I've got a batch of Carignane wine aging in the carboy right now and
have a question about how much sulphite to add at each racking. Here's
what I've done so far:

50 ppm sulphite at crush, 50 ppm sulphite at the first racking (after
ML fermentation was finished in November). My plan is to do a 2nd
racking, adding oak chips, then leave it till the Fall - do a 3rd
racking then bottle a week or so later.

Given the sulphite I've already added, how much should I add at the 2nd
and 3rd rackings? pH is 3.55-3.60.

Thanks!