Dorothy Wrinch and the Structure of Protelns To The Editor:
The article by Maureen Julian [1984, 61, 8901 helongs to the eenre of women nromotine the careers of other women. as &e goalmay he for finding role overdue and models for career women. others should not emulate "Dorothy Wrinch and a ~ e a r d hfor the Structure of Proteins". Wrinch proposed the cyclol hypothesis as a general feature of protein structure in 1936, and it received serious consideration a t the time. However, Wrinch zealoi~slypromoted her incorrect cyclol hypothesis for over 30 years. She persisted in this effort more than adecade after the sequencing of insulin by Sanger and formulation of the a-helix and &pleated sheet structures by Pauling, and even well after crystal structure determinations revealed or-helices in the globular proteins myoglohin and hemoglobin. I t is a gross exaggeration to claim. as do Wrinch and Julian. that the findine of a tetrahedral carbinol ciirhon in an ergot alknloid veriiies [he cvclol hyuothesis for nrotrin structure. Contrnrv to the third sentence'of the ~ u l i a article, i Wrinch did notdedicate her life to the solution of the architecture of protein molecules. Instead, she dedicated her life to promoting tirelessly her failed cvclol hvpothesis. ~ r i n c hdoeynot serve as a role model, because she was distinctly unscientific. With an emotional commitment, she pursued an incorrect hypothesis relentlessly, donning a mattyr's role in the process. It is not that there should he more cyclol structures in nature as Julian suggests, hut rather that Wrinch should have redirected her energies toward investieations of the structures that do occur in nature. It is not necessary to advance Wrinch as a role model. Dorothy Crowfoot Hodgkin, Gerty Cori, and Rosalyn Yalow, all of whom won Nobel Prizes in similar or related fields, and many other women scientists provide examples of careers that we all would like to emulate. R. Bruce Marlln
University of Virginia Charloiiesvilie.VA 22901
Le ha teller-Right or Wrong?
frequently found in undergraduate chemistry textbooks. A more detailed treatment of this subject can he found in K. Denhigh's The Principles of Chemical Equilibrium, Cambridge University Press, 1971. Gustavo Qulntero B.
Universidad de Antioquia Departamento de Cwimica A. A. 1226 ~edellin.Colombia
To the Editor:
Quintero brines - uu. an imwxtant m i n t (which. incidentally, i never fail to stress in my classes). He is quite right in that. strictlv s~eakine. -. the "thermodvnamic eauilihrium constant" &en by Ln K = -AG0/RT
(1)
is dimensionless. However, a given numerical value of this constant is all hut meaningless unless the standard states and stoichiometry of the reaction are stated as well. For the ammonia reaction, for example, the value will differ depending on whether the standard states are 1 atm, 1 kPa, 1 psi, or 1 Torr and whether the reaction is written as
For the engineer, the dimensional constant, to whose use Quintero as thermodynamic purist objects, is much more practical. Because the standard pressures in the thermodynamic constant are unity by definition, the practical constant has the identical numerical value, and its dimension gives all necessary information on standard states and stoichiometrv. For instance. for the ammonia reaction. the dimension km-1 clarifies that the standard states are taken as 1 atm and that the secondof the two stoichiometriesahove is used (the dimension would he for the first). (Of course, if the reaction entails no change in mole numher, even the practical constant is dimensionless.) From this vantage point one might perhaps observe that the "error" so common in our chemistry textbooks is not the use of the practical, dimensional constant hut the failure to explain its exact relation to the thermodynamic constant in eq 1 above. Of this omission I have been guilty also in my article on the Le Chatelier principle. F. G. Hemerich
TO the Editor:
In the article: "Le Chatelier-Right or Wrong" [1985,62, 3051, it appears on page 306, just after eq 2: "The resulting conversion for some selected mole ratios, with KT = 1.413. atm-I . . ." I t is well known from thermodynamics that equilibrium constants are always dimensionless. This can he seen from the relation
where KTO is a pure number. For the reaction mentioned by the author in his article, %N2+8hH2=NH3
the equilibrium constant has to he written as follows:
If the partial pressures are in atmospheres, then po = 1 atm, and the units cancel out. Therefore, the equilibrium constant is dimensionless. I would like to point out that this is a common error,
Department of Chemical Engineering The Pennsylvania State University University. PA 16802
New Stolchlometry for Copper Dlssolutlon In Nltrlc Acld To the Editor:
I t was indicated in the reaction described by F. M. ElCheikh, S. A. Khalil, M. A. El-Manguch, and Hadi A. Omar [1985, 69, 7611 that copper(I1) nitrate, nitrous acid, nitric oxide, and water are the products of the copper-nitric acid reaction with the indication that nitrogen dioxide does not aunear .. to be a ~ r i m a r vproduct in this reaction. The halancing of thekquation for this reaction with a, b, m. x . Y, and z was of more interest than the mechanism for t h i < r e x t ~ o nand the atatemrnr rnncerning nitrogen di~~xide. B y taking into account that cower is oxidiztd frum zero to .. plu;tw
