Tartaric Acid
To the Editor: Two errors need to be corrected in the recent article by Gordon W. Wood IJ. Chem. Educ., 52, 177, (1975)l in which he makes the'excellent proposal that there be " ~ e discovery in a Course for Nonscientists." Possibly through a typogriphical error, Mitscherlich's paper on sodium ammonium paratartrate was dated forty years too late. Tbe correct date is 1844 [Comptes Rendus XIX, 720 (1844)l. More serious is the error in the statement that "paratartaric acid," as it was then called, is meso-tartaric acid. Pasteur separated the enantiomorphic crystals from sodium ammonium paratartrate and regenerated the d - and 1-tartaric acids. I t is remarkable that Pasteur was able to design experiments from which he deduced that the molecules were opposite in form, because he did not even know the correct molecular formula. much less the structural formula. Although his analytical data were correct, he used the atomic weights C, 6: H. 1; and 0.8 to obtain the molecular formula. i t that time meso-tartaric acid was unknown. Pasteur reported meso-tartaric acid for the first time in 1853 [Comptes Rendus XXXVII, 162, (1853)] when he made dl-tartaric acid by heating an aqueous solution of the cinchonidine salt of d-tartaric acid for several hours a t 170°C. We now recognize that the d-tartrate first formed the meso-tartrate by the inversion of either one of the asymmetric carbon atoms, and the meso-tartrate was then converted randomly to d - and 1-tartrates by a second inversion. Pasteur's final mixture probably contained an equilibrium mixture of meso-, dextro-, and leuo-tartrates. Phillips Academy Andover, Massachusetts 01810
Thomas Rees
To the Editor With severe embarrassment I must admit that the letter of Thomas Rees is correct on both points raised with respect to [J. Chem. Educ., 52, 177 (1975)l. The typo which moved Mitscherlich's paper from 1844 is perhaps most significant in creating misunderstanding about the context in which Pasteur's work was done. In particular, his anticipa-
752 / Journal of Chemical Education
tion of certain aspects of the idea of tetrahedral carbon is lost by this error. The confusion created by the error in the caption of Figure 1 and the accompanying text is more difficult t o correct. Complete correction requires changes beginning with the last full sentence of column 1, p. 177 and continuing to the end of the paragraph. Figure 1shows models of the meso form and the enantiomeric pair of tartaric acids. Mitscherlich's active material corresnonds to a pure enantiomer (called "tartrate (double) of soda and ammonia" in the above quotation). Paratartrate (also called "racemic acid") corresponds to an equal mixture of the two enantiomers. The caption of Figure 1should then be altered to read: Figure 1. Models representing meso and active tartaric acids. The tartrate of Mitseherlich corresponds to one of the active forms, while the paratartrate corresponds to an equal mixture of the two (see reference 2). Gordon W. Wood University of Windsor Windsor, Ontario N9B 3P4. Canada
Thermodynamics and Song
To the Editor: Dr. W. L. Smith has pointed out, in his recent entertaining article [J. Chem. Educ., 52.97 (1975)], how the concepts of thermodynamics can be found in many popular songs. There is one popular song that has thermodynamics as its major theme. It is "First and Second Law," written and sung by Michael Flanders and Donald Swann, and available on a record ("At the Drop of Another Hat," Angel 36388). The authors have degrees in History and Modern Languages, but have accurately expressed the meaning of the "Laws" in a delightfully witty way!
Brian D. Kybett University of Regina Regina, Saskatchewan. S4S OA2 Canada
