Experiment 18.5a, part 4 requires polyethenol.
Here is a helpful message from Peter Borrows at CLEAPSS.
You can't buy polyethenol, but you can buy polyvinyl alcohol, which is the
same stuff. (Some people also call it PVA but you need to be careful about that as PVA can also mean polyvinyl acetate, ie, polyethenylethanoate.)
The Nuffield name is the correct scientific name but industry (and American firms) tend to use the older name.
You can get it from Aldrich (tel 0800 717181). There are quite a lot of different products listed, differing in molar mass. I don't think it matters too much for the purposes of this experiment which product is used, but as the Nuffield Chemistry Student's Book refers to the molar mass as 105 g mol-1, they would be best to pick the product with the ‘average molecular weight’, Mw, closest to this, ie about 100 000. As it happens that is also the cheapest (thank you to Mike Vokins).