theycannotleap toconclusionson the basis of a singleexperiment.The only
way to be sure that particularconditions produce a particular result is to
repeatanexperimentover and over again. In science, being"sure"means being
able topredictwith only a small margin oferrorthatparticularconditionswill
produce particular results. Accuratepredictions can be made on one basis
only-repeatedexperiments.
SAFETY RULES
Yourlaboratoryis not a place to play.Experimentingis a serious business,
and you have tocarryitoutin a businesslike way if you are tolearnanything
from it. The rules belowwillhelpyou to enjoyyourexperiments and learn
from themwithoutendangeringyourselforothers.
Do not allowyourfriends to mix thingsjustto see what willhappen.Donot
do so yourself. Somecombinationsof chemicals aredangerousand you might
accidentally mix someofthese. Performonlytheexperimentsfor which you
havecompleteinstructions.
Always keep a good supply of tap water onyourlaboratorytable. Unless you
areworkingnear a sink, have awide-mouthedgallonjarfilled with water close
athand,as well as several large spongesforwiping up any chemicalsthatmight
be spilled.
If an acid or an alkali (base) is spilled on yourclothing,skin or any place in
yourlaboratory,immediatelywash the area with lotsofclear water.
AnAmericanRed Cross first-aidhandbookshouldbepartofyourlaboratory
equipment.Refer to it in case ofaccident,and neverhesitateto call adoctor
if you areaccidentallyburnedor inhaleirritatingfumes.
Be verycarefulofhotglass.Itdoesn'tlook hotand it cools very slowly.
Treatburnsat once withsodiumbicarbonatesolution.Neverputhotglassware
downon anunprotectedtable.
Whenheatingchemicals or chemicalsolutionsin a test tube, do notpoint
theopenendtowardyourselforanyoneelse. Keeprotatingthe test tube con-
stantlywith a gentle circularmotionsothatbubblesformingrapidly in the
bottomofthe testtubewill not force the liquidoutof the tube in adangerous
way.
Before using glasstubing,be surethatbothends are fire-polished (page 21).
Toputthetubethrougha corkorrubberstopper,wet it first.Holdit with a
piece of cloth and insert it gentlyintothe hole byrotatingit while youapply
pressure. Once you havestartedthetubingthrougha stopper,never hold the