JJay
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Preparation of Anhydrous Aluminum Chloride with a Home-built Tube Furnace
Enough high-firing stoneware clay powder was mixed into a slurry and applied to coat a 30 cm cardboard tube and allowed to dry. This process was
repeated until a layer of approximately 2 mm of clay adhered to the outside of the tube. The tube was then dried in an oven at 300 C. Considerable
cracking occurred. Additional clay slurry was applied to seal the cracks, and the tube was air dried and then oven dried again. The cracks were again
sealed and the dryings repeated until no cracks were evident.
The ends of the tube were wrapped with a single winding of steel wire (approx 2.5 cm from each end), and 10 cm steel terminals were fitted to the
windings. 275 cm of 26 gauge nichrome 80 wire was wrapped evenly around the tube and attached to the steel windings. The tube was placed in a box made
with firebrick and the box placed outside. 120v electrical current was passed through the apparatus with the amperage regulated with a triac dimmer,
starting at about 10% power and increasing to 100% over about eight hours. The heating element was held at full power for several hours and then the
tube was allowed to cool overnight.
The following day, considerable cracking was evident. The tube was sealed with clay slurry and the heating step repeated. One of the ends of the tube,
which was not well heated, crumbled considerably, but this was not deemed a serious problem. The stoneware tube was again allowed to cool overnight.
A 1.3m long 20mm ID quartz tube was placed in the apparatus, with approximately 30 cm of the quartz tube protruding on one side. The long side was
fitted with a drying tube, which was connected to an empty flask (for preventing suckback), which was connected to a gassing apparatus, filled with
water.
10 grams of aluminum turnings were placed inside the quartz tube under the heating element, and 100 grams of calcium chloride monohydrate was placed
in a 3-neck flask. The necks were fitted with a stopper, a gas outlet, and an addition funnel containing 30 mL of 95% sulfuric acid. The ground glass
joints were not greased, though in hindsight, that would have been a good idea. The apparatus was connected to the short end of the quartz tube and
the heating element was slowly brought up to full power.
When the temperature inside the stoneware tube read 700 C, the sulfuric acid was allowed to drop onto the calcium chloride over a time period of about
1 hour. After an additional hour, gas generation had ceased. Both ends of the quartz tube were sealed with corks, and the apparatus was allowed to
cool. White, grey, and green powder were evident inside the tube. The powder, which did not resemble aluminum turnings and emitted plumes of noxious
white smoke on contact with air, was scraped into a media bottle.
The final yield was pretty bad, and the product was not pure, but I think I'm getting somewhere.
I just realized that Brauer discussed a very similar method for making aluminum chloride in a tube furnace... he suggested receiving the product
directly into a flask due to problems with the tube clogging. Also, he put the aluminum turnings into a boat.
[Edited on 1-4-2016 by JJay]
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Daffodile
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Nice post dude, I like how you describe making your (disposable?) tube furnace. Are you going to try again/ update?
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JJay
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I did another run. This time I started the HCl generator before the heat and kept the temperature below 650 C so the aluminum wouldn't melt, and I
don't see any grey powder in the tube (it is cooling right now). It isn't easy to get all of the aluminum into the right spot, though, so I'd really
like to use my boats if I can find something to use to grind them down to size.
Update: the reaction did not go to completion this time. There is a considerable amount of unreacted aluminum.
[Edited on 1-4-2016 by JJay]
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blogfast25
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@JJay:
There are several things that aren't clear to me.
1. What happens to the cardboard tube?
2. Do you dry the HCl before leading it into the furnace?
3. At 650 C in the furnace, pure AlCl3 would not condense at all, until it enters the non-heated part of the quartz tube that is sticking
out of the furnace. But you don't seem to be observing that?
Some pics would be great. 
[Edited on 1-4-2016 by blogfast25]
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JJay
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The AlCl3 and grey powder were condensing the non-heated part of the quartz tube.
The cardboard tube was burned to ashes except at the ends, where it was burned to charcoal that was easily removed.
I most definitely observed AlCl3 condensing in the non-heated part of the tube - it is a white powder. I did not observe any grey powder during the
second run, though - I believe that they grey powder is mostly unreacted aluminum. The white powder can be moved around inside the tube by heating it
with a blowtorch; the grey powder cannot. It's hard to really judge how much powder condenses in the tube as it is condensing, though.
I did not dry the HCl before leading it into the furnace... I know people do dry HCl from similar gas generators sometimes, but it's being generated
from room-temperature sulfuric acid and calcium chloride, so how much water can be in it, really?
I've been using a 2x molar excess of HCl (assuming that the H2SO4 / CaCl2 reaction goes to completion)... I think it may be better to use more.
I have some pics, but I want to do a run where all of the aluminum is converted to AlCl3 before I post any.
[Edited on 1-4-2016 by JJay]
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Loptr
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This has applications in many areas of chemistry, but for AlCl3 I would just heat aluminum powder and anhydrous zinc(II) chloride together in a
container. It takes off ejecting plums of AlCl3 that can be directed into a cold receiving container to collect it.
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JJay
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I've used that method. It works, but it is hard to get good yields, and it is almost as hard to get zinc chloride here as it is aluminum chloride.
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Loptr
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Zinc(II) Chloride, Anhydrous, 10lbs
http://www.hvchemical.com/zinc-chloride-anhydrous-10-lb-tech...
Enjoy!
And I have time if the reagents are cheap. Trading time for money... just another way of doing it.
[Edited on 1-4-2016 by Loptr]
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JJay
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That's a good website, but it simply isn't practical for me to buy zinc chloride from them for making aluminum chloride. It's a hazardous substance,
and shipping it is just as expensive as shipping aluminum chloride. It's not exactly easy to produce large amounts of aluminum chloride that way,
either. I would much rather be able to produce limitless quantities of aluminum chloride using easily obtained chemicals like sulfuric acid, aluminum,
and calcium chloride.
I currently possess a little less than a kilogram of zinc chloride, but I'd really just prefer not to make lab quantities of aluminum chloride that
way.
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