BASIC SOLUTION PREPARATION
Each student will have two or three solutions to prepare for the class. The solutions will live at your
bench, but will be available to all other student. There would be value in learning to make all of the
solutions listed here, but we don’t have the time, and it would be wasteful. You should, however pay
attention to the issues surrounding each one (I will talk about those in lecture) and make sure you
know how to do the relevant calculation
Basic Solution Preparation – “How To”
1. Write name of solution, and date it is being prepared, as a title in your lab notebook. (You do not
need to write a purpose, it is obvious)
2. For solutions with more than one component, list the ingredients, and the final concentration of
each.
3. Find the reagents. Record the FW – (not strictly necessary if doing a % concentration, but can be
helpful to verify that the correct reagent was used)
4. Do the calculations. Include them in the book
5. Get H2O and beaker and set stirring—record the kind of water and volume used to start. [Use
Millipore water (unless it is unavailable). House deionized is an acceptable second choice for
most solutions]
6. Weigh out reagent, and add it to the water.
7. Record:
manufacturer,
catalog # (not CAS, that’s different) and
amount actually weighed
serial number of balance used
lot #
8. Repeat steps 6 & 7 for each reagent. If you are adding a stock solution instead of a commercial
reagent, record the initials, date of the preparation of the stock and the identity (e.g. 4 M NaCl, or
10X TBE). You generally need not record the sort of glassware or pipette used toe measure it.
9. When (all components are) dissolved, adjust the pH if necessary. Keep in mind that the acid or
base that you use to adjust the pH becomes a component of the solution, so its product
information must also be included!
10. Decant into a graduated cylinder (leave the stir bar behind!) [in some labs you might use a
volumetric flask]
11. BTV (or q.s.) to desire volume. (“bring to volume”; “quantum sufficient”0
a) You may wish to use water you have first put into the beaker, to bring along whatever
solution had been left clinging to the sides of the original beaker. This is especially important
with higher concentration solutions!
b) If the volume ends up going over the targe (which can happen if you started with too much for
the crystal + pH-ing volume), you will neither eed to recalculate and re-label the solution, or
fix it (by adding some more solute and adjusting the volume to a new final) or remake the
solution.
NOTE: Some solutions will be of relatively small volume, difficult to bring to final volume. In such
circumstances it is permissible to add the final volume of solvent (water usually) to the dry solute.
(For example, if you weigh out 54 mg for a 10 mg/mL solution of BSA, it would be difficult to “bring
to volume” for 5.4 mL, and 54 mg will not contribute much volume. So just add 5.4 mL of water to
the 54 mg.) However, do not record this as a “BTV” or “q.s.”, because this would suggest that you
did use your final volume as your endpoint measurement. Instead, record it as “To 54 mg of BSA,
added 5.4 ml of MQ H2O”.
12. Pour the completed solution into the storage vessel, labeled with the name of the solution:
a)
Include your initials and date -- that will reference them to the place in you notebook
where the lot numbers and calculations can be found! Do not label it with the
volume. As soon as someone uses some of the solution, that number will be false.
(Exceptions are when you make small aliquots (portions) that are meant to be single
use containers)
b)
USE TAPE on glassware and non-disposable bottles-- do not write directly on the
white label. Do not put the tape over the white label, or over the red dot.
c)
Use black sharpie. Colored Sharpies tend to be EtOH-soluble, and ball point pen isn’t
dark enough, and smudges
Additional notes:
Record any deviations from the basic procedure, or other notes that would be helpful to know next
time you make it (e.g., did you find out that you need to heat or adjust the pH to assist dissolution? If
so, it would be nice to have that written down !)
Make sure you know how solutions are to be stored (temperature, what container, etc.). For some
things the container matters (, and for some it doesn’t. If a solution needs to be autoclaved, or if it
tends to throw crystals or precipitates or get contaminated, glass is the best choice. Glass is not so
good for strong bases and some other things. Polyproplylene bottles are also available.
If a solution is stored any place other than your lab bench, it is wise to record where that is!