[Donaldson Tan]

the idea of using nitrogen to drive the car is purely for environmental sake. try to minimise presence of oxygen and heat, to prevent production of toxic oxides of nitrogen

[Demotivator]

nitrogen and oxygen won't react without a lot of heat, like in a high compression combustion engine. That isn't the case here as the gas is vented.

[Donaldson Tan]

I tend to think a large scale reaction will produce lotsa heat, to provide sufficient power to drive a car..

[movies]

I think the real question is how much gas will be produced.  That's what will be driving the car, right?  You might be able to do this on relatively small scale and therefore avoid problems with heat.

[Donaldson Tan]

nitrogen and oxygen won't react without a lot of heat, like in a high compression combustion engine. That isn't the case here as the gas is vented.

I tend to think a large scale reaction will produce lotsa heat, to provide sufficient power to drive a car..

I had meant that if this reaction were to carry out on large scale, more than sufficient heat would be produced to cause nitrogen to react with oxygen to produce oxides of nitrogen. Nevertheless, the risk for this isn't that warranted (in my opinion). Just install a catalytic converter to convert the oxides of nitrogen to harmless gases at the exhuast. Moreover the heat produced can be used to power electronic devices, as it's the rapid expansion of gas that drives the car, not heat.

I think the volume of gas (at rtp) produced per unit volume of sodium azide would be a lot partly because azide is a solid. I'm wonder how to store azide inside the engine such that sodium nitride formed can be removed after reaction - note azide and nitride are both solids, not fluids. Perhaps store azide in the form of replaceable racks..

[Limpet Chicken]

I really can't warn strongly enough not to use sodium azide for ANYTHING that doesn't explicitly require its use in the reaction, it inhibits cytochrome oxidase in a similar manner to cyanides, and has roughly the same toxicity of KCN, that, and it is highly explosive, its used in car airbags, along with iron compounds, sillica etc. as the gas source in airbags.

The reason for the other impurities (impurities to those people scrounging NaN3 from car airbags anyway ) is to prevent one of the decomposition products of alkali metal azides, because the group one azides are pretty unstable and detonate from impact or flame into nitrogen, and a cloud of finely dispersed hot alkali metal.



On another note, I once considered controlled thermal decomposition of rubidium/caesium azide as a possible way to prepare the metals, maybe starting by preparing the azide from the alkali carbonate and hydrazoic acid (caution, a toxic volatile acid similar to hydrocyanic acid)
then thermal decomposition of continuous SMALL amounts of the azide, the nitrogen forming an inert atmosphere for collection of the alkali metal.

What chance does this have of succeeding? I think it would work for all alkali metals except lithium, due to its formation of the nitride directly from combination.

[jdurg]

It stands almost no chance of succeeding.  The little bits of oxygen and moisture in the air would cause the metals to catch fire almost immediately, and if you concealed it in a small area in order to keep the oxygen/water out, the building gas pressure would cause an explosion.  It could be done if you had a dry box with a fully inert argon atmosphere in there, but without a dry box I wouldn't even think about attempting that.  

[Limpet Chicken]

That is what I was thinking of, only using a nitrogen atmosphere or maybe even CO2 instead of argon for availability's sake.

[jdurg]

I believe that they may react with the CO₂ as well, but I'm not 100% sure about that.  The biggest problem is that the metals will be formed as tiny little "blobs" which will increase their surface area and propensity for reacting a tremendous amount.  

[jdurg]

There are also a few other things that you'll need to keep in mind.  One is that both Rubidium and Cesium have an INCREDIBLY strong affinity for oxygen.  That is why they are used as "getters" when a completely oxygen free atmosphere is required.  Couple that with the miniscule particle size of the generated metals and the chances of them surviving is next to nothing.  In order to have an "inert" atmosphere, you will need analytical grade gasses which are incredibly expensive.  We're talking 99.9999% pure gasses here.  The Lab Grade or Technical Grade gasses which are easy to acquire generally have a good deal of oxygen in them, and when in contact with the rubidium or cesium, that oxygen will have a very adverse effect on your metals.  Even if you generated the atmosphere in situ, there will be impurities that will easily react with the very tiny amounts of cesium/rubidium that will be produced.  

In the mass manufacturing of these metals, they generate larger amounts at a time using electrolysis and have a completely inert argon atmosphere over the metals.  A small amount of them are lost due to impurities in the atmosphere, but becuase of the scale of the reaction it is still profitable.  When trying to do what you would like to do and generate the metals on your own, you'll find out that the cost of doing so would be far more than the cost of just purchasing the metals from various dealers online.

[movies]

The dry box in our lab has a catalyst for decomposing oxygen.  Is that a Rb/Cs thing like you mentioned jdurg?

Does anyone know?

[deciple77]

Ok, there is a new twist in my project, I just recived some of the specifications for the project.  The chemical reaction must be in a closed system, abloulutly no emmisions whatsoever (even compleatly harmless gasses   ) .  So I guess I am going to incorperate some kind of mechanical device.  Any ideas?

[movies]

Maybe you could still use the gas emmisions to drive the car, but then after whatever turbine you have, attach a balloon to contain the emissions.

Otherwise, you might have to find a reaction that just produces heat and somehow harness that for power.

[jdurg]

The dry box in our lab has a catalyst for decomposing oxygen.  Is that a Rb/Cs thing like you mentioned jdurg?

Does anyone know?

It might be.  However, Barium is also a VERY good oxygen getter and is a teency bit less dangerous than rubidium or cesium, so that may be used in its place.  I do know that in every vacuum tube for televisions and whatnot, there is a small cell of either rubidium or cesium designed to get rid of the miniscule amount of O₂ that might be in there.  (But we're talking VERY miniscule.  The vacuum pumps they use suck out nearly all the gas, and the cesium/rubidium/barium that's used is only there to get rid of the stuff that the vacuum cannot.)

[billnotgatez]

use a chemical process like a battery to drive an electric motor - i gave a lemon example in previous post