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General Lab procedures
For the preparation of a solution
First, get all the materials necessary on the work bench. This will include: electronic scale, chemicals, spatulas and tweezers, gloves, caped tubes, racks, weighing paper and boats, etc.
First it needs to be leveled out with respect to the work bench. To assure it is, take a look at the bubble indicator. If it is not centered, move the knobs located in the four bottom corners of the scale. Unfortunately, to operate the four knobs is not an easy task and the best way to operate is to guide the bubble in the two possible inclination planes.
Second, the scale is very sensitive. Therefore, when taking measurements the two side-doors need to be closed and you need to avoid any harsh moves around the scale.
The side doors are only open for more freedom for the hands when placing the chemical into the scale.
First, clean them following the protocol. (Check the section “Cleaning” in the following link:Cleaning)
Second, let them sit on paper towels on top of the work bench. Also, they should remain covered to avoid contamination.
Once they have been in contact with a chemical, they cannot be placed just in top of the counter or paper. The proper way to place them while working on something else is as the following picture indicates.
Do the measurement of one chemical at a time. Choose which one you are going to work with and stick to it until you finish.
NOTHING can be placed inside the stock solution container. This way we avoid possible contamination. Thus, reasonable amounts of the chemical need to be poured in separate weighing boats.
To see how to handle these two, check the section How to properly weigh a sample in the following link:How to weight a sample
Moreover, try to hold them from the edges, as far as possible from where the sample is going to be placed.
Transferring the sample
Once you have all the needed chemicals they need to be placed on a tube.
Carefully remove the weighing boat from the scale and form a subtle cone shape with it. Place the tip vertically inside the tube and then with the help of a spoonula, push the entire chemical down until most of it is poured.
If you are using the wax paper the procedure is similar, with the advantage that the wax paper has already a crack and serves as a canal directed to the tube.