These directions also apply to distilled water. After you have weighed out a sample in a flask or beaker, it is often necessary to let this sample stand until the next laboratory period. If you desire to cover the container and do not want any particles of cork, stopper, etc. to introduce an error in your analysis, plastic wrap of several types is provided for this use. The only items to be covered with plastic are those which have samples weighed into them and ready for the next period's use. The wrap is community property as are the scissors and neither should be removed from the south bench of the analytical chemistry laboratory.
Rubber bands are available.
There are a number of items of community equipment that is for your use, but are to be returned before you leave for the day. These items include pipette controls, tongs, label tape, plastic wrap, suction flasks and tubing, big burners, large graduated cylinders, and hot plates. I am sure there are other items besides the chemical reagents on the north wall of the laboratory. If you have questions please see the instructor. A final step in planning would be constructing a block diagram or flow sheet for the determination.