Results:Sodiumchloride,sucrose,andcoppersulfatepass easilythroughthe
filterpaper.Youcan tellthattheymaketruesolutionsbecausethey leave no
residuein the funnel. Thefilteringseparatedouttheparticlesoftalcumand
gardensoil.Theywerenottruesolutions,therefore.Afteraddingpotassium
aluminumsulfateandrefilteringthewaterthatcontainedthem, even the finer
particlesofsoil, which wentthroughthe first time,separatedout.
Manycities use theprocessofaddingpotassiumaluminumsulfateandre-
filtering to clear up slightlymuddywater. Thisprocess,which, as youremember
from page 37, is calledcoagulation,dependson the factthatpotassiumaluminum
sulfatemakesthe fineparticlesofmudclumptogetherto form largerpieces
which do filter out. However,this processcannotremove dissolvedindustrial
wastes. It cannot purify liquid sewage or germ-polluted water either. The
liquidsewagecontainsdissolved impurities, andgerms are too small to be
filteredoutin thisparticularway.WHATHAPPENSWHENYOUMIXDIFFERENTKINDSOFLIQUIDS
Gather these materials:One small canofconcentratedgrapejuice;saladoil;
analcoholsolutionof85 to 90%strength;2 pintjars;2 testtubes;and 3 quart
jarsfitted with covers.
Follow this procedure:Prepareadatasheet with the followingheadings:
Watermixedwith: ResultFill onequartjarhalfwaywith water.MeasureI full testtubeofconcentrated
grapejuice.Add this to thewater.Cover thejarandshakeit veryhard.Record
the result. Allow it tostandfor a fewminutes,andrecordwhetherornotany
changetakes place. Fill the nextquartjarhalfway withwater.MeasureI full
testtubeofsaladoil andaddit to the water.Coverthejarandshakeit.Record
the resultimmediatelyandagainafterallowingit tostandfor 5minutes.Fill
onepintjarwithwaterandtheotherpintjarwithalcohol.Pourbothintothe
4S