the ketohydroxystearic acid is colorless. The position and the persistence of the absorption bands are clearly shown by the curves. The diketostearic acid has a well-defined absorption band in the blue end of the visible spectrum and shows the same light absorption characteristics as the diacetyl and the thymoquinone whose absorption curves are reproduced from Smiles ( 1 1 ) for comparison. The ketohydroxystearic acid shows a less pronounced selective absorption which, however, is entirely located in the ultra-violet region and, therefore, cannot produce visible color. Even the addition of an excess of alkali does not produce visible color. It is obvious, then, that the yellowing of oxidized drying oils be due to the presence Or formation Of ketohydroxy Of the problem in the The therefore, be sought in a different direction.
1043
ACKNOWLEDGMENT The authors wish to thank J. s. Long and J. G. SmuU of Lehigh University for the preparation and identification of the ketohydroxy- and diketostearic acids. LITERATURE CITED B a l y , “Spectroacopy,” 3rd ed., Vol. I, p. 117, Longmans, 1924. (2) E l m , IXD. ENG.CHEM., 23, 885 (1931); Paint V a r n i s h Prodiiction Munager, 30 (Sept., 1931); Qfiiciul Digest, 105, 474 (1931). E l m , ISD.ESG. C H E M . ,23, 886, literature cited (1931). (3) (4) Holde and Marcusson, Ber., 36, 2657 (1903). (5) Houben, “Die Methoden der organischen Chemie.” 3rd ed., P a r t I, p . 280, Georg Thieme, Leipzig, 1925. (6) Lewkowitch, “Chemical Technology of Oils, Fats, and Waxes,” 6th ed., Vol. I, p. 575, hlacmillan, 1921. (7) Morrell and Marks, J . SOC.Chem. Ind., 50, 27 (1931). ( 8 ) Morrell and Marks, I b i d . , 50, 30 (1931). (9) Smiles. “Relations between Chemical Constitution a n d Some Physical Properties,” pp. 324-423, John Long, London, 1910. (10) Smiles, Ibid., p. 329. (11) Smiles, I b i d . , pp. 372 and 374.
RECEIVEDApril 7. 1932. Presented before the Division of Paint and Varnish Chemistry at the 83rd Meeting of the American Chemical Society, New Orleans, La.. March 28 to April 1, 1932.
Moisture Sorption b.y Carbon Black CHARLES S. DEWEYAND PAUL K. LEFFORGE, Godfrey L. Cabot, Inc., Boston, Mass. G o o d w i n and Park also comH E s o r p t i o n of water The moisture content of carbon blacks is pared natural moisture with that vapor on carbon blacks dependent upon the concentration of water a t a low-temperature saturation. has received considerable vapor. The znriation, however, is not repreLeBlanc, K r o g e r , and Kloz attention from t h e p r a c t i c a l sented by Freundlich’s equation for adsorption, carefully determined the rate of standpoint. There is, in addinor by simpler straight-line functions such as moisture sorption for a variety of tion, a definite relationship beblacks. Their samples were extween m o i s t u r e sorption a n d Henry’s law. The isotherms are generally S posed in shallow layers. In 15 other chemical properties of this shaped, varying widely f r o m slightly irregular to 20 minutes they acquired apmaterial which as yet has relines io the accentuated curves f o u n d with acproximately half of the increased ceived scant public a t t e n t i o n . t icated charcoal. water content whichwasobserved This relationship can be indiA210isture sorption data obtained with cona t equilibrium after 4 to 5 hours. cated by a comparative study of A more a c c u r a t e study has various carbon blacks and other trolled humidity can be definitely correlated to been indicated by Wilson and carbons, such as lampblack and other adsorption tests f o r both carbon blacks and Fum-a (34, who r e p o r t e d the activated charcoal. charcoal. They are readily reproducible, and moisture content of various maThe practical significance of indicate the practical possibilities of this adterials for a large range of humidimoisture c o n t e n t was emphasorption indt>x. ilpplication to trade requiresized by Johnson in 1928 (17). ties. They found that carbon black (for rubber) took up 6 per He called the attention of the ments in pigment carbons m a y be developed by rubber industry to the effect of cent water when a t equilibrium a n expansion of this study. atmospheric humidity upon the in an atmosphere of 90 per cent humidity a t 25” C. Activated m o i s t u r e content of custompacked carbon black. He showed that the weight of water in- charcoal under the same conditions contained 33 per cent side a packed sack varied with changes in air conditions, corn- water on the dry basis. ing to an equilibrium with any continued condition after The reverse effect-that of removing water from carbon several days. black by means other than heat-is mentioned in the literaThe sorption on carbon black of water vapor from a satu- ture less frequently. S e a l and Perrott studied this, as noted rated gaseous phase has been reported by Neal and Perrott above. LeBlanc, Kroger, and Kloz dried their samples for ( 2 4 , Wiegand and Boggs (52), Goodwin and Park ( 1 4 , and saturation study over phosphoric anhydride. Moisture adby LeBlanc, Kroger, and Kloz (19). The conditions covered sorption and desorption (the term “sorption” is used in this have varied from thermostatic room-temperature control paper to represent the acquisition and retention, by various to storage in an ice box. Kea1 and Perrott reported initial materials, of moisture in equilibrium with water vapor, except moisture a t a natural humidity of about 60 per cent, loss in when modifying ideas are to be expressed) on charcoal have weight by drying over sulfuric acid, and moisture regain over been carefully studied by many investigators, notably by water, all a t 25” C. Wiegand and Boggs refer to a “moisture Lowry and Hulett (20-22), Coolidge (9-11), and Allmand and index” which seems to correspond roughly with their di- eo-workers (1-3). phenylguanidine and potassium hydroxide adsorption indices. In contrast with charcoal, apparently little work has been
T
1046
IYDUSTRIAL AND ENGINEERING CHEMISTRY
done on the sorption of organic solvent vapors on carbon black. LeBlanc, Kroger, and Kloz ( 1 9 ) , corroborated by Goodwin and Park (14), have indicated the extent to which the sorption of solvents may interfere with analytical adsorption tests. Firth (13) and Gordon and Krantz (16) have indicated a similar effect of water in the adsorption on charcoal of iodine from organic solvents.
FIGURE1. DIAGRAM OF HUMIDITY CABINET
There are available in the literature several reports which present the adsorption of chemical reagents by carbon blacks in liquid media. Iodine adsorption (5,8,14,18, SO) has been reported most frequently, followed by that of organic accelerators (8, 14, 18, SO), such as diphenylguanidine, mercaptobenzothiazole, and hexamethylenetetramine, and by potassium hydroxide (32). The adsorption of dyes (14, 30) (such as methylene blue, malachite green, and victoria blue), of sulfur (8, 18), and of benzoic acid (8) have also been described. Carson and Sebrell (8) have described the reaction, or interaction, of adsorbed material with zinc oxide and sulfur. Johnson (18) has used zinc dust for a similar study. Carson and Sebrell (8) indicated that data for iodine conformed to Freundlich's adsorption requirements. Trividic (31) has shown this to be true for charcoal, although Page (25) concluded that the curve is parabolic. Goodwin and Park (14) published corresponding adsorption curves for iodine and for methylene blue on carbon black, but stated that these did not conform to Freundlich's formula. A similar dependency of the adsorption figure on the end concentration undoubtedly holds true for the organic accelerators which have been used in adsorption tests, according to information available in the Cabot laboratories and in recent papers by Drogin (12) and by Wiegand and Snyder (34). Other tests, such as those concerning zinc oxide already mentioned are found to be dependent upon chemical action. The oxidation of carbon black by potassium permanganate has been reported by Beaver and Keller ( 5 ) . This reaction appears to take place more readily and extensively with carbon blacks of a comparatively high volatile content. The majority of papers on carbon black emphasize the relationship between analytical or physical properties of this pigment and the effect of the material in a rubber mixture. Thus, Beaver and Keller (6) noted the effects of high oxygen content in carbon black on rubber properties, but disclaimed any relationship of these properties to iodine adsorption tests or color intensity. Goodwin and Park (15) stressed the close relationship between adsorptive properties and the characteristics of rubber mixtures. Carson and Sebrell (8) showed that, among normal channel blacks, higher iodine adsorption was accompanied by slower cure in rubber, but that there were unexplained exceptions. Johnson (28) emphasized the relationship between accelerator adsorption, oxygen and volatile content, and curing rate, but coniirmed the earlier disclaimers of indicative relationship between iodine adsorption and the other properties. Parkinson, however, has reviewed many of these tests, and has em-
Vol. 24, No. 9
phasized the apparent relationship between particle size, black color intensity, and the adsorption indices (26). Particle size and adsorptive activity are, of course, both related to surface area in a pulverulent material (4). In this paper it is not planned to deal exhaustively with internal carbon structure nor to speculate on the relationship between adsorptive or other analytical properties of carbon black and the effects in rubber induced by the various commercial types. It is rather to present a new adsorption index for this type of material, and compare it to those already known. Moisture sorption, as well as other adsorption characteristics, undoubtedly reflects a complexity of factors in the carbon particle. Surface area and activity (as represented by residual volatile material) and hydrophillic nature (as indicated by oxygen content and possibly by inorganic impurities) should cover the range of essential factors involved in a study of carbon black properties. Neal and Perrott (24) and Johnson (18) have already pointed out the coincidence of high volatile content and hygroscopicity in carbon blacks. The presence of combined or adsorbed carbon dioxide, considered by Miller (23) and others as important in tests with activated charcoal, may be of importance in carbon black studies for different reasons. Volatile material may be induced or residual. The induced type arises from the sorption of oxygen. According to Rhead and Wheeler (E?),this sorption is widely variable in mode and in the resulting properties of the product. It is,
TLme
Of Exposure In
Hours.
FIGURE2. RATES OF MOISTUREVAPORADSORPTION AND DESORPTION ON CARBON BLACKSAT 37.8' C . (100' F.)
broadly speaking, oxidation, and gives rise to gaseous products and to a n indefinite solid product, CzOy, as well. Induced volatile content of carbon blacks-i. e., in excess of that found in the normally produced material-has been described by Johnson (18) and by Plummer (28). Allmand and Hand ( 2 ) , after reviewing the papers of several workers, have suggested that even room-temperature oxidation causes a change in adsorptive properties of activated charcoal. The residual volatile matter is that available by thermal decomposition to a residue of carbon of those condensed hydrocarbons deposited in, and part of, the original carbon char. These hydrocarbons constitute an important part of all potential activated carbons, as outlined by Lowry (20). Lowry also pointed out the close relationship between hydrogen content and sorptive capacity toward water. Fundamentally no adsorption test on carbon is a true indication of adsorptive properties, unless applied to material which has been totally devolatilized a t a low temperature. Commercial application, however, involves the whole carbon black compound as manufactured, and most analytical studies for control purposes must be undertaken without special preparation of the material. Practically, adsorption tests
September, 1932
I N D U S T R 1.4 L :I X D E N G I N E E R I N G C H E M I S T R Y
a s we know them are rendered too complex by the various chemical and physical factors involved for us to be able to evaluate them completely. Every nex and clear-cut variaE,
/ I
1
1-
/
/
,i:
4
1047
not be controlled entirely by preheating the air. This was, however, accomplished easily by adjusting the room temperature when it was more than a few degrees off. The actual moisture content of the air was determined by measured aspiration through a small calcium chloride tube (le) by means of a bleeder inserted in the cabinet. A supplementary control was also obtained by a frequent similar withdrawal through a small dew-point bottle (lj). TABLEI. COMPARISON OF METHODS OF MOISTURE DETERMINATION
a
SAXPLE
NITROQEN SWEEPINQ Temp. Results c. % 1.40
3
VAPOR PRESSURE
IN MILLIn-IETERS.
SORPTION FIGURES 3 TO 5. MOISTURE ISOTHERMS FOR C A R B O N BLACKS AT 37.8' C. (100' F.)
105' C. DRYINQ BOILINQ OVEN XYLENE % % 1.38 1.4
3.90 3.82
....
... ...
Approximately 1.5 grams of each of the samples to be studied were placed in a uniform layer in a 45 X 25 mm. weighing bottle. The average sample of carbon black was thus about 5 mm. deep. When sorption rates were to be determined, the samples were all exposed overnight to dust-free air of the desired initial humidity in order that they should be in comparable condition a t the start. For small humidity changes the samples were exposed in the cabinet for 4 hours, weighed, and reexposed a further 2 hours to prove equilibrium attainment. Longer treating periods were used whenever necessary, as indicated by the results of these first two weighings. After the data for several humidity changes had been acquired, the samples were placed in the 105-110" C. drying oven for 2 hours to obtain the dried base weight.
48.4 mm. vapor pressure represents saturation: 42.5 mm. represents 88 per cent humidity--
the highest controlled humidity used.
tion, such as moisture sorption, adds t o our knowledge] and mill eventually assist in developing effective control criteria of carbon blacks.
TESTSBY FLOW METHOD The flow method with controlled humidity m s chosen as more practical than the static vapor or desiccator methods, where, as in this case, a large number of samples was to be studied. The humidity cabinet (Figure 1) was iin insulated box, 100 cm. long, 50 cm. wide, and 30 cm. high (40 X 20 X 12 inches), supplied a t one end with a screen bottom drawer (la) for holding the samples, and a t the other end with the conditioned air inlet. The air conditioning system was composed of a supersaturator (maintained roughly a t a temperature 3-5" C. above the final dew-point requirements) and a strippingcoil thermostat for readjusting the saturation temperature. A semi-automatic heating box ( l b ) a t the cabinet inlet was controlled in part by a thermoregulator (IC), and in part by a hand-operated by-pass valve ( I d ) . All connecting lines were insulated. In addition, provision was made for warming them externally whenever operation a t high humidities made condensation a likely source of error. I n operation, compressed air was filtered through cotton, bubbled through the water in the supersaturating tower, and passed through the controlling unit and the cabinet a t a rate of approximately 2 cubic meters per hour (1 to 1.5 cubic feet per minute). The temperature control of the air in the controlling unit was maintained within 0.2" C. The cabinet, because of its large heat capacity and the slow air flow, could
Vapor Pressure. rnm. Mercury at 21° C.
FIGURE6 . MOISTURESORPTION ISOTHERMS AT 21" C. (70" F.) FOR TYPICAL SAMPLES M a represents saturation pressure.
Doubt has been expressed by Carson (7) as to the propriety of this method in determining true water content. It has been found, however, that it compares in results with that of dry nitrogen sweeping in a low-temperature tube furnace, and that of toluene distillation with a Stark and Bein tube. In addition, it is capable of greater accuracy and closer checking of duplicate runs than is the latter, and is more convenient than the former in dealing with a number of samples. In further confirmation of Plummer's conclusions (37) negligible differences in results were observed in many cases, when the
INDUSTRIAL AND ENGINEERING
1048
determination of moisture under nitrogen was carried out with temperatures up to 300" C. and over (Table I). On the other hand, Allmand ( I ) and Brown (6) have found that appreciable quantities of water are retained by activated charcoal under ordinary drying conditions. This phenomenon has been generally attributed to inorganic impurities. I n view of a variety of preliminary tests on carbon blacks, it is believed that any error of this type will not influence the practical nature of the results. I n contrast to most work on charcoals, the samples reported in this paper had been freely exposed to air, and would presumably hold water less tenaciously than freshly activated and out-gassed charcoals.
P Q R
S
T U
Vol. 24, No. 9
CHEMISTRY
Commercial lampblack low in oil content. Commercial furnace process carbon. = Commercial activated charcoal, reduced to 40 mesh. = No. M, oxidized in air at 40@-500° C. according to Plummer (28). = No. S, partially devolatilized by heating a t 600-700° C. u-ithout air. = Yo. T, extensively devolatilized by continued heating without air. = =
The comparative tests in moisture sorption have been limited to the range of humidities below 90 per cent. The saturation values, obtained by the static method with a much longer exposure, are included in the data tables and the isotherm curves. For the reduced isotherms the basic sorbed moisture concentration for each sample is taken as that found a t the highest controlled humidity used-i. e., about 88 per cent. The moisture content a t saturation is ignored, in view of the variation in method. TABLE11. EQUILIBRIUM MOISTURE.4ND 1
2
3
4
6
5
EQUILIBRIUM MOISTURE,
-4NALYTICAL 7
DATA 8
37.8' C . (100' F.)n At At 16.5 mm. 43 mm. .4DSORPTIOb TESTS Iodine D. P. G.e (33% (88% In rn SAM- huhuStatic MOISTURE VOLATILE .> .__ .-. PLE midity) midity) satn. RaTIob CONTENT ' water bensene
%
%
%
%
%
%
%
2.77 3.18 4.12 4.46 5.49 6.23
15.4 18.8 16.0 14.1 11.4 18.2
0.650 0.850 0.718 0.755 0.445 1.24
3.75 4.05 5.38 7.20
26.3 46.2 51.6 71.4
1.06 1.46 1.70 3.88
9.10 12.11 12.90 13.50
29.7 29.4 45.0 38.1
3.45 6.10 7.00 7.52
20.55
27.7
9.12
R U B B E R BLACK
A
1.30 1.72 1.46 1.89 1.76 2.56
2.36 3.28 3.42 3.54 2.88 4.55
2.95 5.00 5.09 4.86 3.56 5.98
2.12 1.83 1.85 3.26
5.00 6.49 7.36 15.7
8.35 13.0 13.4 18.1
L
M N
5.11 5.44 6.15 6.15
9.00 10.6 14.0 17.1
13.4 17.8 17.7 20.1
0
6.16
16.9
25.1
E
Volatrle Gontmt In Percent. FIGURE7. EQUILIBRIUM MOISTUREAT 33 PER CENT HuMIDITY AND 37.8" c., REFERRED TO VOLATILE CONTENT
C D E F
INTENSE INK
G
In order to approximate the time necessary for reaching equilibrium, five of the samples were first subjected to rate determinations for different humidity changes, both at 21.1 " C. (70' F.) and a t 37.8" C. (100" F.). The weights of moisture found at hour intervals for the 37.8" C. (100' F.) run are shown graphically in Figure 2 ( A , B, C). Separate trials (not recorded) indicated that the final changes were considerably slower at 70" F. for the same humidity ranges. Accordingly, 100" F. (37.8" C.) was taken as the standard operating temperature, with a smaller amount of data at 70" F. presented for comparison. The rate curves show that carbon blacks of lower capacity approach equilibrium in 2 to 3 hours under the same given conditions. Higher capacity carbons require 5 hours in the 70 per cent humidity range a t 100" F., but a considerably longer time in the 30 per cent range. The data recorded for some of the comparative determinations in this paper required an exposure time of 12 to 15 hours. The rates in any case are so rapid a t the start that analytically accurate weighings of samples are impossible unless the atmospheric exposure of the transfer and weighing operations approximates the effective humidity of the sample stock container. Frequently the balance adjustments observed in the laboratory shift continually while weighing uncovered samples. DATAON MOISTURE SORPTION Various carbon blacks used by the rubber and ink trades were supplemented for this study by a few unusual types of carbon, and by a small assortment of experimental samples. Except as noted, the samples were used as received without any pretreatment beyond mixing: ,
A-F = Commercial channel carbon blacks for rubber. GJ = Commercial channel intense black carbons for enamels
and lacquers.
K-N = Commercial roller process "long" ink blacks, = Waste soot from channel plant. 0
0.375 0.312 0.300 0.413 0.470 0.437
H I J
0.312 0.217 0.188 0.117 LOXG INK
K
0.414 0.404 0.263 0.272 SOOT
0.317 LAMPBLACK
P
2.43
3.49
4.14
0.610
4.45
4.82
0.373
0.35
3.68
0.130
FCRIACE
Q
0.00
0.70
2.89
(0.160) CHARCOAL
R
0.72
31.9
35.1
0.013
2.58
105.0
0.675
EXPERIMENTAL Q R O U P
M
14.0 17.7 6.15 33.2 63.0 5.83 29.0 2.68 51.0 17.8 45.4 u 0.80 Data are in terms of grams per cent dry basis. b k t 37.8' C . and,11.5/31 mm. c Diphenylguamdme.
S
T
0.263 0.156 0,074 0.046
12.90 18.40 10.80 1.72
45.0 72.9 89.1 107.7
100 grams of dry sample-i.
7.00 14.9 6.90 2.26 e . , in per
The data may be influenced by hysteresis effects. All. mand, Coolidge, and others have emphasized this feature in connection with charcoal work. The rate cuwes shown in Figure 2 indicate that the error is small for carbon blacks. The data reported in Table I1 are generally comparable for the different humidities, in that the data points, except the highest, were determined successively in desorptive order on the given samples. Several data points were also determined in the adsorptive order. These were used as checks in the establishment of accepted equilibrium data, in conjunction with a thorough study of the time Curves. The figures in Table I1 thus represent the original data from uniformly conducted determinations, corrected by an interpreted extrapolation of the time curves. The data isotherms for 100' F. (37.8"C.), shown in Figures 3 to 5 , present a considerable variation in shape for the various samples, in addition to a wide range in capacity. The ex-
September, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
tremes of shape are shown by activated charcoal a t one end and by lampblack a t the other. Over the whole series they bear little connection to actual moisture content a t any single chosen humidity. The data isotherms for TO" F. (21.1" C.) cover fewer points, and accordingly are lacking in curve detail. However, they show the same general trend as those a t 100" F. (Figure 6 gives typical examples) and the same capacity for moisture under similar conditions of relative humidity. This i n d e p e n d k n c e of t e m p e r a t u r e also exists in the saturation results obtained by the static method. D u r i n g these d e t e r m i n a t i o n s the temperature in the saturator cabinet, was varied slowly up and down b e t w e e n 70" a n d MQISTURE AT 100" F. without apPB% H U M I D I T Y . preciatile change in t h e gross s a m p l e weights. The high saturation v rt l u e s , abnormal with res p e c t t o the controlled d a t a curves f o r t h e s a m e materials, are striking. FIGURE8. CHANGE OF PROPERTIES OF S u c h abnormality CARBON BLACKWITH HEATING has also been noted .&I. Initial state of sample in work with charS. Sample after heating in presence of air, T ,1'. Results of heating S in absence of air coal (9). (Numbers within the chart represent proporIn Table 11, coltional change of index caused by heating a t each stage.) umns 2 to 4, the actual sorbed moisture for saturation and for two picked humidities is given. These values are compared to volatile content, assuming this to be the most stable reference property. The samples are grouped according to their commercial interest, and are arranged within the groups according to their volatile contents, excepting sample &. The graphical presentation (Figure 7 ) shows a considerable linear relation of sorption a t low humidity (33 per cent) to volatile content, as pointed out by previous workers (18, 24). This relationship is less apparent for moisture a t high humidities (88 per cent), although abnormal data a t high humidities are frequently accompanied by an opposite variation a t low humidities. The volatile content was determined in a manner similar to that for coal. One gram of sample wm weighed into a 15-cc. platinum crucible, and the capsule cover fitted in loosely. This was dried t o constant weight in an oven at 110" t o 120" C. The cover was then pressed firmly into place, and the crucible placed in a Fieldner furnace for exactly 7 minutes. The temperature regulation was uniform for all determinations, the actual maximum crucible temperature having been estimated at 943" C. (1730' F.). The crucible was weighed after being cooled in a definite fashion, and the volatile content calculated in terms of the dry weight of the undevolatilized sample.
1049
paper, although these two indices betray some similar tendencies. These adsorption tests were of a conventional nature. For the iodine adsorption, 1.0 gram of carbon black was shaken with 100 cc. of 0.lON iodine solution. In the diphenylguanidine test the solution used was 0.001 N in benzene. For the less active samples of carbon, 1.0 gram was used with 100 cc. of the diphenylguanidine solution. For the more active materials, a smaller weight was taken. The back titration data were calculated to per cent by weight of reagents adsorbed. A certain amount of tolerance is essential in comparing adsorption data, such as for iodine, with those for moisture, on account of the irregular and nonpredeterminable end concentration inrolved in the former seriep of tests. It must also
. I
The adsorption of diphenylguanidine and of' iodine are presented in columns 7 and 8 of Table 11. When plotted separately against volatile content, all but two of the diphenylguanidine data points fall within a narrow band. This index is, however, unlike that for low humidity moisture, in that the relation with volatile content is not linear, but logarithmic. There is apparently no simple coniparison for iodine adsorption, or for moisture a t high humidity (88 per cent) with any of the other analytical tests covered in this
FIGURES9 AND 10. REDUCED MOISTURE IsoTHERMS (ISOTHERM SHAPEAT 37.8' C. REFERRED TO UNITYAT 88 PER CENTHUMIDITY) Curves X re resent data on moisture sorption by aoti"ate{ charcoal, as reported by Coolidge.
be acknowledged that the exactness of such a comparison depends on the combined errors of all the analytical tests involved, referred to the closeness in scale (volatile content) of those samples under examination.
COMPARISON OF ADSORPTION INDICES When the adsorptive indices for different samples are compared with respect to the volatile content, the variation of equilibrium moisture for 88 per cent humidity from a hypothetical linear functional line analogous to that for 33 per cent humidity is found to be roughly an average of the variations of the iodine and diphenylguanidine indices. For example, with the widely wrying samples B, H , L , and R , the ratios of the various indices are as follows: IXDEX Volatile content Moisture a t 33% humidity Diphenylguanidine adsorption Moisture a t 88% humidity Iodine adsorption
L/H 2.99
2.96 4.20
1.64 0.64
H/B 1.2:
1.06
1.72 1.97 2.46
H/R 1.57 2.54 2.18 0.20 0.44
Thus the intermediacy of the shift of 88 per cent humidity with respect to iodine and diphenylguanidine adsorptions is shown for the carbon blacks. The slight abnormality of that index for charcoal (R) might be expected from the opposite irregularity of that for 33 per cent humidity as noted above-
INDUSTRIAL AND ENGINEERING CHEMISTRY
1050
i. e., the index a t 88 per cent humidity for H I R is 0.20 instead of some figure between 0.44 and 2.18, whereas the index for 33 per cent humidity ia 2.54 instead of approximately 1.57, in agreement with the shift in volatile content. Lampblack could not be correlated with the carbon blacks, probably b e cause of the oil content of the sample studied. The shifting of the indices due to thermal and oxidizing treatment is illustrated in Figure 8. (Wiegand and Snyder have discussed the various properties of deactivated blacks in recent papers, 33, 34.) The same remarks apply as with the preiious group of samples. Among these, M is the sample with which the indices a t 88 and 33 per cent humidity are out of line, but here also in opposite directions.
Vol. 24, No. 9
moisture sorption data. Moisture sorption (including isotherm shape) serves, however, as the first test to be reported by which three of the previously used tests can be correlated. It remains to be shown that the proper moisture index can be used directly in evaluating important practical features of industrial carbons. The data of these adsorption properties for carbon blacks have been compared with those for commercial activated. charcoal. The descriptive relationships of these indices, as noted for carbon blacks, apply also to charcoal. ACKNOWLEDGMENT
Acknowledgment is made to E. Billings, of Godfrey L. Cabot, Inc., for permission to publish the results of this investigation. The data for the diphenylguanidine and iodine adsorption tests were supplied by R. K. Estelow and E. H. Damon. LITERATURE CITED
0
5 Volatile Content
IO
Of Samples In Perccnt
15 By Weryht.
FIGURE11. COMPARISON OF IODINE ABSORPTION AND MOISTURE ISOTHERM SHAPEFOR MOREADSORPTIVE CARBONS
It is this distinction between adsorptive properties, including that of moisture, that points toward isotherm shape as of possible interest. The shape, in distinction to magnitude, is shown in the reduced isotherms (100’ F.) for representative samples of the various groups (Figures 9 and 10). This index-isotherm shape-is indicated numerically by the ratio of moisture contents found a t 24 and 62 per cent humidities (Table 11,column 5). The logarithm of this ratio (reversed) is plotted, coincident with iodine adsorption, against volatile content for all of the more active and a few of the less active carbon samples (Figure 11). This moisture ratio-i. e., isotherm shape-properly scaled, here shows a very close resemblance to iodine adsorption, whereas neither of these indices shows any simple relationship toward any of the other properties. It is a n interesting fact that the tests covered in this paper indicate a harmonious relationship of activated charcoal with the pigment carbons. The adsorptive characteristics of activated charcoal are closely approached by samples J (SuperSpectra) and U (devolatilized ink black). It is suggested that normal carbon blacks and charcoal represent a similarity in fundamental chemical constitution. They can all be described as belonging to a series of carbons distinguished by varying degrees of oxidation and activation. They contrast in the extent of activation, and in superficial physical structure. SUMMARY
Moisture vapor sorption is reported for a wide variety of commercial pigment carbons. This index of moisture sorption, when properly interpreted, harmonizes closely with the other adsorption figures for the same materials. The basic reference index for this comparison is volatile content. As is evident from an inspection of the charts and other data, no standard adsorption test for carbon blacks can be supplanted directly, or indicated simply, by any one item of
(1) Allmand, Chaplin, and Shiels, J . Phya. Chem., 33, 1151-60 (1929). (2) Allmand and Hand, Ibid., 33, 1161-6 (1929). (3) Allmand, Hand, Manning, and Shiels, Ibid., 33, 1682 (1929). (4) Bartell and Smith, IND. ENQ.CHEM.,21, 1102 (1929). (5) Beaver and Keller, Ibid., 20, 817 (1928). (6) Brown, Phys. Rev., 17, 700-6 (1921). (7) Carson, C. M., IND.ENQ.CHBM.,Anal. Ed., 1, 225 (1929). (8) Carson and Sebrell, IND.ENQ.CHEM.,21, 911 (1929). (9) Coolidge, A. S., J. Am. Chem. Soc., 46, 596 (1924). (10) Coolidge, A. S.,Ibid., 48, 1795 (1926). (11) Coolidge, A. S.,Ibid., 49, 708-21 (1927). (12) Drogin, I., I n d i a Rubber World, 83, No. 6, 57 (1931). (13) Firth, Trans. Faraday Soc., 16, 434-52 (1921). (14) Goodwin and Park, IND. ENQ.CHEM.,20, 621-7 (1928). (15) Goodwin and Park,Ibid., 20, 706-16 (1928). (16) Gordon and Krantz, J. Am. Pharm. Assoc., 13, 609-12 (1924). 22, 535 (1928). (17) Johnson, C. R., Rubber Age (N. Y.), (18) Johnson. C. R.. IND. ENQ.CHEM..21. 1288 (1929). LeBlanc; Kroger, and Kloz, KoEZbidc&m. Eeihefte, 20, 356-411 (1926). Lowry, H. H., J . Am. Chem. Soc., 46, 824-46 (1924). Lowry and Hulett, Ibid., 42, 1393-1408 (1920). Lowry and Hulett, Ibid., 42, 1408-19 (1920). Miller, Ibid., 46, 1150-8 (1924). Neal and Perrott, Bur. Mines, Bull. 192, 77 (1922). Page, J. Chem. floc., 1927, 1476-94. Parkinson, Inst. Rubber I n d . Trans., 5 , 263-83 (1930). Plummer, W. B., IND.ENQ.C H ~ MAnal. ., Ed., 2, 57 (1930). Plummer, W. B., IND.ENQ.CHEM,.22, 630 (1930). Rhead and Wheeler, Proc. Chem. SOC.,29, 51-3; J . Chem. SOC.. 1913,461-90. Spear and Moore, IND. ENQ.CHEM.,18, 418 (1928). Trividic, Rev. g6n. colloides, 7, 14-22 (1929). Wiegand and Boggs, IND.ENQ.CHEM.,22, 822 (1930). Wiegand and Snyder, Ibid., 23, 646-9 (1931). Wiegand and Snyder, Rubber Age (N. Y.), 29, 311-16 (1931). Wilson and Fuwa, J. IND.ENQ.CHEM.,14, 913-18 (1922). REC~XVE October D 30, 1931. C. 9. Dewey’s present address is Fireatone Tire and Rubber Company, Akron,Ohio: P.K. Lefforge’s present address ia Amarillo, Texas.
CZECHOSLOVAK PRODUCTION AND CONSUMPTION OF RAYON. Domestic production of rayon in Czechoslovakia is inadequate to meet the country’s consumptive requirements, and considerable quantities are imported, according to a report to the Department of Commerce. The local industry, which produces only viscose yarns, is protected b high tariffs and other restrictive measures which make possi&e a virtual monopoly of the domestic market, whereas imports are reported to consist mainly of acetate and cuprammonium yarns. At the end of 1931, the total productive capacity of the four rayon plants was said to approximate 4,000,000 kilos annually. The actual output, however, was estimated at 2,500,000 kilos in 1931, by a continental trade authority. Imports of rayon declined from 4,342,000kiIos in 1930 t o 4,190,000in 1931,while exports increased from 724,000 to 1,027,000.
