Chapter 3: Equipping a Home Chemistry Laboratory 19IPLOSIOM n DAnGER
Filtering flasks are considerably more expensive
than standard Erlenmeyer flasks. Don’t attempt to
save money by building your own filtering flask with
a standard Erlenmeyer flask and a two-hole rubber
stopper. Filtering flasks are built of thick glass to
resist air pressure when they’re evacuated. A standard
Erlenmeyer flask is much more fragile, and may implode
when evacuated, scattering broken glass and chemicals
all over the lab (and you).
Some experimenters construct filtering flasks with
standard Florence flasks, which are more strongly built
than Erlenmeyer flasks and less likely to implode, but
we strongly recommend against this practice. If you
need a filtering flask, buy a filtering flask. Don’t attempt
to make do.
Always clamp a filtering flask securely while it’s in use.
Otherwise, it may tip over and shatter, scattering glass
and chemicals.z
colors. But even if your interest in bottles is merely utilitarian,
you’ll probably want to acquire a lot of them in many different
sizes and types.
SToRAGE BoTTLES
Storage bottles, shown in Figure 3-10, are used for stock
solutions and other general storage. If you work mostly with
chemicals from their original containers, you’ll need fewer
storage bottles; if you make up stock solutions of commonly used
chemicals, you’ll need more. I prefer the latter method, because
it’s faster, more convenient, and more precise to measure small
quantities of stock solutions rather than weighing out individual
chemicals each time they’re needed.
You don’t have to buy storage bottles, of course. You can
recycle empty household containers. For larger bottles, one good
source is empty 500 mL soda bottles, which are made of resistant
polyethylene terephthalate plastic and have tight-fitting caps.
(Don’t use them to store organic solvents, concentrated acids
or bases, or other chemicals that might react with the plastic,
but dilute stock solutions of most inorganic chemicals are fine.)
Before you reuse them, wash recycled bottles thoroughly with
soapy water, soak them in a bleach solution (one part chlorine
bleach to five parts water), and then rinse them thoroughly
and allow them to dry until no odor of bleach (or anything
else) remains.
If you decide to buy storage bottles, you’ll find them readily
available in glass and various plastics in sizes ranging from 15 mL
(0.5 ounce) or smaller to 1 quart/liter and larger. For general use,
I prefer standard flint-glass narrow-mouth bottles in the styles
called French Square and Boston Round, with plastic caps. Such
bottles are commonly available in colorless or brown (amber)
glass, and, less commonly, in blue glass. (Blue glass bottles
were historically used to store poisons.) Brown glass bottles are
usually less expensive than similar bottles in colorless glass,
presumably because making colorless glass requires using purer
and more expensive materials. That’s just as well, because some
stock solutions are light sensitive, and should be stored in brown
or amber glass. It doesn’t hurt to store any solution in a brown
glass bottle, so that’s what I generally use.
Before you buy storage bottles, think about the quantities of
stock solutions you’re likely to make up for your lab. For my lab, I
decided to make up 100 mL of most stock solutions, so I ordered
most of my bottles with that in mind. As it turned out, 4-ounce
(118 mL) bottles were considerably less expensive than 100 mL
bottles, so I ordered 100 4-ounce bottles. I also wanted to make
up 500 mL of commonly used stock solutions such as dilute
acids and bases, so I decided to order two dozen 500 mL bottles
as well. Once again, pint (473 mL) bottles turned out to cost less
than the 500 mL metric equivalent, so I ordered pint bottles
instead of the 500 mL ones. Pint bottles are too small for 500 mL
CEARH pE LoCALLy ANd By THE CASE
General laboratory supply vendors sell bottles, but they are
often quite expensive, particularly if you buy only a few at a
time. Also, shipping charges may be very high. Check your
local Yellow Pages under “Bottles” for local vendors, and
you may be surprised. For example, we bought a case of
4-ounce amber glass storage bottles with plastic caps for
less than $0.40 each.FIGURE 3-10: A selection of storage bottles