Sorry Chillwinston - I had no intent to criticise, but merely to respond to your post that said:
"Realise its no help to a facinating subject and confirm it was a MAS a/c that was written off due to hull loss concerning the leakage of mercury, think it was A330"
Hydroxywhatsit is undoubtedly vile stuff but it is an organic compound that one might reasonably expect to be nasty, rather than a somewhat bizarre liquid metal like mercury with which one used to play in misguided innocence in one's youth.
And believe me as an all too frequent pax I give great and continuous thought to the many things that might be lurking beneath the floor, and hope that they are indeed properly packaged and contained.
I've also learned through several years of enjoyable pruning that there is rarely such a thing as getting off thread - even the introduction of red herrings as a red herring is fair game, methinks!