Originally posted on Chemtips:
Working on the microscale has many advantages. Workups take less time and are easy to do in parallel, heating and cooling is much more efficient, and 200 mg of intermediate lasts 10-20 reactions or more. I’ve already covered my favourite glassware for such reactions in an earlier post (vial chem), but there’s a whole set of skills necessary for measuring trace amounts of material that don’t come into play on the gram scale.
Solids to be weighed generally fall into one of three categories. The easiest to work with are small, free flowing granules that slide from spatula to weigh paper to vessel without leaving significant traces behind (potassium carbonate is a typical example). Crystalline materials are a little more challenging, as stray static charge usually holds them to both spatula and weigh paper, necessitating a quick rinse to “help” the residue into the reaction vessel. Gummy solids and hygroscopic materials are the worst, as both are difficult to scrape from their original container, and tend to hold tight to the weigh paper and spatula. With a gummy solid the usual solution is simply to dissolve the compound in a suitable solvent and transfer it via syringe or pipette.