LETTERS Water-What's
Really Peculiar?
To The Editor: Each month I read with interest the various features in the Journal of Chemical Education and commonlv find manv intriguing and innovativeideas which are useful in my college teaching. However, on occasion I encounter statements which at best are misleading and, at worst, incorrect. There was one such instance in "Thumbnail Sketches" in the December 1980 JOURNAL. In the article "Water, the Peculiar Mo1ecule"Dr. Orna makes the statement ". . .the properties of water deviate markedly from those of its periodic analogs CH4, NHBand HF". I would like to point out that the periodic analogs of water are HdS. - ,HnSe..and H?Te not CH.... NH?. ". and HF. Furthermore, NH3 and HF differ from their proper periodic analoes IPHQ.ASH*.ShH-. and HC1. HBr. HF. res~ectivelv)in theusame manner as w>er differs from H&, etc. Not & l y water. hut also HF and NH!I differ from their periodic analogs in ha;ing abnormally highmelting points and high heats of vaporization. These abnormalities result from intermolecular H-bonding. In fact, H F forms stronger H-bonds than does water.
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ternary phase diaaam has a negative slope, resultingfrom the fact that the solid has a lower densitv than the liauid. which in turn arises from the fact that the number or un'shared electron pairs and the number of H-atoms in the Hz0 molecule are equal, leading to theveryMopen"tetrahedral structure in ice. In most other respects, water is qualitatively similar in its periodic table relationships to NHn and HF, and in these respects is not highly peculiar.
James M. Garrett Bruce A. Henry Charles R. Cates Stephen F. Austin State University Nacogdaches,T X 75962
Copper in Apple Ash Glazes lor Ceramics: An Example of Environmental Chemistry and Chemistry for Potters
To the Editor: We read the article by Denio on "Chemistry for Potters" [J. CHEM.EDUC.,57, 272 (1980)] with interest, particularly his discussion of the redox chemistry of copper in glazes. Several years ago we were experimenting with copper-containing glazes and reduction firing to obtain the red color associated with presence of Cn(1). At the same time we were also making glazes from wood ash and were surprised to find that
Harrv H. Sisler University of Florida Gainesville. FL 32611
Lagormorpha Enantiomorphs-Simple
Stereomodels
To the Editor: The recent report of Niac and Florea on their observation of natural VSEPR walnut models' prompts us to report our observation of stereoisomers in the rabbit hutch. The two domestic bunnies shown, aptly named Dextro and Levo, were horn each with one flop ear. The fact that the distorted ears were on opposite sides of their heads immediately made the two non-superimposahle mirror images. In the litter these two were unique; their siblings were prochiral at best. A collea~uesueaested that perhaps if viewed, through a polaroid lens, rot&g the lensto the right would causeone of the two to disappear and rotating the lens to the left would cause the other to vanish. Unfortunately before this theory could he resolved, the two were converted to racemic rabbit stew.
' N i x , G. and Florea, D., J. CHEM.EDUC.,51,429 [1980].
448
Journal of Chemical Education
contained conoer. The ash ha2 resulted from destruction of an old orchard that had not been used for approximately 20 years, hut which had been treated regularly with a copper containing spray prior to that time. Analysis of the ash (acid digestion, flame atomic absorption, deuterium background correction) revealed 0.17%copper (dry weight), certainly sufficient to cause the characteristic red color i f a reduced copper glaze. Other ash glazes in our studio have not given the red color and have negligible copper content, e.g. bracken ash (
