barquentine

My final experiment for the 9th grade this morning in the elemental synthesis set involved me making some chlorine (to demonstrate synthesis of NaCl using pure sodium metal; magnesium chloride, etc.)

I was too busy to have much time to prepare so, remembering that mixing glass cleaning products (ammonia) with household bleach, I borrowed some bleach from home. Using a dropper funnel and filter flask with a bubbler and some 250mL Ehrlenmeyer flasks to collect it, I began ... and it was pathetic. I ended up using about 100 mL of bleach in the reaction flask and added around 100 mL of 30% ammonia solution. I got a grand total of 1 flask of chlorine, about 250 mL. Doesn't seem like a good method so now I am considering all those dire warnings about mixing household chemicals might be O.T.T.

Having only one test flask I set light to the magnesium ribbon and dropped it into the chlorine. Nice bright white-ish yellow-green flame. I am deffo going to have to build a fume cupboard for the lab though ... cough cough

..I've tried the talking-in-a-helium-voice thing, so I thought would it be possible to do the same with hydrogen, or ... no that sounds like a stupid idea, there would be a risk of your lungs exploding like an extra on the set of an Arnold Schwarzeneger SF movie.

Actually I think I will see if the school will pay to get my miniature oxy-acetylene set refilled. I have a small trolley welding set, the acetylene is like a small propane bottle and the oxy looks like a miniature of the full size one, about 2 ft tall. Hmm, way to definitely decompose that KNO3. The stuff melted and that's about 330C but it wouldn't decompose (400C) so I deduce that the hot part of my bunsen burner flame probably is around 360 - 370C. Cool, real cool.

Or maybe electrolysis will make enough ... I guess I could produce some in advance. I have an old computer psu at home, I could use for a supply, plus carbon electrodes. I'll try it. At least it will have the benefit of making H2 as well, since next after O2 I usually have fun making hydrogen. I'm lucky to have a well-equipped lab.

I ran an experiment this morning with my 9th grade students, to demonstrate the properties of oxygen. Of course first I had to show them how to make oxygen so I decided to use two methods:

1. H2O2 + MnO2. This worked OK and I quickly generated a litre of oxygen and filled a large Ehrlenmeyer flask. I did the glowing splint and magnesium ribbon demos.

Then I wanted to dem sodium metal in oxygen. I had used an awful lot of 3% hydrogen peroxide to generate the first litre and recalled that decomposition of KNO3 to KNO2 produces oxygen so I set up a distillation flask and began blasting it with a bunsen burner. No go!

Even with the burner flame playing directly on the glass all that happened was that the potassium nitrate melted but after 10 minutes - no oxygen. It would NOT decompose.

My question, how bloody hot does it have to get? After my trial I do not believe this is a viable method of generating oxygen in the lab, (before you mention it, no I don't have any potassium chlorate in the cupboard right now.)

Thanks

P.S. a chip of Na did not spontaneously ignite in pure oxygen; I had to trigger it by dropping burning Mg ribbon on to it, then it burned bright yellow.