Jim::
To answer Steve W.’s question: “How much dry chlorine would be needed to make a one gallon batch of standard 5.25% chlorine bleach?”:
In the conversion of dry hypochlorite to liquid (bleach), since all the percentages are by weight, it is easy to calculate the amount needed to reconstitute 5.25% hypochlorite bleach. Since dry is about 55% active, it should be diluted roughly 10-fold by weight (one pound to 10 pounds water). So, you would need 8/10 pound or about 12 ounces per gallon of reconstituted liquid bleach. Then the standard formulas could be applied for the final mixing with water for sanitizing.
Safety Warning: Be very careful when mixing dry hypochlorite with water, add it slowly and watch for overheating and beware of splashing. Wearing goggles for eye protection is mandatory! Cheers. – JB in Nashville