I did a brew last night and after pouring the wort into the fermenter i realised I'd forgotten to empty out the sanitizer i'd put in it. It was about 300 ml of Chemsan (described as "A blend of phosphoric acid, benzenesulfonic acid and isopropanol.") (that is, 300 ml of the diluted sanitizer, which, since it has a 2ml to 1 litre dilution ratio, about 0.6 ml of the undiluted sanitizer). So, this ended up mixed in with about 30 litres of wort.
That comes out, assuming that it doesn't settle to the bottom or evaporate out or something like that, about a teaspoon (5ml) per pint. Chemsan is a "no rinse" sanitizer, which I assume means it's not super toxic, but I assumed that meant if there's a small residue left on a surface, rather than a whole teaspoon poured into a pint, so to speak.
I'm going ahead with the brew anyway, but this beer was intended for a friend's party (how typical that it would be the one i potentially poison!), and I was just trying to get a handle on the risk involved.
The instructions say:
Apply diluted solution on surfaces with a cloth, mop ,brush, sponge, spray or by immersion. After 2 minutes contact time, drain solution thoroughly. For all applications, allow to air dry, however surfaces must remain wet for at least two minutes. Do not rinse after Chemsan application.
The "do not rinse" thing kind of suggests that it's not going to poison anyone, but like I say I think they were talking about a thin residue on a surface.