I have run this around 10 times now, in a 2.5l paint can, trying various different methods of insulation. I am using NaOH and I've also used KOH. NaOH melts a little lower than KOH, closer to the melting point of benzoate. To find your values, devide the mass of benzoate by 144.14. Then times the result by 39.9 for the number of grams of NaOH you will need, and 56.1 if using KOH. Use an excess of base. Buy the base in 5 kilo tubs or by the sack at this scale to save some £££ on buying it in half and 1 kilo packs at the DIY store. A major problem with bulk methods is trying to heat the can through. As the mixture reacts, it insulates the base of the can and blocks heat getting from to the top. With larger containers and masses, the surface area to volume drops, making it harder to pass the heat through without warping or melting the can. Simply using a bigger burner won't do much to solve this. The copper tube is fixed to the can by a 15mm compression plumbing part called a 'tank fitting' or 'tank coupler'. This has one compression olive for fixing the 15mm pipe and then a pair of flanges, one of which sits on the inside of the can. A 20 - 21mm hole allows the flange side of the fitting to pass through where it's done up on the opposite side. It is lined with PTFE. Despite so much abuse, the PTFE and fitting are still perfectly all right. The can, on the other hand, is now looking like it's on it's way out. A particularly big mistake I made on the second run was to ...
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