No, I didn't forget. Each 1 liter batch of B stock solution contains 105 grams of sodium sulfite. When you dilute that by placing 100 ml of that B stock into 1 liter of working solution (1:10, since 100ml is 1/10 of 1 liter), you end up with 10.5 grams of sodium sulfite in the 1 liter of working solution. To substitute 0.4 grams for this is to be short on Solution B by more than an order of magnitude. Just what am I missing here?