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THIS
PROCEDURE WILL SYNTHESIZE FERROFLUID.
THIS MAGNETIC LIQUID CAN
DEFY GRAVITY, CHANGE DENSITY, AND CAN FORM SPIKES WHEN NEAR A MAGNET. |
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| WARNINGS:
THIS SYNTHESIS INVOLVES FLAMMABLE SUBSTANCES, TOXIC FUMES, AND
HEAT. WEAR SAFETY GOGGLES, AND PERFORM IN A WELL VENTILATED
AREA. FOLLOW EMERGENCY PROCEDURES MARKED ON EACH OF THE CHEMICALS'
CONTAINERS. BEWARE THAT AMMONIA FUMES ARE TOXIC. |
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DESCRIPTION
FERROFLUIDS
ARE A STABLE (MEANING INSEPARABLE) SUSPENSION OF NANOMETER SIZED SOLID
MAGNETIC PARTICLES IN A CARRIER FLUID. THE PARTICLES ARE COATED
WITH A SURFACTANT; A CHEMICAL WHICH PREVENTS THE PARTICLES FROM CLUMPING
TOGETHER AND FORMING A SOLID MASS. THE MOST COMMON TYPE OF
FERROFLUID, PRESENTED HERE, IS AN OIL BASED FLUID CONSISTING OF
MAGNETITE AS THE MAGNETIC SOLID, AND OLEIC ACID AS THE SURFACTANT.
THE FINAL COMPONENT IS A CARRIER FLUID, WHICH SUSPENDS THE
PARTICLES; IN THIS EXPERIMENT THE CARRIER WILL BE
KEROSENE.
FERROFLUIDS
FIND USE IN HIGH END SPEAKERS, AS WELL AS HIGH PERFORMANCE SHAFT
SEALS. SOME AQUEOUS FORMULATIONS CAN BE USED IN EYE
SURGERY.
OLEIC ACID
IS A FATTY ACID, AND IS HISTORICALLY IMPORTANT FOR IT'S ROLE IN
SOME OF THE FIRST SOAPS. SODIUM OLEATE, A SALT OF OLEIC ACID, IS
STILL WIDELY USED IN SOAPS TODAY. THIS MOLECULE IS INTERESTING
BECAUSE HALF OF IT IS SOLUBLE IN WATER AND HALF IS NOT. THIS MEANS, ESSENTIALLY, THAT ONE END IS 'STICKY' AND ONE IS NOT. THE MOLECULE'S STICKY END CAN ATTACH ITSELF TO A MAGNETITE
PARTICLE AND WHEN THE PARTICLE IS COMPLETELY SURROUNDED, THE ACID
MOLECULES KEEP THE MAGNETITE PARTICLES FROM STICKING TOGETHER. THIS IS THE SAME WAY SOAPS WORK;
DIRT IS COATED AND MADE 'SLIPPERY' SO IT CAN BE WASHED AWAY.
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MATERIALS |
-OLEIC
ACID
-HOUSEHOLD AMMONIA
-PCB ETCHANT (FERRIC CHLORIDE SOLUTION)
-DISTILLED WATER
-STEEL WOOL
-A STRONG MAGNET
-KEROSENE |
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EQUIPMENT
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-HEAT
SOURCE
-2 PYREX BEAKERS (MEASURING CUPS)
-PLASTIC SYRINGE
-COFFEE FILTERS |
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PROCEDURE |
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WHY?
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THE
FIRST PHASE IS TO PRODUCE FERROUS CHLORIDE FROM FERRIC CHLORIDE (PCB
ETCHANT), WHICH WILL LATER BE USED TO PRODUCE MAGNETITE. NOTE THAT
COMMERCIAL PCB FLUID IS 1.5M, SO THE AMOUNTS GIVEN BELOW WILL PRODUCE
ABOUT 5 G OF MAGNETITE.
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1.
WITH
THE PLASTIC SYRINGE, MEASURE 10ML OF FERRIC CHLORIDE (PCB ETCHANT) INTO
A PYREX CUP. ADD
10ML OF DISTILLED WATER. |
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THIS
PORTION OF FeCl3 WILL BE REDUCED TO FeCl2. IT
MUST BE DILUTED FIRST BECAUSE OF SOME ADDITIVE IN RADIOSHACK PCB FLUID
THAT CAUSES SIDE REACTIONS WITH THE IRON.
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2. ADD
A SMALL PIECE OF STEEL WOOL. STIR OR SWIRL THE
SOLUTION UNTIL IT HAS TURNED BRIGHT GREEN. FILTER WITH A COFFEE
FILTER. |
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FeCl2
IS BRIGHT GREEN AFTER FILTERING. EVEN
BEFORE YOU FILTER YOU'LL NOTICE A COLOR CHANGE, BUT THERE WILL BE 'CRUD'
FLOATING IN IT.
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| NOW
MAGNETITE WILL BE PRECIPITATED FROM A SOLUTION OF FERRIC AND FERROUS
CHLORIDE.
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| 3. ADD
20ML OF FERRIC CHLORIDE (PCB ETCHANT) TO THE GREEN FERROUS CHLORIDE
SOLUTION |
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FeCl3 AND FeCl2
REACT IN A 2:1 RATIO. THE CONCENTRATION OF FeCl2 IS HALF THAT OF
FeCl3 (SINCE WE ADDED WATER), SO EQUAL VOLUMES PRODUCE THE REQUIRED
RATIO. |
| 4. WHILE
STIRRING, ADD 150ML OF HOUSEHOLD AMMONIA |
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THE
AMMONIA PARTICIPATES IN A COMPLEX REACTION WITH THE IRON SALTS TO
PRODUCE MAGNETITE, Fe3O4, WHICH FALLS OUT OF SOLUTION. THE
AMMONIA REACTS WITH THE EXCESS CHLORINE, PRODUCING MAGNETITE POWDER IN
AMMONIUM CHLORIDE SOLUTION. |
| THE
MAGNETITE WILL NOW BE COATED WITH OLEIC ACID.
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| 5.
IN
A WELL VENTILATED AREA, HEAT THE SOLUTION TO NEAR BOILING.
ADD
5ML OF OLEIC ACID, WITH STIRRING. CONTINUE
TO HEAT NEAR BOILING UNTIL THE SMELL OF AMMONIA DISAPPEARS, USUALLY
ABOUT AN HOUR. |
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THE
OLEIC ACID REACTS WITH THE AMMONIA TO FORM AMMONIUM OLEATE, A SLIGHTLY
SOLUBLE SOAP. THE HEAT CAUSES THE AMMONIUM OLEATE TO BREAK DOWN,
AND THE OLEATE ION ENTERS SOLUTION WHILE THE AMMONIA ESCAPES AS A
GAS. THE OLEATE ION
ATTACHES TO A MAGNETITE PARTICLE, AND IS RECONVERTED TO OLEIC ACID. |
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COATED MAGNETITE WILL NOW BE SUSPENDED IN A CARRIER FLUID.
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| 6. IN A WELL
VENTILATED AREA, ADD 100ML OF KEROSENE TO THE COOLED SOLUTION.
STIR UNTIL MUCH THE BLACK COLOR HAS LEFT THE WATER AND TRANSFERRED TO
THE KEROSENE |
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WHILE
BOTH MAGNETITE AND OLEIC ACID ARE INSOLUBLE IN WATER, OLEIC ACID IS
SOLUBLE IN KEROSENE. STIRRING
ALLOWS THE OLEIC ACID COATED PARTICLES TO LEAVE THE AQUEOUS PHASE AND
ENTER THE KEROSENE |
| 7. POUR
OFF AND COLLECT THE KEROSENE LAYER. DISCARD
THE WATER. VOILA! |
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THE
KEROSENE HAS SUSPENDED THE MAGNETIC PARTICLES, AND IS NOW A FERROFLUID. |
