Alster337
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Clean perchloric acid without distillation
Hello,
I'm doing an investigation of several explosive compounds for my A2 chemistry project and I just need some conformation on something before I submit
my project proposal (which obviously needs to be solid if it is to be approved).
One of the types of explosives I would be investigating would be perchlorates. Due to the danger of such compounds compared to say PETN, I have only
decided upon two that can be done safely. One is Hydrazine perchlorate, and the other is methylamine perchlorate.
Im having some trouble with the methylamine perchlorate. I can synthesis the methylamine no problem, but the perchloric acid would have to be produced
in school really, and I know that sodium perchlorate solution combined with HCl forms perchloric acid and sodium chloride. But distilling the acid to
purify it is not really feasible, so I thought that perhaps silver perchlorate would be a better choice since silver chloride is insoluble and could
be filtered off (The silver perchlorate could be produced by the reaction of silver sulphate and barium perchlorate).
Any replies on the feasibility of this method would be appreciated.
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hyfalcon
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Potassium salts have a better solubility curve for separating with fractional crystallization.
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bfesser
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Thread Moved
17-10-2013 at 10:33 |
Alster337
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If im understanding you correctly, using potassium perchlorate isn't feasible as it is not very soluble in water, and im likely to be preparing the
perchlorate solution no more than 40 ml or so.
Simply cooling down the solution of a chloride & perchloric acid would precipitate some of the chloride salt if the right one was chosen based on
solubility, but it would still leave the perchloric acid impure.
I'm not sure if the chloride's presence in the perchloric acid would affect the synthesis of methylamine perchlorate, so if anyone could shed some
light on that I would be very grateful.
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testimento
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A saturated sodium perchlorate solution will form perchloric acid when hydrochloric acid is applied, and any residues of chlorates will be released as
chlorine dioxide gas which can be evaporated using safety precautions. Sodium chloride salts can be filtered out using sand or ceramic filters.
Perchloric acid can be safely distilled at 72% azeotrope, but must not be handled in pure form due to spontaneous mass detonations upon contact with
any organic matter.
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woelen
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I would not distill HClO4 at all at atmospheric pressure. You need vacuum equipment for safe distillation of HClO4. The azeotrope has a boiling point
of around 200 C at atmospheric pressure and I would not feel comfortable with 70% HClO4 at that temperature!
If you have access to barium perchlorate, then why first go through the silver salt? Just add dilute H2SO4 to a solution of barium perchlorate and
allow the precipitate of BaSO4 to settle. Try to use as precisely as possible the right stoichiometric amount of H2SO4, but if that is impossible, it
is better to have a slight excess amount of H2SO4 than having excess barium perchlorate.
If you have NaClO4, then prepare a nearly saturated solution of that in warm water and mix with an excess amount of ice cold 35+ % HCl to this (1.5 to
2 times the stoichiometric amount). Pour the solution of NaClO4 in the HCl, while constantly stirring or swirling. Allow the liquid to cool down. This
causes nearly all sodium ions to precipitate as NaCl. What remains is a mix of HCl and HClO4, dissolved in water.
This mix can be boiled for a while, until the temperature of the boiling liquid goes over 135 C to 140 C. So, keep on boiling, until this temperature
is reached. Then stop boiling (you do not want HClO4 to boil away!!). If you do this, then you drive off all HCl and also quite some water. What
remains is fairly concentrated HClO4 (50% or so), good enough for your experiments. HCl and HClO4 do not react with each other under these conditions.
In this way, you can safely obtain HClO4 of acceptable purity without the need to distill it. You need a fume hood, or need to do this outside,
because of the fumes of HCl.
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Alster337
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Using barium perchlorate & sulphuric acid sounds good, and I do have access to it. However I found out today that Barium salts may not be allowed
for use in school, so i would have to either prepare the perchloric acid at home beforehand, or prepare silver perchlorate at home and bring that in
instead.
I prefer the idea of using barium perchlorate so I shall see if they can make an exception, although it isn't much fuss to prepare the perchloric acid
at home instead.
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snooby
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Don't know if this is the right topic, but I think opening a new one is unnecessary..
I have acces to perchloric acid 70%. If I want to make some silver perchlorate with it, can I just put some silvernitrate in an excess of perchloric
acid and evaporate the acid? Decomposing temperature of silverperchlorate is above 400 C and perchlorid acid is 150C so that's not een problem!
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chemrox
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I was wondering if perchloric was difficult to come by? Whereas meam is available in 40% solution or as the HCl. I know people like to make it but
the synth requires better than garage ventilation.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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phlogiston
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I find it odd that they make you perform (what they perceive as) the most dangerous part of your experiment at home, unsupervised and with amateur
equipment (often 'improvised'), and allow the rest to be done at school.
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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