From "American Chemical Society Style Guide" for authors [1, pp. 356-357]:
The font (or typeface) is the style or design of the letters. There are
literally hundreds of fonts, but plain, simple fonts such as Helvetica or
Times Roman are best for scientific art. [...]
Use a clear type font, preferably Helvetica or Times Roman.
The software behind a font is covered by copyright law. Whereas
some copyright holders allow open access to their fonts, others exercise
some sort of limit. Publishers respect the copyright on fonts and will not
use a font without proper permission. [...]
TrueType is a font format designed by Microsoft for maximum legibility on a computer monitor, and it prints well on dot-matrix, inkjet, and laser printers. Microsoft permits free use of the fonts it provides (such as Times New Roman and Arial), but other companies that provide TrueType fonts may have use restrictions. TrueType fonts perform well in Web publishing, but they often pose technical problems in print publishing. TrueType fonts are ﬁne for producing GIFs, TIFFs, and JPEGs, as well as PDFs intended for the Web.
PostScript is a font format designed for high-end graphic arts. These fonts are designed for maximum legibility on paper and for maximum compatibility with high-quality, high-output printing equipment. PostScript fonts are generally covered by copyright and have limitations on their use. They seldom pose technical problems in print publishing, but the copyright issues may limit their usefulness in Web publishing. PostScript fonts are best for EPS ﬁles and PDFs intended for print.
OpenType fonts are a relatively new format intended to combine the
virtues of both TrueType and PostScript fonts.
STIX (scientiﬁc and technical information exchange) fonts were developed by a group of six scientiﬁc publishers to establish a comprehensive set of fonts that contains essentially every character that might be needed to publish a technical article in any scientiﬁc discipline. STIX fonts are available as a free download, under license, at www.stixfonts.org.
Good old Times New Roman indeed works quite decent, whereas Arial and Helvetica are probably one of the worst possible fonts for chemical formulas. STIX font family is nearly ideal, especially when you use (Xe)LaTeX. I personally like Linux Libertine and very similar Liberation Serif fonts, which are free and often pre-installed on various systems. The bottomline is, don't use exotic and/or non-free fonts, there are plenty to choose from.
- The ACS Style Guide: Effective Communication of Scientific Information, 3rd ed.; Coghill, A. M., Garson, L. R., Eds.; American Chemical Society; Oxford University Press: Washington, DC; Oxford; New York, 2006. ISBN 978-0-8412-3999-9.