P. A. Christian and 1. H. Berkal
Worcester Polytechn~cInstitute Worcester, Massachusetts 01609
Polywater:
and Opportunity in Science
The current "What is Polywater?" controversy ( 1 , Z) provides a striking illustration for students regarding the distinction between carefully conducted experimental studies and theoretical rationalization of the experimental facts. Regardless of which answer to the polywater question will eventually be generally accepted as "correct," the "final" explanation must be consistent (or a t least not inconsistent) with new observations that students may make in pursuing studies of polywater and other anomalous residues. Allen (3) has pointed out that "It [anomalous water] almost seems like a model for the ideal research topic that one always tells one's bright young students to be looking for." The response obtained from college students at a recent symposium (4) and from high school students elsewhere on hearing about the results of our recent studies (5, 6) indicates the interest in anomalous liquids which has been generated in students. With the hope of stimulating further student interest, we present an intriguing observation that we have made, as well as offer outlines of some possible studies that can be undertaken in any adequately equipped high chemistry . -- school or college laboratory. The figure shows photomicrographs of a typical sample of polywater and a rather unusual sample, which we grew (6). In the typical sample the polywater column is the white segment in the middle of the dark horizontal strip (the bore of the capillary). Similar photographs have been obtained by others (7, 8). The other sample, however, consists of a set of more or less equally spaced narrow bands perpendicular to the bore direction. This "stepladder" effect was observed in several samples from different ~
A Lesson
polywater preparations. Since our columns were grown in an unevacuated dessicator, perhaps this phenomenon may be explained by the entrapment of air during column growth. Thus far, the following liquids have produced anomalous columns: water, methanol, ethanol, propanol, acetic acid, acetone, benzene, toluene, and carbon tetrachloride (6, 6, 9, 10). Many other liquids can be investigated. The major requirements for these liquids are that they have a reasonably high vapor pressure at room temperature and that they are obtainable in a relatively pure form. Examples are (CHa)2SO, CSa, and CsHit. The preparation of anomalous columns starting with mixtures of two normal liquids may produce interesting visual effects, such as the one mentioned above, in the resulting residues. The vapor phase must contain comparable partial pressures of the two components. Immiscible liquids must be emulsified or separated in such a way as to provide contact of the vapor phase with both liquid components; otherwise the vapor phase will consist primarily of the less dense component. Properties of anomalous residues can be determined by unique "under the microscope" experiments. Drops of a normal liquid are placed a t the ends of a capillary containing a residue; the vapor of the normal liquid diffuses in and condenses on the residue. I n some cases we have observed mixing to occur to give a homogeneous phase and in other cases the residue and normal liquid appear to be immiscible. Such "soluTo whom wrrespondenccshould be addressed.
Volume 48, Number 10, October 1971 / 667
bility" studies using a variety of solvents and/or anomalous residues are of interest. Morariu and co-workers (11) report that they have treated polywater with wncentrated hydrofluoric acid and find little evidence of reaction. Perhaps the reader can imagine chemical reactions that could he attempted. A whole new field of truly micro-micro chemistry has been opened up to students in which, with a little imagination, they can pioneer. Thus, unlike those who conclude that "American scientists have been wasting their time studying this subject" ( I @ , we feel that the lessons which students can learn may well prove to be worth the time. Liiemiure Ciied (1) Dmr*onr, B.V., Sci. A m r . , 223 (51,52 (1970). (2) Ronaarno, D. L., AND PORTO, 8. P . S.,SC(~(ICB, 167. 1715 (1870). (3) ALLEN.L. 6..Scienca. 169.718 (1970). (4) C ~ ~ r a ~ x nP l. * .A., AND B m m . L. H.. ''Prenaretion of Columns of Anomalous Lhuida." p p e r delivered at the Undergradvata Reswrch S3mposium. SUNY A l h y , November 14.1970. (5) C ~ z m s ~ r A x r. , A.. AND BmRr*, L. H.. ChodaUy. 44 (I),25 (1971). ~ ,A.. A N D B m m , L. H., Chem. Commw., 487 (1871). (8) C ~ a t e T x aP. G. I. --~ --.-, J., Osnom. A. R.. LIPPINCOTP. E. R., AND
BANDY, A. R., Charn.Ind.. 688 (May 24. 1968). (8) DERYAOIN, U. V., AND FEDYAPTN,N. N.. DokL Ahad. N& SSSR, 147,403 (1982). (10) Dsnu&am, B. V.. P n n u ~ a N. ~ ~N., . AND T A U ~ YM , . v., J . cdbid Inlerfmc Soi., 24, 132 (1967). (11) MORARID, V. V., I\IILLB. R., ANY !VOO~P,L. A,, Noturn, 227, 373 (1970). (12) Davrs, R.E..Cham.En& Nclua. 73 (Sept.28.1870).
(8) Be==nuu. L.
Polyxater columns. A, Typical somple; B, unurvol sample ImoanoRca lion is 200X in each case).
668
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Journal of Chemical Educafion
