Thames & Kosmos Kids First: Crystals, Rocks & Minerals handleiding

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Thames & Kosmos

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Handleiding

WHAT’S HAPPENING

The citric acid-table salt mixture dissolves both of the ores,

which only strong acids are otherwise able to do, and releases

pungent-smelling sulfur gas. In addition, water-soluble iron

compounds are created, which form an intensely blue dye with

the potassium hexacyanoferrate (III), as is characteristic of

iron. Of course, magnetite also contains iron, but it is too hard

to shave pieces off of.

Test for iron and

sulfur

YOU WILL NEED

› Measuring spoon

› Bornite

› Pyrite

› Citric acid

› Potassium hexacyanoferrate (III)

› 2 Small measuring cups

› Table salt

› Tealight candle

› Distilled water

› Penknife

› Fireproof surface (e.g., an old saucer)

HERE’S HOW

1. In a small measuring cup, dissolve one

spoonful of potassium hexacyanoferrate

(III) in 10 ml of water. Fill half of the other

measuring cup with water.

2. With an adult’s help, use the knife to scratch

off a few little chunks of bornite, and place

them in the large scoop of the double

measuring spoon.

3. Add a few grains of citric acid and table

salt, and carefully heat this for a few

seconds over a tealight candle flame.

During the experiment, leave a window

open to ventilate the room.

4. The citric acid will melt, and you will get a

dark, bubbling mass with vapor bubbles

escaping from it. Heat this melted mass

another 15 seconds. The strange smell that

you perceive comes from the sulfur gases

released from the bornite.

After heating it for a few seconds, dunk the

melted mass into the measuring cup with

water, where it will dissolve. Use the pipette

to drip a little potassium hexacyanoferrate

(III) solution into it. The liquid will turn blue.

6. Repeat the experiment with small chunks of

pyrite.

1 2

4 5

10 ml

Seconds

Leave a window open

to ventilate the room!

Do not inhale the gas!

For citric acid, note the

information about

hazardous substances

on page 6.

EXPERIMENT 14

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