Thorne’s still list generic oxalic acid, but you have to search for it rather than drilling down through the Health & Feeding … Varroa sub-menus which only now list proprietary products. They also still list the pre-made solution at the recommended 3.2% strength for mid-winter trickling, but remember that this has a limited shelf-life. You’ll be pleased to know that this is my final post on this topic for a bit … 😉
Alternative sources and alternative uses
If you’re wondering where to purchase oxalic acid to keep the wooden decks of your dinghy, motor launch or even your local association yacht looking sparkling clean and ship shape (pun intended) you could do a lot worse than look at Darrant Chemicals. Small, medium and large quantities of 99.6% pure oxalic acid dihydrate are available at very reasonable prices with blisteringly quick delivery.
25kg of oxalic acid is less than £50 delivered to mainland UK*, enough for even the largest association (yacht). They also sell via eBay (as solvent-shop) but it’s cheaper to deal direct.
You may already know this company as a source of chemicals for your beekeeping, rather than yachting, needs. For example, they also sell acetic acid which is ideal for fumigating brood and super comb in late autumn or winter, killing Nosema spores, chalkbrood and wax moth (as described in this PDF from the National Bee Unit). Both acetic acid for sterilising comb and oxalic acid for scrubbing decks must be used with care.
I’m sure there are other suppliers (perhaps even your local yacht chandlers?) and they might even be cheaper, but I’ve purchased from Darrant and been pleased with the service.
* of course, if you made the mistake of purchasing a similar quantity of Api-Bioxal (a VMD-registered miticide, 88.4% of which is oxalic acid) to clean the decks of your motor launch it would cost more than £5300 😉