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12AX7
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It'll probably burn like a flare. The last charge of CuO/MgAl I burned produced gaseous products, so everything in the path of the gas got
metallized pink, even organics 
Tim
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kine
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Ok i made some but i have no scale (my food scale has broken) so i added by volume. The copper suflate is anydrous so i have used the same volumetric
quantities of KOH and CuSO4. Due to exesive head from the moisturised caustic potassium the reaction gave instantly CuO without any heating so right
now i have a black colored powder at the botom of the solution. should i let it stay all day for the reaction to complete? Or should i put it in the
sun to vaporise and then wash it in a cloth to remove any potassium suflate?
What is the exact weight ratio when using KOH
Sorry for the ton of questions but i just learning, thanks for the info.
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kine
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I found cromium oxide 1 kg for 7 euro (around the same as US dolars) Is it safe for thermite/flash compositions? It is the green oxide.
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neutrino
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It should already by done by now. I suggest adding excess copper sulfate because strong base solutions are nasty to work with. Just keep adding
CuSO<sub>4</sub> until you get a blue color in the solution. Then filter, wash, and dry.
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kine
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Well i got a good yeld in a big plastic plate and waiting water to vaporise with a 500w heat lamp above.
After all (if it works with thermite) it is cheaper to make CuO with this way. Still i haven't found a pottery to sell me CuO, only stores that
sell pottery stuf.
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12AX7
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Chromium thermite works just fine, yielding metal globules as with iron oxide. It ought to be cooler (since chromium is more reactive than iron), I
don't remember if it needs some sulfur to speed it up.
Tim
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The_Davster
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Kine, you may want to boil it for a few min, 10 to 15 should be good, in order to ensure that you just have CuO, and no Cu(OH)2 trapped inside.
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kine
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Can't that be done with the dry powder in the pyrex? The impurity Cu(OH)2 will not react with the pyrex so with the heat (dry powder) it will
convert to CuO.
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The_Davster
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Compared to CuO made from Cu(OH)2 roased, CuO made by boiling Cu(OH)2 seems to work faster in a thermite. I got this by comparing Chemoleo's
results and mine.
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kine
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Ok i will boil it down but how can i filter it? The vaporising pan seems bad idea for me because it will hold upon evaporation CuSO4 salts and K2SO4
salts in the CuO.
So i will do this:
Put the CuSO4 in the pyrex with water dissolve and in another glass vessel i put some KOH with water to dissolve. Then i pour the KOH solution in the
pyrex and heat to boiling point (is it completly safe indoors?).
After 10-15 min CuO has formed but there are also some suflate salts in the solution. How do i remove those impurities? After boiling the water out
rewash it with hot water again and again?
| Quote: | Compared to CuO made from Cu(OH)2 roased, CuO made by boiling Cu(OH)2 seems to work faster in a thermite. I got this by comparing Chemoleo's
results and mine.
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Any idea why his hapens?
[Edited on 12-8-2005 by kine]
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The_Davster
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Well for the CuO that I made for use in thermite; I added solid NaOH to a concentrated solution of CuSO4 that was nearly boiling, pretty much just
CuO precipitates from the heat of the solution as well as from the exotherm of the NaOH dissolving. There was still some Cu(OH)2 there so I boiled
for around 5-10 min after which time all the precipitate was black with no traces of blue and settled to the bottom of the beaker rather fast. I just
directly filtered it from there and washed the CuO with lots of dH2O. One batch I did I did not wash it enough so when the CuO dried there was
noticeable sodium sulfate crystals on the CuO, this however did not affect the preformance of the CuO in thermite to any noticeable degree. An
ethanol or methanol wash of the CuO would help remove any sodium sulfate held in there by capillary action, but I have not botherd with this, just
washing well with lots of distilled water. Just air dry till dry and then 5-10 min on a hotplate to get rid of residual moisture and it is done.
Also be sure with all steps involving heating make sure to use boiling stones and constant stirring and add the NaOH slowly. If the NaOH is added too
fast to a boiling CuSO4 solution the contents of the beaker have the nasty habit of jumping out at you. As is the problem with all reactions involving so much precipitate. A good way to prevent this is to keep everything
just below boiling while adding the NaOH and then raise the temperature with constant fast stirring and boiling stones while boiling the CuO to rid
the remaining Cu(OH)2.
EDIT...sorry for double post, I could not edit and attach a pic.
[Edited on 12-8-2005 by rogue chemist]
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The_Davster
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Here is a pic of what happens when solid NaOH is added to boiling(or possibly superheated) CuSO4 with no boiling stones and insufficient stirring.
As for why this method for CuO makes a superior thermite...I don't really know(but I do have some speculation). Chemoleo and I had discussed
this a bit in the exotic thermites thread(or was it the electrolytic production of CuO thread?). Possibly roasting the CuO on too high of heat
decomposes some CuO, or perhaps in aqueous solution the CuO is less dense or more porous allowing more contact with the Al powder.
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kine
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Ok everything is perfect (i got a lot of black powder in a pan with lots of water) and i want to filter it because sun evaporation takes too long.
What should i use for filtering without having to scrape it from the filter? Coffe filters maybe?
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neutrino
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Those should do. If the weight of the CuO tears the filters, stack a couple or try a cloth support.
[Edited on 12-8-2005 by neutrino]
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12AX7
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Don't forget to pour off excess liquid, add clean water, wait for it to settle, pour off again, and so forth to remove soluble salt. This is
called decantation.
Tim
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kine
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Ok thanks for the clarification. I have the wased and clean powder on the cloth (found it good since the yeld is good) it is drying under a heat lamp.
When it is ready i will give a small test on CuO/Al. Does the adition of sulfur give any lower ingnition temerature? I already got some S/Al mix for
ingnition. Is it safe to ingnite a 2gram thermite with starter S/Al by a match?
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praseodym
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I think the addition of sulphur does make reaction more vigorous but wouldnt the burning of sulphur produce sulphur dioxide gas which is something you
dont really want to smell? Starting the thermit with a match shouldnt be a problem as long as a fuse is used. The last time I did a thermit was with a
Bunsen burner and a fuse...
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12AX7
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Actually it makes H2S. 2Al + 3S = Al2S3, in moist air Al2S3 + 6H2O = 3H2S + 2Al(OH)3 (or whichever hydroxide forms in these conditions).
Tim
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kine
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H2S is explosive on open air at the right concentrations and a little toxic.
Ayway tomorow i will give a test because it is late now.
The powder needs to be crushed in a mortar, mine is a metal one made from a soft metal, must be lead. Is it ok to crush it in that or it will react
with the lead?
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12AX7
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Just fine. A little reaction might happen on the contact surface (comparable to mashing Hg2S in an Ag mortar making Hg globules... what was that
process called?!) but PbO isn't a problem.
Tim
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kine
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I have film canister half full with CuO/Al (how many gram is this?)stored with the lid on a shelf, unluckily it is too windy outside to test it. Maybe
i should use it with the canister or try another calm day.
I had somwhere some barium nitrate sparklers but i can find them and instead of those i made a comon sucroze potssium nitrate fuses in thin straw will
this ingnite the S/Al?
Also does S/Al work without air oxygen? S suposed to work as the oxidiser.
Edit: Hope that all those combos are safe on my shelf....
[Edited on 14-8-2005 by kine]
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12AX7
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I would guess... 30 grams?
Yes to everything else.
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The_Davster
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Don't you know how much CuO and Al you mixed? Or did you not make the mix stoichiometric and just mixed a bit of each together?
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kine
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Used equal volumetric amounts and added a little extra CuO, i remember reading someone did this way because he had no scale too. I will buy a new food
scale soon since it is very important in such compositions.
I made another big amount (must be around 500grams) CuO and it is drying now. I have to note that it is far more cheaper than buying CuO. If i
remember well it is 5$ per pound in US. i can buy CuSO4 4kilos for 3 euro and 3 kilos KOH for 2euro. Thats 5euro for a huge amount, something like
2kilograms CuO and more...
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neutrino
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Food scale? You really need something better. See this thread.
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