36 DIY Science: Illustrated Guide to Home Chemistry Experiments
The risk of that practice is nil, because I always use a new
scoop (or at least one that has been thoroughly washed) each
time I transfer chemicals from the original bottle. For transferring
small quantities of chemicals, use a modified Beral pipette.
Trim the bulb end diagonally to make a disposable scoop. For
transferring larger amounts of chemicals, use a disposable plastic
spoon, which you can find in the picnic supplies section of the
grocery store. (Or, if you’re cheap like I am, save the ones you get
at fast-food restaurants.)
Some chemicals tend to form solid masses in the bottle, making
it difficult or impossible to scoop them out with one of these field-
expedient plastic scoops. In that situation, use a standard stainless-
steel spatula or an ordinary stainless-steel teaspoon or soup spoon.
Wash the spatula or spoon afterward, rinse it in distilled water, and
put it aside to dry thoroughly before you reuse it.
FLTERPI APER
Filter paper is used with a standard or Büchner funnel to
separate solids (the filtrand) from the filtrate (the liquid you’re
filtering, also called the supernatant liquid). Filter paper is sold
in precut circles of various sizes to fit different size funnels. The 9
cm or 11 cm size is most useful in home labs.
There are many varieties of filter paper with different
characteristics. Quantitative filter paper is pure cellulose
with almost no mineral content. It is used in quantitative tasks
because when it is heated to combustion, it leaves almost zero
ash to contaminate (and add weight to) the filtrand. Qualitative
filter paper has a higher mineral content, but is less expensive
and suitable for most uses.
Filter paper also differs in the tightness of its fibers, which
determine both its flow rate (filtering speed) and its particle
retention size. Coarse filter paper offers a very fast flow rate,
typically captures particles 20 μm (micrometers, 0.001 mm)
or larger, and is suitable for filtering coarse or gelatinous
precipitates. Medium filter paper has a moderate flow rate,
typically captures particles larger than 5 μm to 10 μm, and is
suitable for general lab use. Fine filter paper has a low flow rate,
typically captures particles larger than 1 μm to 3 μm, and is
suitable for capturing the finest precipitates.
Ordinary unbleached coffee filters substitute adequately for
formal filter paper for most home labs. Coffee filters have a
high flow rate and correspond roughly to coarse laboratory
filter paper.
CROMATOGRAPHYH PAPER
Chromatography paper has special characteristics that optimize
it for chromatography. The type of fibers used and their length are
carefully controlled, and the production process is designed to
orient the fibers parallel to minimize spreading of the sample as
the solvent carries it along the paper. Chromatography paper is
sold in rolls, large sheets, and small strips, of which only the last is
reasonably priced for home lab use.If you don’t have chromatography paper, you can substitute
sheets or strips of ordinary 100% cotton bond writing paper,
making sure to orient the grain of the paper parallel to the
direction of the solvent flow. The results aren’t quite as good
as they would be if you used actual chromatography paper, but
they’re usable for most purposes in a home lab.BTTERYA AnD ELECTRODES
To complete the electrochemistry labs in this book, you’ll need
a power supply, a selection of electrodes, and a set of leads with
alligator clips. An ordinary 9V battery works fine for the power
source. You can buy the electrodes or make your own, as follows:Carbon
Use a bundle of several mechanical pencil “leads,” which are
actually graphite.Aluminum
Cut strips from an aluminum beverage can. Use sandpaper
or a similar abrasive to polish the surfaces to remove paint,
oxidation, and plastic coatings.Copper
Heavy-gauge copper wire salvaged from a scrap piece of
Romex works well, as does a flattened section of copper tubing.Iron
A large iron or steel nail or bolt works well. Polish the surface
with sandpaper before you use it. Make sure that whatever you
use is not galvanized, or you’ll actually be using a zinc electrode
instead of an iron or steel one.You’ll also need electrodes of lead, magnesium, nickel, tin, and
zinc, which are best purchased from a laboratory supply vendor.RSBBERU TOPPERS AnD CORKS
An assortment of rubber stoppers and corks is useful for
sealing test tubes and flasks, constructing apparatuses, and
so on. Rubber stoppers are popular because they are durable,
reusable, provide a good seal, and are available in solid, 1-hole,
and 2-hole versions.Unfortunately, there is little standardization in the sizes of rubber
stoppers or the stopper size required to fit vessels of particular
sizes. One vendor’s #2 stopper may be the same size as another
vendor’s #3 stopper, for example, and two 250 mL Erlenmeyer
flasks from different vendors may require different stopper sizes.