Langmuir 1991, 7, 2869
2869
Comments Perpetuum Mobile? In a recent letter to Nature, "No capillary rise?", G. M. Graham' reports experiments in which water in capillary tubes closed at the bottom move slowly upward by condensation or downward by evaporation to a level almost that of a surrounding reservoir; whereas in capillary tubes open at the bottom, water rises quickly to the level predicted by the Laplace equation,2 h = 2a/pgr. This experimental result contradicts the theoretical prediction of K e l ~ i n . ~ The difference in behavior between open and closed bottom tubes suggests the possibility that, with the aid of an appropriate demon to open a water-tight valve when the water level is at its lowest and close it when the level is at its highest, the ascending water could be made to do useful work. The work would be equal to 2ra2/pg which
for water is 3 X 104 J. The demon assigned to open and close the valve need not be aa discriminating as maxwell'^.^ He merely needs to open and close the valve at suitable intervals, about every 2 years. While the power provided by the rise of water in a single capillary is small and a complete cycle long, a reasonably sized body of water is sufficient to hold enough capillaries (2 X 109 to keep a 100-W bulb lit perpetually. Ian D.Morrison Webster Research Center, Xerox Corporation Webster, New York, 14580 Received May 22,1991 In Final Form: July 26, 1991
(1) Graham, G. M. Nature 1991,350, 198. (2) de Laplace, P. S. Mechanique Celeste, Supplement to Book 10,
1806. (3) Thomeon, W. A.oc. R. SOC.Edinburgh 1869-70, 63-68.
(4) Maxwell, J. C. Theory of Heat; Appleton: New York, 1872; p 308 (reprinted by A M s New York, 1972).
Additions and Corrections Oligoimide Monolayers Covalently Attached to Gold Wing Sum V. Kwan, Ljiljana Atanasoska, and Larry L. Miller' Langmuir 1991, 7, 1419-1425 The figure on the cover of issue 7, 1991, is incorrect because the wrong end of the molecules is attached to gold. See Figure 4 on page 1425 for a correct representation.
0743-7463f 91f 2407-2869$02.50/0 0 1991 American Chemical Society
