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
reagents: a hygroscopic solid that gets liquidy in air,
0.05 mg of catalyst, a liquid that clogs syringes and must be distilled
use, and your
precious reactant, which is heat and acid sensitive. The reaction must be done at
using a complex glass apparatus, and requires three flasks for successive dropwise
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
If the reaction is moisture or air sensitive, oven- or flame-dry the flask and
run the experiment under an inert atmosphere.
Purify your reagents and solvents, if necessary.
Locate syringes and needles of appropriate size, if necessary.
Weigh your reactants, into your reaction flask, onto weighing paper, or into a
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
weigh sensitive reagents until just before use.
Allow compounds from the refrigerator to warm to room temperature before
to avoid undue exposure to air.
To weigh a liquid:
Using the density of the liquid, calculate the volume of liquid and use a
Weigh an empty syringe, fill the syringe, and weigh again.
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
and remove 1 mL. You can remove the solvent to check the weight. This method is
than you might think.
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