Alexander

....even though fashioning something into a firework probably definately constitutes 'practical use'.

I would also observe that the 100g limit does not allow us to make fireworks, so it's abolition would not actually change anything.

I have been trying to find a thread or explanation on this, it doesn't help that 'hse' is too short to be an allowed search term

The exemption is fashioned in such a way that includes the creation of a complete firework, arguing that 'practical' should be interpreted in such a way as to invalidate the primary legislation does not sound enforceable to me. I cannot find any official guidence on the exemption in the Approved Code of Practice either.

Could someone point me to something concrete?

Your maths/chemistry looks fine and will not be affected by doing the reaction in solution but it may not be the best way to do it practically. Calcium oxalate is essentially insoluable like calcium carbonate, reacting a solid to produce another solid in this way can be problematic if the new solid coats the particles of the old one preventing contact with the solution.

A better way can be to arrange for everything to be in solution at the start of the reaction and cause the product to precipitate out. For example, if you dissolve solid oxalic acid in potassium carbonate solution to produce neutral potassium oxalate (K2C2O4) which has a solubility of 33g per 100ml at 16C (according to my CRC) and then add this to a solution of calcium chloride you should make the oxalate free from any carbonate contamination. Means redoing the math I'm afraid.

The product will probably be the hydrate, which may be dehydrated by heating to 200C (again according to CRC, air excluded I would think), is it certain the product used for fireworks is anhydrous?

Obligitory remainder about oxalic acid and its soluable salts being poisonous and the importance of washing hands.

A lot of power supplies can't regulate all the way to zero current and are damaged by running with no load. This page has a method that looks sound. Shorting green to ground should do it, somewhere I have a note of the pin number on the motherboard connector.

http://www.wikihow.c...ab-Power-Supply

There is a £13.67 500W (30A 5v line) EZcool power supply which has a very bad reputation and an 800W (51A 5v line) Storm PSU for £26.42. I'm looking at scan computers prices.

The electrolytic cells I made (long time ago now) were very non linear in current draw. These weren't chlorate or perchlorate cells but I'm concerned that a fixed voltage regulated power supply will either not run the cell or be in overload. It may be possible to modify the circuit of an ATX supply. If the coils can be rewound this could provide a huge amount of current for the money. Modifying a commercial PSU seems no more hazardous than building a supply from scratch.

The easier DIY designs have some drawbacks, like a live output if the transistor latches in the buck converter. I'm looking into safer designs like a flyback converter. Schottky diodes have the drawback of low voltage ratings. The biggest advantage of going this route is that you can control how the power is regulated.

Rewinding a microwave oven transformer seems like a good plan, compllete microwave ovens in the 700-800W range are available from astonishingly low prices £35-40. These would have transformers inside rated over 1kw. I haven't been able to find the transformers cheaper then the oven so far. They aren't magnetically limited and could waste a lot of power if the secondary voltage is wrong. At high current 50A+ a single diode could have a drop of 2V.

I'm still scratching around in a lot of directions. This thread has sparked a lot of ideas.

Wow, well done Sir. What size stars in what size shells?

Well, for one thing, lead acetate is cheaper. It's also less dangerous to handle, as long as you don't eat it, while aluminium dust is very harmful.

Lead has a long biological half life and soluable salts can be absorbed through the skin. They also taste sweet, which could cause other problems. I'm reminded of the mention in Davis of the deaths caused by mercury snakes.

Copper (I) is unstable and will naturally disproportionate to CuCl2 and Cu metal.

No, but it will react with oxygen in the air.

They do not emit bands of light, rather discrete wavelengths.

Atomic emission tends to be very narrow, observable linewidths tend to be dominated by doppler effects. Moleculer emission tends to happen in wider bands.

Table seems to be missing some details, there are a lot of mentions elsewhere of bright bands for CuCl under 460nm but I can't find details.