Lab Manual - eScience Labs

Appendix: Good Lab Techniques
• Use test tube caps or stoppers to cover test tubes
when shaking or mixing – not your finger!
• When preparing a soluon, refer to a protocol for
any specific instrucons on preparaon. Weigh out
the desired amount of chemicals, and transfer to a
beaker or graduated cylinder. Add LESS than the
required amount of water. Swirl or sr to dissolve
the chemical (you can also pour the soluon back
and forth between two test tubes), and once dissolved,
transfer to a graduated cylinder and add the
required amount of liquid to achieve the final volume.
• A molar soluon is one in which one liter
(1L) of soluon contains the number of grams equal to its molecular weight.
• Ex:
1M = 11g CaCl x 110g CaCl/mol CaCl
(The formula weight of CaCl is 110g/mol)
• A percent soluon can be prepared by percentage of weight of chemical to 100ml
of solvent (w/v) , or volume of chemical in 100ml of solvent (v/v).
• Ex:
20g NaCl + 80ml H 2 O = 20% w/v NaCl soluon
• Concentrated soluons, such as 10X, or ten mes the normal strength, are diluted
such that the final concentraon of the soluon is 1X.
• Ex:
To make a 100ml soluon of 1X TBE from a 10X soluon:
10ml 10X TBE + 90ml water = 100ml 1X TBE
• Always read the MSDS before disposing of a chemical to insure it does not require
extra measures. (provided on www.eScienceLabs.com)
• Don’t pour unused chemical back into the original bole.
Disposable pipets aid in accurate
measuring of small volumes of
liquids. It is important to use a new
pipet for each chemical to avoid
contaminaon.
• Avoid prolonged exposure of chemicals to direct sunlight and extreme temperatures.
182