The Setup

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A Perfect Reaction (see all): You do not make errors in your calculations, you do not need special equipment, you have clean, dry glassware, and you do not need to purify reactant, reagents or solvent.

A Nightmare Scenario (see all): You need to weigh four different reagents: a hygroscopic solid that gets liquidy in air, 0.05 mg of catalyst, a liquid that clogs syringes and must be distilled immediately before use, and your precious reactant, which is heat and acid sensitive. The reaction must be done at -30 C under argon using a complex glass apparatus, and requires three flasks for successive dropwise addition via cannula.

Common Rookie Mistakes: The Setup

Step by Step:

  1. Locate a clean, dry flask, a stirbar, a septum and any other apparatus necessary for the procedure. Calculate the total milliters of solution, and use a flask with at least twice that capacity.
  2. If the reaction is moisture or air sensitive, oven- or flame-dry the flask and prepare to run the experiment under an inert atmosphere.
  3. Purify your reagents and solvents, if necessary.
  4. Locate syringes and needles of appropriate size, if necessary.
  5. Weigh your reactants, into your reaction flask, onto weighing paper, or into a separate flask (a pointy flask is useful for reagents that will be added in solvent). Consult your procedure to see what is necessary. Do not mix anything yet, and do not weigh sensitive reagents until just before use.

Tips (see all):

    1. Using the density of the liquid, calculate the volume of liquid and use a syringe.
    2. Weigh an empty syringe, fill the syringe, and weigh again.
    3. If the liquid is in a flask, and you only need a fraction of it, try this: if you have 90 mg in the flask, and you need 30 mg, dissolve the material in 3 mL of solvent, and remove 1 mL. You can remove the solvent to check the weight. This method is more accurate than you might think.
    4. For small amounts of viscous liquids, weigh an empty pipette, dip the tip in the substance,and weigh again. This is not a generally useful method, but good sometimes.

See also: Rookie Mistakes, How to Improve Your Yield, How to Handle, How to Work on a Small Scale, Weighing Problematic Reactants and Reagents, How to Use a Syringe