Reactions: Letters

[LEFT] Maraschino cherry ice cream made at Penn State. [CENTER] An artist's rendition of a DNA structure. [RIGHT] Mildred Cohn

Blind Flavors

Science by the Scoop” (CH, Summer 2010, pp. 40-41) brings to mind my work in developing ice-cream flavors in my consulting days 60 years ago. What surprised me was how difficult it was to distinguish one flavor from another in a blindfold test in the absence of associated color, which is why most commercial ice creams use color additives. Try this blindfold test at home; it may surprise you, too!

Saul Ricklin, Bristol, Rhode Island



The article titled “The Dream in the Machine” (Summer 2010, p. 17) about my “favorite computer,” the IBM 701, was indeed flattering and is mostly factual. However, I write to correct the impression that our theoretical work with the 701 had any significant impact on the commercial success of Dacron.

Upon my arrival at DuPont’s Jackson Laboratory in late 1950, I was almost the only physical chemist among perhaps 200 organic chemists, many of whom were engaged in creating dyes for the “new” fibers, such as Dacron, Orlon, and the earlier Nylon. I had proposed to provide guidance to this synthetic effort by elucidating the relationships between color and structure through use of molecular orbital theory. This effort, in collaboration with my consultant and former teacher, Robert G. Parr, led to the development of the PP (Pariser, Parr) molecular orbital theory, which was later added to by John Pople, and is now known as PPP.

Although the use of PP provided occasional guidance to the synthetic dye effort at Jackson Laboratory, I am sure that it was not a factor in the commercial success of these fibers. However, the publications of PP theory were extremely well-received worldwide, resulting in these papers being among the five most cited in chemistry or physics during 1961–1977. They likely had influence over various other applications, such as fluorescent dyes, organic LEDs, and conductive polymers.

Rudolph Pariser (via e-mail)


The Dream in the Machine” implies that DuPont’s Dacron was a new fiber. Poly (ethylene terephthalate) was first produced by Calico Printers and was commercialized by Imperial Chemical Industries in the United Kingdom. DuPont cross-licensed nylon 6,6 to ICI in return for a polyester license. DuPont built a plant in Kinston, North Carolina, to produce Dacron, their version of ICI’s Terylene. The U.S. Justice Department did not look favorably on DuPont using one patent monopoly (Nylon) to gain another and so DuPont granted a nylon license to Chemstrand, a fledgling fiber company originally formed to produce an acrylic fiber (Acrilan). Acrilan was shut down several years ago and the nylon business sold to SK Partners. DuPont is also out of the polyester and nylon businesses except for the aromatic nylons Nomex and Kevlar.

Jim Masson (via e-mail)

Creative License

The summer issue of Chemical Heritage magazine arrived and went to the top of my reading list. Well done, as always. One thought, however: When artists get hold of a chemical structure or formula, they often stylize it or alter it artistically to their liking. The DNA structure is right handed while the artist’s rendition on p. 39 is a left handedhelix. Not a big deal to the casual reader but, after all, this is Chemical Heritage magazine. The saving grace here is that it is labeled as an artist’s rendition. Keep up the good work. The publication is making a powerful impact on the CHF reputation and branding.

Jerry Gallwas (via e-mail)

Editors’ note: While we have a wonderful collection of chemistry-related images and objects, we often have to search long and hard for other images—such as that of the DNA strand—that are suitable in size and subject matter for the magazine. In this case, to avoid confusion we should have added that the DNA structure is right handed in nature, if not in art.


Cohn’s Story

I enjoyed reading your article on Mildred Cohn, “A First Lady of Chemistry” (Summer 2010, p. 13). While academic tenure was not granted to Dr. Cohn until she moved to the University of Pennsylvania, the opportunity for her career to flourish as an independent research scientist began during her time at Washington University in St. Louis in the Cori department. Her connection with the American Heart Association began in 1953 as one of the early recipients of the AHA’s Established Investigator Awards. She appeared as first or second author on all but one of the 14 papers that she published while at Washington University. At the time of her departure she held the title of Research Associate Professor. On a separate point, her research did not help to determine the structure of ATP but rather to determine the mechanism of reactions that use ATP.

Michael A. Grayson (via e-mail)


Element 112

I have just received the summer issue of Chemical Heritage and as usual the magazine contains a number of interesting articles about a range of topics. Being heavily involved in the preparation of the International Year of Chemistry at various levels, the short piece about “It’s Elemental” drew my attention. The article, which informs about a video competition to be launched by CHF this fall, is accompanied by a periodic table with the chemical symbols for all the 112 elements approved to date. 

Unfortunately, the symbol for element 112, copernicium, is wrong. The symbol shown, Cp, has indeed been proposed for this element, but instead Cn was chosen. The principal reason for rejecting Cp was that it was used as the symbol for cassiopeium until IUPAC in 1949 approved the name lutetium (Lu) for this last of the lanthanide elements. Another argument against Cp was the fact that this symbol has been used for decades as notation for cyclopentadienyl. Finally, it has also been noted that CP is used as the symbol for heat capacity at constant pressure. 

So CHF, please correct the mistake before the contest is launched this fall, and please, keep up the good work.

Leiv K. Sydnes, University of Bergen (Norway)

Editors’ Note: The erroneous image came from an early design of the Web page, which depicted an outdated version of the periodic table. A current version was used during the programming phase of the online contest several months ago. Unfortunately, the magazine used the earlier promotional image, and the error was not picked up during the editing process. The contest is now live and we hope our readers will visit the Web page, view the videos, vote, and leave comments.


Brazil Connection

One aspect of John William Draper’s life (“Across the Spectrum,” Summer 2010, p. 8) is little known. Draper was married to a Brazilian woman whose British father was a professor of chemistry in Rio de Janeiro and whose mother was a lady-in-waiting to the Portuguese queen. In 1808 the Portuguese royal family, fleeing Napoleon’s invasion, took refuge in Brazil, thus making Rio de Janeiro the de facto capital of the Portuguese Empire. They remained in Brazil for 13 years, during which time many institutions were created, several of them dealing with science. This includes the Royal Military Academy, where the first regular course of chemistry in the country was set up in 1810. The professor appointed to the chair of chemistry was Daniel Gardner, who married a lady-in-waiting and namesake of the Portuguese queen, Carlota Joaquina de Paiva Pereira Gardner. After Gardner’s retirement in 1825 the family went to England, where their daughter, Antônia Caetana de Paiva Pereira Gardner, would later marry John William Draper.

Carlos A. L. Filgueiras, Department of Chemistry – UFMG (Belo Horizonte - MG Brazil)

Editors’ Note: On page 30 (“Chemical Relations,” Summer 2010) Walter Hückel is listed as the theoretician who proposed a general theory based on the number of electrons in a ring compound. In fact, it was his brother Erich who proposed the theory. We regret the error.