I started looking for an alternative to crucibles in 90s. CLEAPSS (www.cleapss.org.uk) were receiving repeated reports of poor results for the magnesium/oxygen reaction carried out in crucibles because students could not lift and replace the lids quick enough or they dropped the lids and they broke; that was caused by tongs not closing correctly because they had been “vandalised” in previous classes. Also crucibles would crack apart on cooling. Using stainless steel and nickel crucibles on a class basis were the only alternatives available but they are expensive. When I heard that Worcester Royal Porcelain where shutting down their crucible-making section, I phoned to ask about it.
“Not a week goes by without a school teacher or technician phoning us up to complain about the quality of porcelain crucibles because they broke, or they could not be cleaned to their original state. Don’t teachers know they are only supposed to be used once?” In fact it appears they were used to remove samples of molten steel from a furnace for analysis.” When the steel industry collapsed, so did the crucible market in the UK. “Oh” I stupidly said “So you do not just make them for schools”. "No, it was only a fraction of the market" was the reply.
I get excellent results for the oxidation of magnesium (Fig 3). See https://www.youtube.com/watch?v=d8QWXCaXfSs. It amazed me that bottle-tops fitted snugly into a small pipe-clay triangle. Remember that you do need to burn out the plastic insert in the bottle top before proceeding further. This is best done in a fume cupboard or out doors on a camp fire (as done in Uganda).
Could the bottle-top be used as an open crucible for activities such as the reduction of copper oxide with carbon? Unfortunately it is difficult using tongs to pick up hot bottle tops and I ended up with hot solids all over the bench.
I also visit the local DIY and cookery shops regularly just to see if an idea triggers off in my head. In the tools section were pliers at 0.99p (Fig 4), cheaper than tongs from educational suppliers, sturdier without that weak central hinge and most important, (Fig 5) easier to grip. But how do you hold a crown-bottle top with pliers? Feeling inspired on my Saturday morning shop, I looked further and found nuts and bolts and so here was the equipment. A crown-bottle top with a hole and inserted through the hole is a nut and bolt (Fig 6). The bolt is held with the pliers or a clamps. I do tend to forget what I originally went in the shop to buy.
Here is an example of its use in finding the percentage water in hydrated salts (Fig 7), https://www.youtube.com/watch?v=3b1V38YV0wo. The use of a spirit burner is often questioned, afterall UK labs have methane gas supply and Bunsen burners. The spirit burner avoids further decomposition of the anhydrous salt, eg metal sulfates to oxides, sulfur dioxide and sulfur trioxide. Helpline calls to CLEAPSS have regularly reported children suffering breathing issues in class from this reaction being taken too far.
Now by using the hand held bottle-top deflagrating spoon or the nuts & bolt bottle top crucible with plier , you can heat carbon and copper(II) oxide, see the reaction and neatly place the hot bottle-top with products on the surface of water (do not sink it) (Fig 11). The copper formed in the reduction has not re-oxidised and there is a beautiful sample of copper metal. It can be carried out with iron(II) oxide to make iron which is magnetic.
So should you buy expensive nickel crucibles? The only regular use I have for nickel crucibles is a demonstration of the fat pan fire but it is always useful to some in the labs but a class set? I really do think it is necessary..
There are more ideas on the other pages of this website www.microchemuk.weebly.com.