Log in

View Full Version : Arsenic from Herbicides


nbk2000
April 26th, 2006, 04:51 AM
Experiments in CW sometimes require precursors which are difficult, if not near-impossible, for the amateur to obtain. One such chemical is arsenic, from which such things as Lewisite and Adamsite can be derived.

Long available in the old days as a rodent poison, it's been restricted for the last century due to homicidial poisonings with it.

Purchases from chemical suppliers entail records, red-flags in government databases, and who-knows-what since 9/11, thus such commercial sources are to be shunned as leperous whores.

Fortunately, arsenic-based chemicals are still available at most hardware stores in the form of defoliants intended for sheeple to use on their driveways and such in pursuit of a greener pasture than the neighbors. :rolleyes:

I'll not be naming the exact brands (anti-k3wL), but they are quite common in the US, and arouse no suspicion in their purchase, being available in such places as ACE, Lowes, Home Depot, etc.

The 2 chemicals most often used are listed below:


Monosodium methyl arsenate, CAS#2163-80-6, CH4AsNaO3, MW 162
Cacodylic acid, CAS#75-60-5, C2H7AsO2, MW 138

The arsenic content of both of these chemicals is about 50%.

So, out of a pint of defoliant, you can expect to get almost six ounces of arsenic, for only $8. :)

But getting the arsenic out of them is a process that needs to be developed.

The MSDS's for these products mentions that acidic conditions in the presence of reducing metals, such as aluminum or zinc, will produce arsine gas.

Arsine, a very poisonous gas in itself, is oxidized to arsenic trioxide when the gas is burned in air, the oxide forming a white smoke that can be collected on a cold surface held above the flame.

Another option would be to pass the arsine gas through an alkali solution, such as sodium hydroxide, and collection the resulting arsenide salt.

The most direct route is to pass the arsine gas through a solution of silver nitrate, whereupon the nitrate is reduced, the hydrogen removed, and arsenic trioxide remains in solution to be collected by evaporation.

But this requires a fairly expensive reagent which, even though it can be regenerated by cheap nitric acid, would be prohibitivly expensive for quantitiy production.

All these processes involve the creation of a highly toxic gas, which it would be nice to avoid having to use, if an alternate process could be found that would require simple mixing of reagents with the herbicide to produce the desired arsenic salt as a preciptiate.

nbk2000
March 2nd, 2007, 04:57 PM
Bingo! :D

US5545800 - Clean process to destroy arsenic-containing organic compounds with recovery of arsenic.

MSMA, in oil or ether, is reacted with Fe/H2SO4 or Al/HCl, to produce arsine which is bubbled into permanganate solution to form arsenic (tri)oxide.

TreverSlyFox
March 3rd, 2007, 04:55 AM
Hmmm, lets see if I have this right. It is possible to create Arsine Gas by adding aluminum or zinc to either of these OTC herbicides?

If that is the case then these are weapons in and of themselves. Such as adding the required metal and placing the open container in front of an air intake to a building or other enclosed space.

Is my thinking correct and would it be just that easy?

kurtz
March 3rd, 2007, 07:28 AM
The ease of this conversion - the strenuousness of the conditions necessary for using the more commonly available reductants on this particular substrate, can only be determined by experiment. There is nothing in the patent that actually suggests that it is easy for amateurs with commonly available items.

The patent merely tries to claim everything, without facts. Reduction of AsCl3 with sodium to supposedly obtain sodium arsenide (no yield of anything is specified anywhere) seems distant to methanearsonic acid and its salts. I'm unaware of any solvent for methanearsonic acid that wouldn't react with sodium, otherwise that could be tried for hahas.

I could not get this patent from espacenet or google, only uspto.

nbk2000
March 3rd, 2007, 10:55 AM
The MSDS for MSMA (http://www.pbigordon.com/pdfs/MSMAHerbicide-MSDS.pdf) says:

MSMA, in the presence of many metals, can react with nascent hydrogen to form arsine gas.

Physical Properties (http://www.inchem.org/documents/hsg/hsg/hsg69.htm):

Disodium Methanearsonic acid
MP 132-139C
Very soluble in water (1000g/L), methanol; insoluble in organic solvents

Monosodium Methanearsonic acid
MP 115-119C
Soluble in water (570g/L), methanol; insoluble in organic solvents


More detailed information on physical properties of various arsenic-derivatives:
http://www.atsdr.cdc.gov/toxprofiles/tp2-c4.pdf

Since MSMA is soluble in water and methanol, and pretty much nothing else commonly used in OTC products, it seems likely that you can simply boil off (outside!) the excess solvent and recover the solid MSMA.

Then, dissolve it in minimal water, add in aluminum foil or iron powder, and add an acid, either sulphuric or hydrochloric, to generate the arsine.

Pass the arsine gas through a hot tube to reduce to metallic arsenic, or burn to produce As2O3.

Arsine can itself be used as a toxic gas, the OSHA IDLH threshold being 0.02mg/L.


Because it is nonirritating, persons exposed to dangerous levels may experience no immediate symptoms.
...
Odor is not an adequate indicator of arsine's presence and does not provide reliable warning of dangerous concentrations. Serious exposure can occur even if the garlic-like odor is not smelled. Arsine is heavier than air and may cause asphyxiation in enclosed, poorly ventilated, or low-lying areas.


Source (http://www.mednets.com/index.cfm/fuseaction/articles_arsine_arsenic_poisoning_and_exposure_tox icology-Arsine)

megalomania
March 4th, 2007, 01:23 PM
That actually sounds like an analytical procedure to determine total arsenic content. I don't keep up much with evil anal chem, but I absorb a few details now and again in my travels.

nbk2000
March 4th, 2007, 02:47 PM
Actually, it is.

I read in Saxons Granddad's Wonderful Book of Chemistry, in the Medical Jurisprudence book, described as the 'Marsh' test.

Further searching finds a video demo:

http://www.cci.ethz.ch/experiments/Marsh/en/stat.html

kurtz
March 5th, 2007, 03:47 AM
Yes, but again, that is inorganic arsenic. Reduction of methanearsonic acid with Zn or Mg + aq. HCl, Zn amalgam, or (best) acidic borohydride will only produce methylarsine, not arsine. There are many examples of this in the analytical literature, specifically done on MAA, and also DMAA (giving dimethylarsine of course).

Now, one might be able to oxidize the methyl of the MSMA with permanganate or whatever and then reduce, or leave it the way it is; or oxidize the methylarsine in a safer and more convenient way than burning it; or heat the acid to first get the pyro acid and water vapor, then arsenic trioxide vapor and some organic vapor.

Captain Obvious would say that arsenic vapor is best avoided, if he was here.

I've seen an unreferenced comment that conc. sulfuric acid, (probably hot as well) reacts with MAA to give among other things arsenic trioxide and CO2. Another one of those experiment for the truth things.

nbk2000
March 5th, 2007, 06:28 AM
Would not the methylarsine burn to form the trioxide smoke? Which is the whole point of the reduction anyways, as the smoke can be condensed and the oxide used for synthesis.

kurtz
March 5th, 2007, 08:42 AM
Yes, and it might just be spontaneously flammable. It just sounds unattractive to me compared to alternatives, at least on a small scale. But that is something that could probably be most neatly scaled up quite large.

nbk2000
March 5th, 2007, 08:45 AM
What alternative means is there?

Bugger
March 6th, 2007, 05:47 AM
What about lead arsenate, Pb3(AsO4)2 ? It was formerly used as an insecticide to spray on fruit like apples and tomatos to stop caterpillars from eating into them, but it has been largely discontinued because the stuff has to be washed or wiped off before the fruit can be eaten. There are likely to be old bags of it left lying around in sheds.

kurtz
March 26th, 2007, 08:56 AM
You know how heating sodium acetate with NaOH gives methane and carbonate? Compt. rend. 146, 1280 (1908) mentions that heating DSMA with excess NaOH at 250-280C gives a quantitative yield of trisodium arsenate like so: CH3AsO3Na2 + NaOH -> CH4 + Na3AsO4. It goes on to say that heating sodium cacodylate to 180C with NaOH gives DSMA and methane, and of course further heating to 280C removes the second carbon.

It would follow that if one has the free acids or MSMA, it is just a matter of adding more NaOH. If you want arsine itself instead of methylarsine or dimethylarsine, now you can get it with the acid+metals-that-dissolve-in-acids-releasing-hydrogen mentioned above.

nbk2000
September 16th, 2007, 09:54 PM
It seems another OTC source of arsenic maybe Ironite fertilizer:

http://www.envirolaw.org/cases/poisonbg.html

Analysis showed Arsenic at 4380 ppm.

There are, however, a lot of other metals mixed in, such as cadmium, cobalt, copper, mercury, molybdenum, nickel and selenium. But, since a lot of these are toxic too, seperation may not be required.