Explosive lsopropanol To The Editor:
"Safety A1ert"in the September 1983issue of the JOURNAL informs of an explosion of isopropanol. I had a similar accident when distilling the contents of an old bottle of isopropanol. The explosion t w k place at the end of the distillation, when the "tail" contained a high concentration of peroxides formed during long storage (3-4 years) in- the ~ ~-~~stockroom. The fourth edition of Vogel's "Textbook of Practical Organic Chemistry" (p. 270) gives a method for purifying isopropanol and directions for testing and removal of its peroxredevelo~sdurineides. warnine that "neroxide eenerallv " several days." The formation of ~eroxidesfrom iso~rooanolis. eenerallv. not described in organic chemistry textbooks \th&retical ;r ursctiral I. Since the hazards of its distillation are no1 known t,, students and many instructors, clearer warnings in textbooks and laborntorv mnnunls would he desirable. ~
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envision the square for He being next to the square for H instead of with the noble gases, 2) know the mechanics of reading, i.e., have his eyes follow the horizontal lines from left to right before drovdnz to the next 1)
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row, 3) be able to subtract 1 and 2 from a number
For the use of the chart, n is the number of the row. The lanthanide and actinide series are inserted, mentally, where indicated. As far as the exceptions go, they are still unaccounted for. However, I tell the students there are no d4's or d9's in neutral atoms. Where they would occur, an electron comes out of the previous s to bring it to a d5 or dlO. The next electron refills the s, and then the order resumes. I realize some other exceptions occur, but I tell the students not to worry about them. As I said, I have found that my students pick this up very quickly and I teach it in the first year of high school chemistry.
' Term used by Dave Robare. North Seattle Community College.
Jullo ~ a n i e Bonafede
John M. Leach
Facubad de Farmacia y Bioquimica Universidad de Buenos Aires Buenos A i m , Argentina
Agua Fria Union High School Avondale. AZ 85323
Ediior's -- ~. .Note:
We also have received an informal commentary from Leslie Eretherick suggesting that such explosions might result from the peroxidation of ketonels) present as trace contaminank in the isopropanol. This is a possibility if the made e l m by fermematian a pebochemicaliy isapropanol were an old -le from propene, when traces of 2-butanone could be formed. He refers to page 447 of his "Handbaak of W d a u ! Chemical Reactions," 2rd ed.. Butterwams, 1979 lor relevant detads of the peroxidation mechanism. (MMR)
E-Z S, p
To the Editor: In his article, "4s, 3d, What?"in the July 1983 issue of the JOURNAL, A. Kurtz Carpenter pointed out the need for students to have a simple method for remembering the filling order of orbitals. He reviewed the Uncle Wiggly system' and then proposed his own variation. I agree with the need, but I do not see the necessity of learning or memorizing a crutch. If the crutch, or system, is misdrawn, then it is, of course, useless. I have heen using a method for teaching the filling order for 24 years and have done so with great success. The method I use is based w o n somethine with which everv chemistry student is familia; and is highG visible in ever; science classroom. The item is the extended form of the Deriodic table. As long as the table and the symbols of the k e ments are visible, the student need not he ahle to see atomic numbers nor anything else. The student needs to be ahle t o do only three things:
Making Candy with Enzymes
To the Editor: The article by Harriet Friedstein, Basic Concepts of Culinary Chemistry, (J. CHEM.EDUC.,60,1037 (1983)), was most interesting and informative. The chemistry of candy-making is also of interest to students a t all levels of education. In the introduction to my lecture on therapeutic uses of enzymes, which I give to all first-year medical students, I ask them to consider the following problem: How is a liquid-center, chocolate-covered cherry made? (This is a candy which has a cherry floating in a sugar solution and the whole is covered with chocolate.) At the end of the lecture I tell them how the candy is made. The cherry, a portion of sucrose paste, and invertase are covered with chocolate and allowed to incubate. The sucrose is converted to a solution of glucose and fructose, and the concentration of glucose is high enough to suppress bacterialgrowth. I have also raised the question: Why can't Jellom he made with fresh pineapple chunks hut only with canned pineapple chunks? The answer is supplied when I discuss collagen structure and function. Donald M. Kirschenbaum DepaRment of Biochemistry State University of New Yark Downstate Medical Center 450 Clarkson Avenue Brwklyn, NY 11203
