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A kinetic argument against the existence of anomalous water
A Kinetic Argument Against the Existence of Anomalous Water E L L I S O N H. T A Y L O R Chemistry Division, Oah Ridge National Laboratory 1, Oak Ridge, Tennesgee 87880
Received July 20, 1970; accepted September 8, 1970 Anomalous water is commonly supposed to be produced by a catalytic process, and the cessation of growth after a time is attributed to poisoning. An examination of the poisoning according to generally accepted ideas in catalysis indicates that the concentrations which would result would be far smaller than are claimed. This discrepancy can easily be resolved by attributing the phenomena to condensation of water on soluble impurities. Considerable evidence has accumulated that so-called anomalous water is not a new liquid form of water but, in reality, a solution of impurities (i, 2). Samples prepared according to recipes for making anomalous water showed infrared spectra similar to those reported for supposedly genuine "polywater", and these samples were shown to be loaded with impurities. However, these spectra (and others obtained in attempts to match the polywater spectra b y purposeful addition of impurities (2, 3)) do not agree perfectly with the originals. Furthermore, the impurities reported differ rather widely (1, 2, 4). Both of these imperfections in the experimental ease against anomalous water are understandable and do not seem telling to an ab initio sceptic, but they leave a smaI1 residue of dissatisfaction with the outcome. For that reason, it seems desirable to look into more general objections to the existence of this material. One of the most striking features of anomalous water has been the inability to produce it in more than minute amounts. Columns of material appear randomly in capillaries, increase slowly in length, and then cease to grow. This is to be expected for condensation of ordinary water on soluble impurities but requires explanation if the process is the production of a polymer b y
1 I~esearch sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corp.
catalysis. The standard explanation, and the only one available, is that the catalyst is somehow poisoned. However, a more detailed examination of this explanation leads to contradiction with other observations. To demonstrate this contradiction, we assume the existence of anomalous water as a polymer, ~ highly stable relative to liquid water (5, 6). Under this assumption, the only feasible poison is the polymer itself. Liquid water could not be, because a catalyst capable of overcoming the large activation energy must interact too strongly with water molecules for the interaction to be seriously perturbed by the intermolecular binding in ordinary liquid water. A high activation energy is required to prevent spontaneous conversion in nature or in the laboratory. The poison cannot be an extraneous one in the atmosphere or growth chamber, since the capillaries are in contact with those before growth begins. The poisoning might arise from a rearrangement of a catalytically active site through dissolution by the polymer, but this should be operative as soon as the polymer is formed (at monolayer coverage). Also, a given capillary should not catalyze a second growth of material a after eva~Not necessarily a high polymer. Derjaguin (7) reports a molecular weight around 200. 3 I have frequently observed a second growth on the site of a column removed by evacuation. Derjaguin reports the same behavior on a fiat plate (8). Journal of Colloid and Interface Science, Vol. 36, No. 4, August 1971
543
544
TAYLOR
poration of the condensate if this mechanism were operative. One could also postulate poisoning by a soluble material being adsorbed on active centers. The soluble material could not be the glass itself since the transmigrated atoms would likewise not permit a second growth in the same capillary. Poisoning by ~n extraneous soluble material would demand a coincidence which would be most unlikely to occur with such regularity, namely, the simultaneous presence at the site of each column of active catalytic centers and of an appropriate soluble impurity to serve as a poison. Also, only a volatile impurity would permit a second growth in the same capillary. The hypothetical polymer is well ~dapted to being a poison, since there should be a rather strong interaction between each H20 unit and the ordinary silica surface in addition to the necessarily very strong interactions at the catalytic sites. We wish to estimate the amount of polymer that could be formed before poisoning is complete, which must be at or before the achievement of a monolayer. We assume a polymer with dimensions like those suggested by Lippincott et al. (6)z Each H20 unit would then require about 5A2 of surface, and 1 cm of capillary length would accommodate (n~D/5) N 1012 H20 units, where n is the number of sheets of closely bonded I-I20 units in the polymer molecule and D is the capillary diameter in microns. When (nv:D/5) X 1012 H20 units of polymer have accumulated per centimeter of tube length, the catalytic activity of the glass surface should be completely poisoned, and no further growth of polymer should occur. The polymer is, of course, compatible with ordinary liquid water, ~ and the latter would condense on it until stopped by equalization of water partial pressures in the supply and from the solution. The amount of ordinary water thus condensed would be that contained in the volume of the capillary (less the negligible volume of the monolayer) or (~D~ X 10-8/4) X 6 X 102~/18 = ~D 2 X 1015/12 water units per centimeter 4 N o t e d i n m ~ n y r e p o r t s , p a l ' t i c u l ~ r l y in r e f e r e n c e 9, w h e r e p r e p a r a t i o n of ~ h o m o g e n e o u s s o l u t i o n of p o l y w a t e r i n w ~ t e r is d e s c r i b e d .
of length. Then the weight fraction of polymer would be
mrD X 1012/5 ~ 3 X 10-3n ~D2 X 1015/12-
D
It seems unlikely that n could be as big as 10. A cube of this dimension would have a molecular weight of 18,000, far exceeding any estimates that have been made. Let us, however, set n = 10 and take D = 30 microns, a typical size. Then the maximum weight fraction of polymer we could expect would be 3 X 10 N 10-3/30 = 10-~. This is in serious contradiction with most estimates of the concentrations obtainable, as shown in Table I. The estimates of the fraction of polymer are those of the authors except for that obtained from vapor pressure lowering. Here, Raoult's law is assumed to hold when expressed in volume fraction. This is probably not seriously wrong for so dilute a solution, even of a polymer (12). Although recent publications and discussions on anomalous water describe the use of evaporation to concentrate the as-grown material, this was not indicated in any of the cases cited in Table I. The contradiction between the values in Table I and the maximum deduced from simple considerations of poisoning is obvious. To resolve it one has the choice of rejecting the measurements of Table I, abandoning the well-established simple picture of catalytic poisoning, or denying the existence of a new-, stable form of liquid water. One cannot allow the new water to be met~stable with respect to the normal liquid since this would require it to be even more unstable with respect to the unsaturated vapor from which it is supposed to grow spontaneously. Rejecting the measurements of Table I is tantamount to rejecting the existence of anomalous water, since they include most of the types of measurement from which its existence is inferred, colligative properties, phase separation, and spectroscopy. One is then left with a choice between abandoning a simple argument based on standard ideas from kinetics or giving up the existence of anomalous water. If an alternative explanation for the various observations is avail-
Journal of Colloid and Interface Science, Vol. 36, No. 4, August 1971
EXISTENCE
OF
ANOMALOUS
TABLE I CONCENTRATIONS OF POLYMER CLAIMED IN VARIOUS PREPARATIONS OF ANOMALOUS
WATER Propelty by which concn was assessed
Vapor pressure Refractive index Vohme change Molecular spectra
Wt. fraction of polymer
Reference
0.07 0.2 to 1.0 0.02 to 0.6 Almost no H20
10 11 7 6
able, then it is obviously preferable to give up the existence of anomalous water. There is such an explanation, namely, that the material observed is formed by condensation of water vapor on random portions of soluble impurity. These may be, in different eases, dust particles, residues of cleaning agents trapped in some flaw, or inclusions from the glass-making process. Because the condensation usually occurs in fine capillaries, only minute amounts of impurity are necessary to give relatively concentrated solutions. Thus a 21-micron cube of NaC1 would give a 0.1-mm length of 10 wt % solution in a 50-micron diameter capillary. Such a particle would probably not be noticed in the original large tube, and the process of drawing the capillary would probably spread the particle over the capillary in a film too thin to be apparent. Since the distinction between surface and interior of the glass is probably maintained during drawing, it is not obvious how impurities that were beneath the surface in the original tube could become accessible to the surface in the resulting capillary. If the original surface was adequately cleaned of soluble particles or inclusions one would thus expect the capillary to be similarly clean. However, a particulate inclusion would probably have much greater viscosity than the glass at the working temperature and might therefore move erratically under the stresses of drawing. Further, an inclusion of a solution (from cleaning) communicating only through some microscopic hole or fissure with the surface might well blow out to the surface during drawing as a result of the pressure that would be developed. Condensation on a soluble, loealized impurity obviously explains the observed kinet-
WATER
545
ics of formation (13) including its cessation, and also the random and infrequent successes in attempting to grow the material. The admission of different origins of impurities can explain the differences in composition that have been reported (1, 2, 4). Derjaguin recognized the possibility of a soluble impurity at an early stage (10), but considered only a homogeneously distributed impurity (either the glass itself or an impurity in it), and concluded that the solubility of silica glass was too low and the diffusion of impurities in it too slow to explain Fedyakin's observations (14). The possibility of explaining the spectroscopic observations on the basis of a solution rather than a new form of water has been suggested (1, 2). Rather diverse solutes have been observed or postulated in different cases, but a particulate origin seems applicable to all of them. It has been suggested (1, 2) that the solute reaches the capillary by creep from the reservoir, the solute either being added to the water as a vapor pressure depressant or being picked up from the surface during creeping. Some experiments support this view rather directly (2), but it is hard to understand what driving force exists for gross, continuing creep in a closed system where there is no net loss of solvent by evaporation. It is clear in a qualitative way that Derjaguin's various physical chemical observations can be explained as representing the properties of a solution. More detailed explanations have been given (15) and will be reported in a more extensive paper by Bredig and the author. Therefore, since the hypothesis of condensation of water on random impurities appears to be a satisfactory alternative to that of the existence of a new form of water, it seems preferable by far to abandon the latter rather than to give up the standard kinetic ideas which are the basis of the argument presented here. REFERENCES 1. ROUSSEAU,D. L., AXDPORTO,S. P. S., Scienc~ 167, 1715 (1970). 2. ~.ABIDEAU, S. W., AND FLORIN, A. E., S c i e n c e
169, 48 (1970).
3. BREDIa, M. A., Personal communication. Journal of Colloid and Interface Science, Voh 36, No. 4, August 1971
546
TAYLOR
4. BASCOM,W. D., BROO~:S,E. J., ANDWORTHIING9. PAGE, JR., T. F., JAKOBSEN, R. J., AND LIPTON, III, B. N., Naval Research Laboratory PINCOTT, E. R., Science 167, 51 (1970). 10. DERJAGUIN, B. V., TALAEV, M. V., AND Report, NRL-7115-1 (1970). 5. DERJAGUIN, B. V., CHtURAEV, N. V., FEDYAFEDYAI(IN, N . N . , Dokl. A/cad. Nauk SSSR 165,597 (1965). KIN, N. N., TALAEV, M. V., AND ERSI-IOVA, 11. CASTELLION,G. A., GRABAR, D. G., HESSION, I. G., Izv. Akad. Nauk SSSR, Ser. Khim. 10, J., ANn BURKHARD, H., Science 167, 865 2178 (1967). (1970). 6. LIPPINCOTT,E. R., STROMBERG,R. R., GRANT, W. I~., AND CESSAC, G. L., Science 164, 1482 12. HILDEBRAND, J. H., AND SCOTT, R. L., "The Solubility of Nonelectro]ytes," p 353. Rein(1969). hold, New York, 1950. 7. ])ERJAGUIN, B. V., ZHELEZNYI, B. V., ZAK~ HAVAEVA, N. N., KISELEVA, O. A., KONO- 13. DERJAGUIN,B. V., ERSHOVA, I. G., SIMONOVA, V. ]~H., AND CYIURAEV, N. V., Teor. Eksp. VALOV, A. I., LYCtINIKOV, ]). S., RABINOKhim. 4, 528 (1968). VICI.I,YA. I., TALAEV,M. V., AND CHtURAEV, 14. FEDYAKIN, N. N., Kolloid. Zh. 24, 497 (1962). N. V., Dokl. Akad. Nauk SSSR 189, 1282 15. TAYLOR, E. H., Oak Ridge National Labora(1969). tory, Chemistry Division Annum Progress 8. ]--)ERJAGUIN,B. V., ZORIN, Z. M., ANDCHURAEV, Report for period ending May 20, 1970, N. V., KoUoid. Zh. 30, 308 (1968). ORNL-4581.
Journal of Colloid and Interlace Science, Vol 36, No. 4, August 1971
Received July 20, 1970; accepted September 8, 1970 Anomalous water is commonly supposed to be produced by a catalytic process, and the cessation of growth after a time is attributed to poisoning. An examination of the poisoning according to generally accepted ideas in catalysis indicates that the concentrations which would result would be far smaller than are claimed. This discrepancy can easily be resolved by attributing the phenomena to condensation of water on soluble impurities. Considerable evidence has accumulated that so-called anomalous water is not a new liquid form of water but, in reality, a solution of impurities (i, 2). Samples prepared according to recipes for making anomalous water showed infrared spectra similar to those reported for supposedly genuine "polywater", and these samples were shown to be loaded with impurities. However, these spectra (and others obtained in attempts to match the polywater spectra b y purposeful addition of impurities (2, 3)) do not agree perfectly with the originals. Furthermore, the impurities reported differ rather widely (1, 2, 4). Both of these imperfections in the experimental ease against anomalous water are understandable and do not seem telling to an ab initio sceptic, but they leave a smaI1 residue of dissatisfaction with the outcome. For that reason, it seems desirable to look into more general objections to the existence of this material. One of the most striking features of anomalous water has been the inability to produce it in more than minute amounts. Columns of material appear randomly in capillaries, increase slowly in length, and then cease to grow. This is to be expected for condensation of ordinary water on soluble impurities but requires explanation if the process is the production of a polymer b y
1 I~esearch sponsored by the U. S. Atomic Energy Commission under contract with the Union Carbide Corp.
catalysis. The standard explanation, and the only one available, is that the catalyst is somehow poisoned. However, a more detailed examination of this explanation leads to contradiction with other observations. To demonstrate this contradiction, we assume the existence of anomalous water as a polymer, ~ highly stable relative to liquid water (5, 6). Under this assumption, the only feasible poison is the polymer itself. Liquid water could not be, because a catalyst capable of overcoming the large activation energy must interact too strongly with water molecules for the interaction to be seriously perturbed by the intermolecular binding in ordinary liquid water. A high activation energy is required to prevent spontaneous conversion in nature or in the laboratory. The poison cannot be an extraneous one in the atmosphere or growth chamber, since the capillaries are in contact with those before growth begins. The poisoning might arise from a rearrangement of a catalytically active site through dissolution by the polymer, but this should be operative as soon as the polymer is formed (at monolayer coverage). Also, a given capillary should not catalyze a second growth of material a after eva~Not necessarily a high polymer. Derjaguin (7) reports a molecular weight around 200. 3 I have frequently observed a second growth on the site of a column removed by evacuation. Derjaguin reports the same behavior on a fiat plate (8). Journal of Colloid and Interface Science, Vol. 36, No. 4, August 1971
543
544
TAYLOR
poration of the condensate if this mechanism were operative. One could also postulate poisoning by a soluble material being adsorbed on active centers. The soluble material could not be the glass itself since the transmigrated atoms would likewise not permit a second growth in the same capillary. Poisoning by ~n extraneous soluble material would demand a coincidence which would be most unlikely to occur with such regularity, namely, the simultaneous presence at the site of each column of active catalytic centers and of an appropriate soluble impurity to serve as a poison. Also, only a volatile impurity would permit a second growth in the same capillary. The hypothetical polymer is well ~dapted to being a poison, since there should be a rather strong interaction between each H20 unit and the ordinary silica surface in addition to the necessarily very strong interactions at the catalytic sites. We wish to estimate the amount of polymer that could be formed before poisoning is complete, which must be at or before the achievement of a monolayer. We assume a polymer with dimensions like those suggested by Lippincott et al. (6)z Each H20 unit would then require about 5A2 of surface, and 1 cm of capillary length would accommodate (n~D/5) N 1012 H20 units, where n is the number of sheets of closely bonded I-I20 units in the polymer molecule and D is the capillary diameter in microns. When (nv:D/5) X 1012 H20 units of polymer have accumulated per centimeter of tube length, the catalytic activity of the glass surface should be completely poisoned, and no further growth of polymer should occur. The polymer is, of course, compatible with ordinary liquid water, ~ and the latter would condense on it until stopped by equalization of water partial pressures in the supply and from the solution. The amount of ordinary water thus condensed would be that contained in the volume of the capillary (less the negligible volume of the monolayer) or (~D~ X 10-8/4) X 6 X 102~/18 = ~D 2 X 1015/12 water units per centimeter 4 N o t e d i n m ~ n y r e p o r t s , p a l ' t i c u l ~ r l y in r e f e r e n c e 9, w h e r e p r e p a r a t i o n of ~ h o m o g e n e o u s s o l u t i o n of p o l y w a t e r i n w ~ t e r is d e s c r i b e d .
of length. Then the weight fraction of polymer would be
mrD X 1012/5 ~ 3 X 10-3n ~D2 X 1015/12-
D
It seems unlikely that n could be as big as 10. A cube of this dimension would have a molecular weight of 18,000, far exceeding any estimates that have been made. Let us, however, set n = 10 and take D = 30 microns, a typical size. Then the maximum weight fraction of polymer we could expect would be 3 X 10 N 10-3/30 = 10-~. This is in serious contradiction with most estimates of the concentrations obtainable, as shown in Table I. The estimates of the fraction of polymer are those of the authors except for that obtained from vapor pressure lowering. Here, Raoult's law is assumed to hold when expressed in volume fraction. This is probably not seriously wrong for so dilute a solution, even of a polymer (12). Although recent publications and discussions on anomalous water describe the use of evaporation to concentrate the as-grown material, this was not indicated in any of the cases cited in Table I. The contradiction between the values in Table I and the maximum deduced from simple considerations of poisoning is obvious. To resolve it one has the choice of rejecting the measurements of Table I, abandoning the well-established simple picture of catalytic poisoning, or denying the existence of a new-, stable form of liquid water. One cannot allow the new water to be met~stable with respect to the normal liquid since this would require it to be even more unstable with respect to the unsaturated vapor from which it is supposed to grow spontaneously. Rejecting the measurements of Table I is tantamount to rejecting the existence of anomalous water, since they include most of the types of measurement from which its existence is inferred, colligative properties, phase separation, and spectroscopy. One is then left with a choice between abandoning a simple argument based on standard ideas from kinetics or giving up the existence of anomalous water. If an alternative explanation for the various observations is avail-
Journal of Colloid and Interface Science, Vol. 36, No. 4, August 1971
EXISTENCE
OF
ANOMALOUS
TABLE I CONCENTRATIONS OF POLYMER CLAIMED IN VARIOUS PREPARATIONS OF ANOMALOUS
WATER Propelty by which concn was assessed
Vapor pressure Refractive index Vohme change Molecular spectra
Wt. fraction of polymer
Reference
0.07 0.2 to 1.0 0.02 to 0.6 Almost no H20
10 11 7 6
able, then it is obviously preferable to give up the existence of anomalous water. There is such an explanation, namely, that the material observed is formed by condensation of water vapor on random portions of soluble impurity. These may be, in different eases, dust particles, residues of cleaning agents trapped in some flaw, or inclusions from the glass-making process. Because the condensation usually occurs in fine capillaries, only minute amounts of impurity are necessary to give relatively concentrated solutions. Thus a 21-micron cube of NaC1 would give a 0.1-mm length of 10 wt % solution in a 50-micron diameter capillary. Such a particle would probably not be noticed in the original large tube, and the process of drawing the capillary would probably spread the particle over the capillary in a film too thin to be apparent. Since the distinction between surface and interior of the glass is probably maintained during drawing, it is not obvious how impurities that were beneath the surface in the original tube could become accessible to the surface in the resulting capillary. If the original surface was adequately cleaned of soluble particles or inclusions one would thus expect the capillary to be similarly clean. However, a particulate inclusion would probably have much greater viscosity than the glass at the working temperature and might therefore move erratically under the stresses of drawing. Further, an inclusion of a solution (from cleaning) communicating only through some microscopic hole or fissure with the surface might well blow out to the surface during drawing as a result of the pressure that would be developed. Condensation on a soluble, loealized impurity obviously explains the observed kinet-
WATER
545
ics of formation (13) including its cessation, and also the random and infrequent successes in attempting to grow the material. The admission of different origins of impurities can explain the differences in composition that have been reported (1, 2, 4). Derjaguin recognized the possibility of a soluble impurity at an early stage (10), but considered only a homogeneously distributed impurity (either the glass itself or an impurity in it), and concluded that the solubility of silica glass was too low and the diffusion of impurities in it too slow to explain Fedyakin's observations (14). The possibility of explaining the spectroscopic observations on the basis of a solution rather than a new form of water has been suggested (1, 2). Rather diverse solutes have been observed or postulated in different cases, but a particulate origin seems applicable to all of them. It has been suggested (1, 2) that the solute reaches the capillary by creep from the reservoir, the solute either being added to the water as a vapor pressure depressant or being picked up from the surface during creeping. Some experiments support this view rather directly (2), but it is hard to understand what driving force exists for gross, continuing creep in a closed system where there is no net loss of solvent by evaporation. It is clear in a qualitative way that Derjaguin's various physical chemical observations can be explained as representing the properties of a solution. More detailed explanations have been given (15) and will be reported in a more extensive paper by Bredig and the author. Therefore, since the hypothesis of condensation of water on random impurities appears to be a satisfactory alternative to that of the existence of a new form of water, it seems preferable by far to abandon the latter rather than to give up the standard kinetic ideas which are the basis of the argument presented here. REFERENCES 1. ROUSSEAU,D. L., AXDPORTO,S. P. S., Scienc~ 167, 1715 (1970). 2. ~.ABIDEAU, S. W., AND FLORIN, A. E., S c i e n c e
169, 48 (1970).
3. BREDIa, M. A., Personal communication. Journal of Colloid and Interface Science, Voh 36, No. 4, August 1971
546
TAYLOR
4. BASCOM,W. D., BROO~:S,E. J., ANDWORTHIING9. PAGE, JR., T. F., JAKOBSEN, R. J., AND LIPTON, III, B. N., Naval Research Laboratory PINCOTT, E. R., Science 167, 51 (1970). 10. DERJAGUIN, B. V., TALAEV, M. V., AND Report, NRL-7115-1 (1970). 5. DERJAGUIN, B. V., CHtURAEV, N. V., FEDYAFEDYAI(IN, N . N . , Dokl. A/cad. Nauk SSSR 165,597 (1965). KIN, N. N., TALAEV, M. V., AND ERSI-IOVA, 11. CASTELLION,G. A., GRABAR, D. G., HESSION, I. G., Izv. Akad. Nauk SSSR, Ser. Khim. 10, J., ANn BURKHARD, H., Science 167, 865 2178 (1967). (1970). 6. LIPPINCOTT,E. R., STROMBERG,R. R., GRANT, W. I~., AND CESSAC, G. L., Science 164, 1482 12. HILDEBRAND, J. H., AND SCOTT, R. L., "The Solubility of Nonelectro]ytes," p 353. Rein(1969). hold, New York, 1950. 7. ])ERJAGUIN, B. V., ZHELEZNYI, B. V., ZAK~ HAVAEVA, N. N., KISELEVA, O. A., KONO- 13. DERJAGUIN,B. V., ERSHOVA, I. G., SIMONOVA, V. ]~H., AND CYIURAEV, N. V., Teor. Eksp. VALOV, A. I., LYCtINIKOV, ]). S., RABINOKhim. 4, 528 (1968). VICI.I,YA. I., TALAEV,M. V., AND CHtURAEV, 14. FEDYAKIN, N. N., Kolloid. Zh. 24, 497 (1962). N. V., Dokl. Akad. Nauk SSSR 189, 1282 15. TAYLOR, E. H., Oak Ridge National Labora(1969). tory, Chemistry Division Annum Progress 8. ]--)ERJAGUIN,B. V., ZORIN, Z. M., ANDCHURAEV, Report for period ending May 20, 1970, N. V., KoUoid. Zh. 30, 308 (1968). ORNL-4581.
Journal of Colloid and Interlace Science, Vol 36, No. 4, August 1971