I would not normally review an app that is mainly a product catalog, but the Aldrich Handbook of Fine Chemicals is not simply a product catalog to biologists and chemists. In many instances, it is the beginning of a new research project (the so-called “Sigma screen”). And boy is it nice to have that heavy tome in iPad form. The homescreen has two viewing options: users can either view chemical structures in a grid pattern, alphabetically arranged (much akin to the catalog format), or they can display the chemical names and chemical compositions in a list on the left side of the screen. This second option leaves the right side of the screen free to display the menu for the other features of the app, which include a periodic table, a metric conversion chart, fundamental physical constants, and a particle size conversion chart, among others.