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DubaiAmateurRocketry
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I uploaded the report the Russian team posted that i bought, its in the comment before 
[Edited on 21-6-2013 by DubaiAmateurRocketry]
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caterpillar
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Quote: Originally posted by woelen  | Anything above 75% is dangerous to have around. It is really remarkable to see how much the properties of perchloric acid change with increasing
concentration. At 70% it is actually amazingly inert and not even capable of oxidizing fairly strongly reducing stuff like Na2SO3 or KI, while
anhydrous acid explodes on contact with nearly any reductor (e.g. dust, people, animals, plants  ).
[Edited on 18-6-13 by woelen] |
My dad was a chemist. He studied reactions like Fe++ -> Fe+++, Cu+ -> Cu++ and so on. Once a girl in his lab put some iron powder into HClO4,
wanting to prepare Fe(ClO4)2. I do not know, which concentration this acid has- surely not above 70%, but explosion occurred just when this girl
arrived to my dad to report that all is correct and reaction is going well...
Women are more perilous sometimes, than any hi explosive.
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DubaiAmateurRocketry
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| Quote: Originally posted by caterpillar | | Quote: Originally posted by woelen | Anything above 75% is dangerous to have around. It is really remarkable to see how much the properties of perchloric acid change with increasing
concentration. At 70% it is actually amazingly inert and not even capable of oxidizing fairly strongly reducing stuff like Na2SO3 or KI, while
anhydrous acid explodes on contact with nearly any reductor (e.g. dust, people, animals, plants ).
[Edited on 18-6-13 by woelen] |
My dad was a chemist. He studied reactions like Fe++ -> Fe+++, Cu+ -> Cu++ and so on. Once a girl in his lab put some iron powder into HClO4,
wanting to prepare Fe(ClO4)2. I do not know, which concentration this acid has- surely not above 70%, but explosion occurred just when this girl
arrived to my dad to report that all is correct and reaction is going well... |
Some perchlorates react with water.
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woelen
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Even with plain acids like 30% HCl you can get very violent reactions (nearly explosive), especially if the amounts are scaled up. You need to provide
more info about the experiment, especially the scale at which it was performed.
I do not believe that adding a small spatula full of iron powder, added to e.g. 60% HClO4 will lead to an explosion. If, however, a tablespoon full of
iron is added to e.g. 50 ml of 50% HClO4, then I can imagine that the reaction at first starts gently, but slowly it becomes more and more violent and
finally you get a severe runaway. If you want an idea of what can happen, add some coarse granules of Al to 30% HCl. At first nothing happens, but
after a few minutes the reaction becomes extremely violent. Only use test tube quantities for this experiment!
Here, simple acidity does the job already, I'm not talking about strongly oxidizing anion-reactions.
What I wanted to say with my previous post is that HClO4 is amazingly inert besides its acidity when the concentration remains below appr. 70%. It
just reacts like a strong acid and not like a strong oxidizer such as HNO3 at similar concentration.
@DubaiAmateurRocketry: The fact that some perchlorates react with water does not mean anything in this context. These perchlorates would not even be
formed under the conditions, discussed here. What you mean is that some metal salts easily are hydrolysed. This is not unique to perchlorate, it is
unique to the metal-ion. Ti(ClO4)4 certainly cannot exist in water, it reacts to hydrous TiO2 and HClO4. But a similar thing is true for any Ti(IV)
compound. E.g. TiCl4 reacts violently with water to form TiO2 and HCl and Ti(NO3)4 reacts to TiO2 and HNO3. There are many metal ions which show this
behavior. Some of these ions hydrolyse completely in neutral solution (e.g. Ti(4+), Zr(4+), Sn(4+), Sb(3+), Bi(3+), Mn(3+)), others hydrolyse partly
(e.g. Fe(3+), Al(3+), Cr(3+), Ce(4+), Sn(2+), Pb(2+)).
[Edited on 21-6-13 by woelen]
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caterpillar
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Unfortunately, I cannot add details above what I already told. My dad is dead and therefore I have no way to ask him, what really happened. One wise
boy wanted to get dry (CH3)3PO4- ordinary trimetilphosfate, but he used Mg(ClO4)2. In this case at least it is clear, why this mixture exploded.
Women are more perilous sometimes, than any hi explosive.
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AndersHoveland
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| Quote: Originally posted by caterpillar | | My dad was a chemist. He studied reactions like Fe++ -> Fe+++, Cu+ -> Cu++ and so on. Once a girl in his lab put some iron powder into HClO4,
wanting to prepare Fe(ClO4)2. I do not know, which concentration this acid has- surely not above 70%, but explosion occurred just when this girl
arrived to my dad to report that all is correct and reaction is going well... |
I think this probably had to do with the perchlorate not being very stable in the presence of Fe+2 ions while the concentrated solution was being
heated. Once the activation energy was overcome, the Fe+2 was oxidized. So this particular problem would probably not be an issue with other salts.
Although added caution never hurts.
With Ti(ClO4)4 hydrolyzing in water, I am not sure what the maximum concentration of perchloric acid that can result, but I suspect pure anhydrous
HClO4 is not obtainable. Or in other words, that the hydrolysis is not completely stoichiometric. And similarly, I also doubt Ti(ClO4)4 would
hydrolyze in ~90% perchloric acid, though perhaps an especially acidic adduct could form, H2Ti(ClO4)6.
I am sure that dropping a piece of Ti(ClO4)4 into water would be an extremely violent reaction, but whether it could actually explode, I am not sure.
Because it is possible that the concentrated perchloric acid generated on hydrolysis could detonate from the intense heat of hydration. I am not sure
what the minimum concentration is that can detonate (without any other reducing agent present), but from what I have read it seems to be around 85%.
[Edited on 22-6-2013 by AndersHoveland]
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caterpillar
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| Quote: Originally posted by woelen |
What I wanted to say with my previous post is that HClO4 is amazingly inert besides its acidity when the concentration remains below appr. 70%. It
just reacts like a strong acid and not like a strong oxidizer such as HNO3 at similar concentration.
[Edited on 21-6-13 by woelen] |
You are right, talking about COLD HClO4. But hot acid (near its boiling point) is strong oxidizer- and even if reaction starts with cold acid,
temperature may easily go up.
Women are more perilous sometimes, than any hi explosive.
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AndersHoveland
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If we look at other non-oxidizing acids, titanium tends to be very resistant to attack at dilute concentrations, but at higher acid concentrations or
heated, the attack is more rapid. I think if the acid concentration is high enough, TiO2+ begins to dissolve in solution.
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