Nitrate reduction using Molten Lead
The means by which I synthesis my nitrites is thru the reduction potential of lead on Sodium Nitrates. This is a faily streight forward reaction that involves melting the metallic Lead in a crucible and slowly adding the nitrate to be reduced. The reaction progresses forward in the manner of,(l)Pb + NaNO3 --> PbO + NaNO2
A useful byproduct of the reaction is litharge and can be a good indicator as to the progress of the reaction. This takes varying amounts of time but nothing to involved although the use of elemental lead is a bit trouble some to me as many nitrites go into the synthesis of consumble substances.
Once the reaction is completed your crucible will be left with a mixture of PbO and nitrite and will need to be seperated but this is no real chore in that PbO is not water soluble so simply add some H2O to the crucible(tin can if your cheep
) and allow it to soak until the cake can be broken up with ease. Add enough H2O to dissolve the Nitrite avalible and grind the mixture to make sure you have dissolved all the nitrite. Decant and filter the solution because PbO is a bitch so you want to make sure all of it has settled before attempting to filter it. Once again add a bit of H2O to make sure all of your nitrite is out and repeat the filter steps.Combine the filtrates and once again filter to the best of your abilitys this time with some cotton or paper towel in the funnel stem to remove all traces you can of PbO from the product and then slowly evaporate the nitrite solution on a low heat to prevent oxidation of the nitrite back to the nitrate.
Now since I am a stickler for making the best of my chemicals you will also want to retrieve that PbO thats in there for what ever use you may find for it.
The PbO is mixed in with unoxidised lead also so simply bottling it up is not an option if you want it pure. No matter though because Pb is a very heavy metal and even though PbO is heavier the PbO is in the form of very finely divided powder. Add water to the ground up mix and stir allowing a second or two for the Pb to settle and then decant the suspension. This will settle to a layer of relativly pure PbO and you will be able to once again decant the water and dry your Pb free PbO. Repeat this as much as needed to remove all the PbO but it should only take two maybe three times before 90% or so of the PbO has been seperated. If you where stirring your nitrate Pb mix the Pb at the bottom will also now be in the form of little lead shot that can be used in the next process but the yeilds are a bit lower from the looks of it.
Nitrites thru ball milling
This is another method I have hands on with and while it showed promise I have not persued it to its full potential yet because it showed a marked decrease in yeilds.
I mixed 2x molar excess of Pb to the nitrates and added a bit of sand to help expose the clean surface of the Lead whilst it was being milled. A very small amount of H2O just enough to make a slush was added and this was allowed to run for two days after adding some steal ball bearings to the mix to aid in exposing fresh metal to the action of the nitrite. Work up was repeated as per the above process except this time the PbO was recoved using GAA to convert the Pb to Lead acetate and filtered from the sand.
Electrochemical Reduction of nitrates
Now this I have not tryed yet but you can bet im going to get on it sometime real soon because the products are Nitrite and Nitric acid so what could be better then have some nitric acid to synthesis hydroxylamine in the cell after your done reducing your nitrites. I don't fully understand whats going on yet but when I do I will let you know how it goes.Quote
THE PRODUCTION OF NITRITE FROM NITRATE.The reduction of nitrate to nitrite can be accomplished satisfactorily, and the process is the subject of a recent patent.1 It has been shown (Miiller and "Weber)2 that in a divided cell, smooth platinum or copper cathodes reduce nitrate to nitrite and ammonia, but platinised platinum gives much ammonia and little nitrite. A spongy copper or silver cathode was found to give the best results. With a current density of 0*25 amps, per dm.3 and a concentration of 2*3 grams of sodium nitrate per litre, a current efficiency of 90 per cent, was obtained. The current efficiency with an amalgamated copper cathode was found to diminish when 50 per cent, of the nitrate had been changed.
Considerable care is evidently needed to prevent the formation of ammonia, since it has been shown by W. H. Easton3 that nitrates may be quantitatively reduced to ammonia by electrolysis. In the patent referred to above, the cell described is suitable for the electrolysis of alkali chloride and is of the bell type, but it is particularly suitable for electrolysing alkali nitrate.
Pure nitric acid is formed at the anode inside the bell and is removed by distillation, which is effected by working under reduced pressure and by heating the bells with superheated steam. The nitrite which is formed at the cathode is drawn off continuously and separated outside the cell. The cell itself acts as cathode, and the anode is of such size as to almost fill the bell and thus reduce the working space of the electrolyte. High current density (16 amps, per dm.2), reduced pressure and high temperature, are favourable to the distillation of a large amount of concentrated nitric acid
This seems very food safe and two for the price of one deal don't sound to shabby at all.
Conclusion: The molten Pb reduction is by far the highest yeilding form I have seen yet but there are many other methods of reducing the nitrates but I have no first hand experiance with them. I will post there reactions later on if no one can step up giving first hand information but I would prefer to see some data from someone that has performed other means of reduction.
