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(37) Schwarta, A. M.,and Perry, J. W., “Surface Active Agents,” pp. 31C-84, New York, Interscience Publishers, Inc., 1949. 1\38)Sialey, J. P. (translated by Wood, P. J.), Am. Duestuff Reptr.. 36, 457 (1947). (39) Snell, F. D., Chenr. Eng. S e w s , 27, 2256 (1949). 140) Utermohlen, W. P., J r . , Fischer. E. K., Ryan. 11. E., and Campbell, G. H.. Teztile Research J . , 19, 489 (1949). (41) Gtermohlen, W. P., Jr., and Ryan, M. E., IND. ENG.CHEW,41,
2881 (1949).
(42) Gtermohlen, W.P., JT., and Wallace, E. L., Textile Reseccrch J . , 17, 670 (1947). (43) Valko, E., “Kolloidchemische Grundlagen der Textilvered-
Vol. 42, No. 7
Vaughn, T. H., and Smith, C. E., J . Am. Oil Chemists‘ SOC.,25, 44 (1948). (47) Vaughn, T. H., Vittone, A , , Jr., and Bacon, L. R., IND. ENG. CHEX,33, 1011 (1941). (48) Vickerstaff, T., Am. Dyestuf Reptr., 38, 305 (1949). (49) Wiegand, W. B., IND.ENG.CHEM.,29, 953 (1937). (50) Williams, E. T., Brown, C. B., and OaMey, H. B., “Wetting and Detergency,” 2nd ed., pp. 163-74, New York, Chemical Publishing Co. of T.Y.. Inc., 1939. (51) Woodhead, J. A., Vitale, P. T., and Frantz, A. J., Oal & Soap, 21, 333 (1944). (40)
lung,” pp. 581-646, Berlin, Julius Springer, 1937.
(44) Van Zile, B. S., Oil 6: Soap, 20, 55 (1943). (45) Vaughn, T. H., Hill, E. F., Smith, C. E., McCoy. 1,. K., and Simpson, J. E.. Ixn. ENG.CHEX, 41, 112 (1949).
RECEIVED S o v e m b e r 21, 1940. Presented beforc t h e Division of Colloid hleetinf of the A\rE:Rrcas CtrshrIcAL SOCIETY, Atlantio City, N . J.
Chemistry at the 116th
(Some Physical-Chemical Aspects of Cotton Detergency)
CATIONIC ADSORPTION AND EXCHANGE AS SHOWN BY RADIOCALCIUM TRACER STUDIES JOSEPH AI. LAMBERT Central Research Laboratory, General Aniline & F i l m Corporation, Easton, P a .
s o m e of the physical-chemical properties of cotton responsible for the complex interactions in practical detergency have been reviewed. The accessibility and acidic characteristics of cotton appear to be of particular importance. The role of adsorption as an important factor in detergency is illustrated by experimental adsorption data of surface-active agents on cotton. Radioisotope tracer methods are described for measuring the adsorption and exchange of calcium on cotton as it occurs in laboratory wash tests simulating hard water laundering. Results are presented which were obtained with several cotton detergents in multicycle wash tests. Varying amounts of calcium are adsorbed depending on the detergent and on the condition of the cloth (new or used cotton). -i tentative interpretation of these effects is offered as well as a discussion of possible extensions of the method.
I
S T H E preceding paper (bo) it was demonstrated that vcry
small quantities of ingrained soil, which are not removed from the cellulose fiber, play an important role in practical cotton detergency. It was also shown that the inaccuracy of present testing methods has led to many discrepancies between the evaluation of detergents in the laboratory and their performance in actual use. For further technological advances in this field which might lead t o greatly improved products, a more rational basis of cotton detergency t,esting has been considered essential. I t is also generally agreed that a better understanding of the washing mechanism would help in the formulation and possible solution of the problem. One of the important materials in cotton detergency is no doubt t,he cellulose fiber. Therefore, it was thought worthwhile to review first the physical and chemical properties of cotton and to search for a laboratory test which would measure some of the complex interactions between bath components and the fabric in the washing process. PHYSICAL CHEMISTRY OF COTTON
Cellulose chemistry, as one of the major branches of chemical scirnce and technology, has been a field of most intensive investigation; therefore, only a cursory review of some of the aspects pertinent to detergency can be given here. The chemical
and physical properties of native cellulose have been describetl extensively in monographs ( 1 2 , 14,28) as well as in the recent literature (4,16, 17, dZ, 24, SO, 43). Of particular importance for the understanding of the spatial aspects of soil retention arc: the fibrillar structure of the cotton fiber and the intermicellar hole and tube system as described by Mark ($4)and shown in electron micrographs by Kinsinger and Hock (17). Although the interaction of the colloidal soiling materials with the fiber might be expected to take place predominantly in the amorphous domains, accessibility in the physical and chemical sense will also influence that interaction. The chemical accessibility has been shown to be an exact experimental quantity which can be det,ermined by D20 exchange ( 2 , 1 ) or water sorption (16) experiments. The acidic properties of cotton cellulose have been studied by Sookne and Harris ( 3 6 ) who used a number of different techniques. By testing carefully prepared dewaxed and depectinized cott,on, these authors proved that many of the acidic characteristics of cotton are due to the pectic substance. However, the residual base-combining capacity of their highly purified and electrodialyzed cotton samples lead them to the conclusion that the acidic groups may be an integral part of the cellulose itself. In view of the slow, but steadily progressing deterioration of the cotton fibers during normal use (3: 3 2 ) and laundering (26, $6, 29), the chemical characteristics of oxycelluloses appear to be of even greater importance. In recent studies on the acidic properties of cotton cellulose anti derived oxycelluloses, Davidson and Neve11 (6,6)have shown that cations are readily absorbed from aqueous solutions. They conclude that the characteristic properties of acidic oxycelluloscs are most easily explained by the assumption that an exchange of ions can occur on carboxyl groups. The ion exchange process is represented by the following reactions which lead to a state of equilibrium:
RCOOH
+ l,l+S RCOOLI + H +
where RCOOH represents an acidic oxycellulose and M +, the cation. Besides silver and calcium ions, methylene blue was found t o furnish a suitable cation for quantitative adsorption measurements on various celluloses. Also unmodified cotton having a low carboxyl content showed cationic adsorption partly attributable to hydroxyl groups. The foregoing experimental
INDUSTRIAL AND E N G I N E E R I N G C H E M I S T R Y
July 1950
results indicate t h a t even new cotton has acidic characteristics which will make it selectively more adsorptive for cationic oi otherwise positively-charged materials. ADSORPTION IN DETERGENCY
*
n
Although many factors which reportedly play a role in the detergency process have been enumerated and discussed (83, 35, 41), their relative importance has not yet been determined. Among the early investigators in the field of cotton detergency, Rhodes and Brainard (34) and Spring ( 3 7 ) considered the combination of the surface-active soap or detergent ion with the soil in the fiber of prime importance. I n this connection it is noteworthy that only the negatively charged anionic and suitably built nonionic, but not the cationic surface-active agents, have the property of washing cotton or other fabrics. This seems to confirm the contention t h a t the ingrained soil consists predominantly of positively charged colloidal matter. The importance of adsorption in the detergency process can be readily understood. While much of the natural soil in cotton might be superficial, a certain small amount of it is obviously embedded in the interior of the fiber. The surface-active agent will have t o penetrate, therefore, into the intermicellar regions for proper interaction with the ingrained soil. It follows that one of the important properties of an effective detergent is a definite affinity for the textile fiber which it is supposed to clean. A number of investigators ( 1 , 8, 19, 26, $7, 39) have studied the adsorption of soaps and surface-active agents in various systems. Tjutjunnikom and Pleschkowa (39) studied the displacing adsorption in soap solutions containing activated carbon snd a dyestuff in order to determine the cleaning properties of the various soaps. Neville and collaborators (26, 87) have studied both adsorption of synthetic detergents on wool and selective adsorption of soap on various fabrics and materials. Of particular interest in connection with cotton detergency is the work of Acharya and Wheeler ( 1 ) and Gardiner and Smith (8) who investigated the adsorption of soap on cotton. The former authors claim that a direct correlation exists between the amount of a particular soap adsorbed, and its cleansing power. A study was also made in this laboratory (19) in which the adsorption of various surface-active agents and soaps on cotton was determined under equilibrium conditions. The measurements were made by placing desized broadcloth samples in detergent solutions of various concentrations. After 24 hours of interaction in a water bath, thermostated a t 50" C., the exhaustion of the solution was determined by a titration procedure (18) suitable for all ionic types of surface-active agents. Some of the results obtained are shown in Figure 1 where the amount of each surface-active agent adsorbed was plotted against its equilibrium concentration in solution. As can be seen, a wetting agent (of the anionic type) gave the lowest adsorption values and soap the highest values. Detergent F (see Table I ) and another anionic detergent, I , both with only small amounts of inorganic salts present, gave intermediate adsorption values. Although there might exist some correlation between the equilibrium adsorption values and the effectiveness of a particular detergent, the conditions of such a test do not duplicate the practical washing process. With adequate mechanical action, equilibrium washing conditions can be reached in a few minutes.
TABLE I. DESCRIPTION O F DETERGENTS AND SUMMARY CALCIUM ADSORPTION VALUES Detergent A
B
C
D
E F
Type Built anionic Built nonionic Built soap Built anionic Nonionic Anionic
OF
Calcium Adsorption after Three Cycles, Milliequivalent/G. Cotton New cotton Used cotton 0.12 0.21 0.08 0.26 0.13 0.27 0.12 0.29 0.04 0.10 0.04 0.10
1395
I n view of the important role that the adsorption of small amounts of detergent must play in cotton detergency, the application of radioactive tracer techniques was considered. Very few published accounts were found describing the use of this new tool in the field of detergency. In a note, Hensley, Long, and Willard ( 1 1 ) described briefly their work on the reaction of radioactive ions in aqueous solutions on glass and metal surfaces. The applications of the radioactive tracer technique to metal cleaning was recently described by Harris,
P
o
I
CONCENTRATION
Figure 1.
2
3
OF S.A. AGENT
4 5 (MILLIEQUIV. / L . )
Adsorption of Surface-Active Agents on C o t t o n Equilibrium values (50° C.)
Kamp, and Yanko (10). I n this study a n organic compound was labeled with carbon-14 and was then added t o the oil used for soiling tpe test panels. Although the authors were able t o determine quantitatively minute amounts of the labeled compound remaining on the metal surfaces, they consider their results of limited significance since the compound tended to segregate from the oil and to be preferentially adsorbed on the metal surface. ADSORPTION AND 'EXCHANGE STUDIES WITH RADIOCA LCIUM
From the foregoing, one might conclude that the most suitable method for studying cotton detergency by tracer techniques would consist of labeling detergent molecules with radiocarbon or radiosulfur. Such a n approach, although of definite future interest, was'not considered for the present since the incorporation of radioisotopes in a variety of detergent molecules, if a t all possible, would have entailed a very tedious and expensive synthetic program. In the search for a tracer method more suitable in practical detergency studies, the use of radioactive bivalent ions was considered in this laboratory in 1947. Since neither calcium nor magnesium isotopes were available a t t h a t time, preliminary experiments were made with strontium which could have been labeled with strontium-89. However, it was found that the solubility of detergents which tolerate the natural hardness builders-Le., calcium and magnesium-would be much too low in water containing strontium. In 1948, when the production of radiocalcium in the nuclear reactors and its distribution through the Oak Ridge National Laboratory commenced, a suitable cation for tracer studies in the field of detergency became available. At present, calcium-45 can be obtained as calcium carbonate with varying specific activities (40) upon application to the U. S. Atomic Energy Commission. For preliminary studies in this laboratory, an irradiated unit of calcium-45 (item 13.4) was used, while the work described in the following was carried out with larger quantities of a less expensive form (item S-5B) which is a by-product in the production of carbon-14. Both samples were found to be satisfactory for the intended use. The radiation properties of calcium-45 were studied in detail by Walke, Thompson, and Holt ( 4 2 ) . The radiation was found
1396
Figure 2. -
INDUSTRIAL AND ENGINEERING CHEMISTRY
Placement of Sample Holder with Cotton Swatch into Radiation Cbunting Equipment
to consist predominantly of weak beta rays having a maximum energy of 0.25 m.e.v. The half-life of this isotope is 180 days, a sufficiently long period so that it may be used many months ' in the laboratory without excessive loss of activity. The main advantage of using radiocalcium as a tracer in detergency tests lies in the fact that it does not disturb in any way the system t o be studied. For this investigation, the calcium carbonate as obtained from Oak Ridge was dissolved in distilled water by introducing carbon dioxide through a sintered glass funnel under vigorous stirring. The concentration of all the resulting calcium bicarbonate water used in the tests was 300 p.p.m. based on calcium carbonate. The solutions of the various detergents were prepared at a uniform concentration of 2.5 grams per liter, with the exception of built soap (detergent C) which was prepared a t a concentration of 4 grams per liter in order to compensate for the precipitation of calcium soap. The wash tests were made with two types of unsoiled cotton: a new desized broadcloth and a muslin which had been in normal household use for about 6 years. [The specifications of the fabrics were as follows: English broadcloth-thread count, 144 (W) and 76 (F); weight, 3.9 ounces per square yard or 11. 2 mg. per square em. Fine muslin-thread count, over 70 (W) and 60 (F); weight, 5.0 ounces per square yard or 14.2 mg. per square em.] The latter material was treated with 1% acetic acid in order to remove the accumulated calcium and magnesium deposits following the procedure given by Heuser (14) for A.C.S. standard cellulose. The washing was carried out in 250-ml. Erlenmeyer flasks with a fabric t o liquor ratio of 1 t o 10. A minimum of four swatches was washed as a set in each c cle, wherein one swatch (5 X 3.5 inches) was sewed into a smalfbag by gathering in the edges with cotton thread. The bag was filled with glass marbles weighing a total of 20 * 1 grams. The required agitation was accomplished by placing the flasks on a modified shaking machine (-4. H. Thomas Co., model No. 8926-A) which was set for a fixed stroke of 2 inches. Strip heaters of 250-watt capacity, operated as pairs in series connection for reduced heat dissipation, were mounted on the shaking machine. It was found t h a t if the temperature of the heaters was regulated by a thermocouple-type controller a t 120" C., the over-all heat losses during shaking could be compensated and the temperature in the flasks maintained at 60 * 2' C. The conditions encountered in hard water laundering were simulated by using calcium-45-labeled bicarbonate water in the wash as well as in the rinse. Each complete cycle consisted of washing for 8 minutes in the detergent solution followed by rinsing twice for 1 minute periods. Before drying the swatches, excess liquid was removed by pressing them on a
Vol. 42, No. 7
glass plate with a 2.3-kg. roller-type squeegee. Thus a uniform moisture content of nearly 100% was obtained. The calcium uptake was measured by placing the cotton swatches in a special sample holder which exposed a definite area to the thin window of a Geiger-RIuller counter tube as shown on Figure 2. The radiation detection equipment, manufactured b Tracerlab Inc., consisted of an Autoscaler hIar% I1 (model SC-I) and a sample holder with tube mount (SC-10) with a GeigerRfuller tube (TGC-2) having a window thickness of 1.86 mg. per square em. Some aspects of radioactive tracer measurements as outlined in the pertinent literature (11,33) were considered By maintaining identical geometry and bv using swatches of uniform thickness, the c6unting rate (corrected for background and decay) is directly proportional to the amount of the labeled element (in this case calcium) on the cloth. However, if fabrics of widely different weights are being used, the relation of measured activity to sample thickness for a weak beta emitter must be taken into account (21, p. 237). Since the tn-o types of cotton cloth used in the experiments weighed well below 30 mg. per square cm., the results obtained are not strictly comparable. Nevertheless, the increase in measured activity for the muslin which was about 25% heavier still remains small (in the order of 10%) compared to the large differences between the new and used cotton, ana no corrections were made in this study.
It was intended t o carry out a series of multicycle-wash tests with the same six detergents which had been used in the studies described in the preceding paper (20). While five detergents were the identical products, detergent D used here was a newer commercial product sold under the same trade name, but not of the same composition as the one used previously. The results obtained are shown in Figures 3 and 4 and are summarized in Table I. The adsorption values reported represent averages of duplicate determinations which checked within *IO%. I n order to obtain an approximate absolute measure for the amount of calcium on the fabric, a calibration method was employed. It consisted of injecting with a micropipet 0.1 ml. of labeled solutions on spinning cloth disks (weighing 0.1 gram) which were then counted under conditions similar to those maintained during the swatch measurements. Thus, it was found that with the particular sample of calcium carbonate (item S-5B, initial specific activity: 0.26 me. per gram of calcium), 250 counts per minute corresponded t o about 0.01 milliequivalent of calcium per gram of cotton.
I e CYCLE NUMBER
3
Figure 3. Calcium Adsorption on Cotton in Multicycle Wash Tests Various detergents in 300 p.p.m. hard water
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1950
I
g
The calcium adsorption on cotton broadcloth washed for three cycles in various detergents is shown on Figure 3. It can be seen that small quantities of calcium were taken up by the cloth and accumulated to varying degrees depending on the detergent used. The unbuilt synthetic detergents E and F gave the lowest calcium adsorption values. The values obtained with radiocalcium containing water alone (not shown) practically coincided with the points shown for these detergents. I n fact, most of the measured calcium in these cases is due t o the liquid retained by the swatches before drying in each washing cycle. The detergent compositions B and A (containing E and F, respectively, with builders) gave very much higher calcium adsorption. Built soap (detergent C), probably because of some calcium soap forming on the fiber (in addition t o the normal adsorption), gave the highest value. A comparison of calcium adsorption on new and used cotton is given in Figure 4. The values obtained with the three detergents E, B, and D were plotted on a reduced scale. Although the adsorption on used cotton was found to be greatly enhanced over that on new cotton, the respective order of the three detergents was still maintained. The enhanced interaction observed with used cotton might be due partly t o chemical degradation and partly to physical changes. Referring to the latter, Heuser ( I S ) contended that the increased calcium uptake could be caused by a n increase of the amorphous portion a t the expense of the crystalline portion of the cotton fiber. It was also thought of importance to determine whether the calcium adsorption phenomena, as such, were due to a progressive deterioration of the cotton in each washing cycle. Therefore, the calcium was removed from several sets of the above swatches by the 1% acetic acid treatment described previously and, subsequently, put through further wash cycles with calcium-45labeled hard water. Only a slightly increased calcium adsorption was noted in this second series of tests. This confirms the findings of Murdison and Roberts (25) that no irreversible chemical changes take place in a few washings and i t was concluded that deterioration cannot be responsible for the observed adsorption effects. Since ion exchange has been mentioned as an important factor in detergency (23, 35), it was decided t o obtain a quantitative measure of calcium exchange in the washing process. This was accomplished by using the swatches, which had gone through three cycles with radiocalcium-labeled water, for another wash and rinse cycle with inactive hard water. The results obtained in this experiment are given in Figure 5, where the counting rate measured on the various swatches is plotted against the
1397
3
2 i
>
E
2' E 8 $
1
0 W 0:
a v)
i
I 2 3 NUMBER OF ACTIVE CYCLES WITH RADIO-CALCIUM LABELED WATER
Figure 5.
*
INACTIVE CYCLE
Cationic Exchange in Cotton Detergency
Multicyole wash tests in 300 p.p.m. hard water
wash cycles. The extent of ion exchange can be estimated by considering that another active cycle would have increased the radioactivity to still higher values. However, since the inactive cycle caused a very marked reduction in activity, it is shown t h a t a very extensive exchange of calcium takes place in each wash cycle simultaneously with its build-up on the fiber. CONCLUSIONS
The use of radiocalcium as a tracer element in detergency studies offers a convenient means for measuring some of the adsorption and exchange effects taking place during the washing process. Under the set of conditions prevailing in the above tests, the calcium adsorption values seem t o give a n indirect measure of the anionic adsorption which is closely related to the affinity of the detergent for the cotton fiber. Thus, the correlation which appears to exist between calcium up-take by the cloth and the detersive effectiveness of the bath becomes understandable. I n theoretical studies concerning the quantitative relations of ionic adsorption on cotton, the described method could furnish some of the necessary experimental data. I n particular, the Donnan membrane equilibrium theory as i t was formulated for wool 6bers (31, 38) and for the dyeing of cotton (9) should be applicable t o the cotton-detergent-calcium system. It is also believed that by developing the method further, it might become useful as a practical guide in the laboratory for formulating improved cotton detergents. ACKNOWLEDGMENT
The isotopes used were obtained on allocation from the U. S. Atomic Energy Commission. The author would like to thank W. F. Busse, formerly associate director of the laboratory, whose interest in the fundamentals of detergency has led t o this study. H e is also indebted to E. Heuser, E. Pacsu, W. P. Utermohlen, Jr., and E. I. Valko for valuable suggestions and comments. The help of Mrs. B. J. Ackerman and Miss M. Truchsess in obtaining the data and of Miss M. L. Stecker in preparing the manuscript is gratefully acknowledged.
G
2 0.2 3 w-I
i f3
*
3
0.1
s c z a
LITERATURE CITED
a
(1) Acharya, B. G. S., and Wheeler, T. S., Proc. Indian Acud. Sci.,
0
2A, 837 (1935).
I
e
3
C Y C L E NUMBER
Figure 4. Comparison of Calcium Adsorption on New and Used Cotton Multicyole wash tests in 300 p.p.m. hard water
(2) Badgley, W., Frilette, V. J., and Mark, H., IND. ENG.CHEM.,37,
227 (1945).
(3) Clegg, G. G., J. Textile Inst., 40, T449 (1949). (4) Clibbens, D. A., Ibid., 40, P426 (1949). (5) Davidson. G. F.,Ibid.. 39,T87 (1948). ( 6 ) Davidson, G. F., and Nevell, T . P., Ibid., 39, T59, T93, and
T102 (1948).
INDUSTRIAL AND ENGINEERING CHEMISTRY
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( 7 ) Frilette, V. .J., Hanle, J., and Mark. H., J . -4771. Chem. Soc., 70, 1107 (1948). ,8) Gardiner, K. W., and Smith, L. B., J . A m . 0 2 1 Chemzsts’ Soc., 26, 194 11949). _. (9) Hanson, J., Neale, S. M., and Stringfellom, IT. A4.,Trans. Paraday Soc., 31, 1718 (1935). (10) Harris, J. C., Kamp, R . E., and 1-anko, \IH., . -4STM Bull. 158, 49 (1949). ( 1 1 ) Hensley, J. W., Long, -4.O., and Willard, J. E.. J . A m . Cham. Soc., 70, 3146 (1948). (12) Hermans, P. H., “Physics and Chemkry of Cellulose Fibers,” New York, Elsevier Publishing Co., Inc., 1949. (13) Heuser, E., private communication. (14) Heuser, E., “The Chemistry of Cellulose,” S e w Tork. John Wiley & Sons, Inc., 1944. (15) Honnegger, E., and Schnyder, A , , J . TesiiZePnst., 34, T29 (1943). (16) Howsmon, J. A., Testile Research J . , 19, 152 (1949). IXD.EBG.CHEM.,40,1711 (17) Kinsinger, R’.G., and Hock, C. IT., (1948). (IS) Lambert, J. M., J . Colloid Sci., 2, 479 (1947). (19) Lambert, J. A t . , and hckerman, B. J., unpublished work (1946). (20) Lambert, J. M., and Sanders. H. L., IND. ENG.CHEY.,42, 1388 (1950). (21) Lapp, R. E., and ilndrews, H. L., “Nuclear Radiation Physics,” Sew York, Prentice-Hall. Inc., 1948. (22) Lauer, K., Kolloid Z . , 107, 86, 93 (1944). (23) McBain, J. W.,“Advances i n Colloid Science, I,” edited by Kraemer, E. O., pp. 99-142, Sen- York. Interscience P u b lishers, Inc., 1942. (24) Mark, H., J . Phys. Chem.. 44, 564 (1940). (25) Murdison, 11. E., and R o b e r t s , J. S.,J . T e z t i l e I n s t . , 40, T5O5 (lS49I. ---, (26) Xeville, H. A., and Harim >I , J . Rrsea,ch S a t l . Bui. S t a n d a r d s , 14 765 (1935). ~
\ - - - - ,
\
Vol. 42, No. 7
(27) Neville, H. 4., and Jeanson, C. A., J . Phys. Chem.,37,1001 (1933). (28) Ott, E., et al., ed., “High Polymers,” Vol. V, “Ceilulose and
Cellulose Derivatives,” New York, Interscience Publishem, Inc., 1943. (29) Paosu, E., Teztile Research J., 15, 354 (1945). 42, 545 (1946). (30) Peirce, F. T., Trans. F a r a d a y SOC., (31) Peters, L., and Speakman, J. B., J . Soc. dyer.^ Colouvists, 65, 6:3
(1949). (32) Race, E:, Ibid., 65,56 (1949). (33) Reid, A. F., “Preparation and Measurement of Isotopic Trarers,” edited by Wilson, D. TI-., et aE., pp. 83-108, Ann Arbor, J. 1%’. Edwards, 1946. (34) Rhodes, F. H., and Brainard, S. UT., IND. ENG.CHEM.,21, 60 (1929). (35) Schwartz, A. M.,and Perry, J. W ~“Surface , Active Agents,” pp. 316-84, New York, Interscience Publishers, Inc., 1949. (36) Sookne, A. hl.,and Harris, M., J . Research Natl. Bur. S t a n d n r d s , 25, 47 (1940); 26, 65, 205 (1941). (37) Spring, W., Bull. SOC. be2ge chim., 24, 17 (1910). (38) Steinhardt, J., and Harris, M., J . Research Natl. Bur. Standords. 24, 335 (1940). (39) Tjutjunnikow, B., and Pleschkowa, S., Allam. Oel- u. Fett.Ztg., 31, 59 (1934). (40) U. S. Atomic Energy Commission, Isotopes Division, Oak Ridge, Catalogue and Price List No. 3, 1949. (41) Valko, E., “Kolloidchemische Grundlagen der Textilveredlung,” Berlin, Julius Springer, 1937. (42) Walke, H., Thompson, F. C., and Halt, J.. Phys. Rec., 57, 177
(1940). (43) Ward, K., Jr., Am. DyestuflRrptr.. 38, 122 (1949). RECEIVED Soveinber 21, 1949. Presented before the Division of Colloid Chemistry a t the 110th Meeting of t h e AMERICAN CHEXICALSOCIETY. Atlantic City, h-.J.
Thermal Transfo ations of Aluminas and Alumina Hydrates J
H. C. STU31PF. ALLEN S. RUSSELL, J . W. NEWSO>IE, AND C. 31. TUCKER Aluminum Company of .4nieric*u, Vetr liensington, P a .
T h e phase transformations occurring in the thermal decomposition of the four alumina hydrates have been examined by x-ray powder diffraction analysis. A series of distinct patterns has been identified in the region which previously has been designated loosely as y-alumina. The seven crystalline modifications of the nearly anhydrous aluminas from heating pure alumina hydrates are arbitrarily designated as a-, 7-,6-, 7-, e-, K - , and X-alumina.
7-4lumina has a cubic, spinel-type structure; y-, 6-, e-, and K-aluminas are not cubic. The transformation sequences and temperatures are shown for various samples of the hydrates heated both in dr) air and in steam. 411 interesting feature of these tranbformations is that a-alumina monohydrate J ields differing phases on dehj dration when formed by direct precipitation, by dehydration of a-trihydrate, or by dehydration of p-trihydrate.
T
in t,he late trventies ( 1 ) . T h r hydrate which is produced by weding and autoprecipitation in the Bayer process is termed a-alumina trihydrate; it gives the same x-ray pat,tern as t h e mineral gibbsite. Another trihydrate produced by rapid precipitation from sodium aluminate solution is termed p-alumina trihydratr; it has been called bayerite by German writers, although it is not a product of the Bayer process. There are also two monohydrates. The one commonly occurring in certain types of bauxite ore is termed a-alumina monohydrate, and has also been given the name of boehmite. The second form is termed p-alumina monohydrate and corresponds t o the mineral diaspore. In the case of the aluminas the terminology does not follow any regular pattern, inasmuch as the several forms were not discovered in any logical order and the names p- and (-alumina have been adopted for aluminas containing sodium and lithium.
HERMAI, decomposition of the various alumina hydrates yields a number of crystalline variations of alumina which are transition stages in a process eventually yielding corundum: The sequences of these transformations have been fairly well known a t these laboratories for a number of years, but recently a new investigation was conducted t o verify these and t o make certain that the forms of alumina which were recognized were distinct. This paper presents the results of some of the x-ray powder diffraction studies, illustrating the changes in crystalline form which occur when the hydrates are heated at temperatures up t o 1200” C. Weight losses and surface areas as determined by hutane sorption for these same specimens are reported by Russell and Cochran ( 5 ) . The terminology used in referring t o the alumina hydrates is essentially that adopted by Aluminum Research Laboratories
-
