320 DIY Science: Illustrated Guide to Home Chemistry Experiments
CUTIOA nS
Be careful with the laser pointer. Although standard 1 mW
Class 2 laser pointers are reasonably safe to use, you
should never look directly into the beam. (And be cautious
about specular reflections, too. A beam accidentally
reflected off something shiny can be as hazardous as a
direct exposure.) Although none of the chemicals used
in this laboratory session are particularly hazardous, it’s
always good practice to wear splash goggles, heavy-duty
gloves, and protective clothing. Discard all food items
when you are finished; do not consume them.z
EvRdE y Ay CoLLoIdS ANd SUSpENSIoNS- The protoplasm that makes up our cells is a complex
colloid that comprises a dispersed phase of proteins,
fats, and other complex molecules in a continuous
aqueous phase. - Detergents are surfactants (surface-active agents)
that produce a colloid or suspension of tiny dirt
particles in an aqueous continuous phase. - Photographic film consists of an emulsion of gelatin
that serves as a substrate for a suspension of
microscopic grains of silver bromide and other light-
sensitive silver halide salts. - Many common foods, including nearly all dairy
products, are colloids or suspensions. - Toothpaste, shaving gel, cosmetic creams and lotions,
and similar personal-care products are colloids. - Water treatment plants use flocculants (chemicals
that cause finely suspended or colloidal dirt to clump
into larger aggregates and settle out) as the first step
in treating drinking water.