with the general formula Na&,
where x = one to six and is an average
value for a particular product. In solution
all possible S," ions (S=, SZ',
S3= . . . . S6=) are in equilibrium not only
with one another but with sodium hydrosulfite
as well, cf. Eq. 1. The principle
effect is that as the average value of x
increases, the amount of hydrosulfite and
its accompanying caustic soda are both
diminished, resulting in a lower pH. At
chemically equivalent concentrations, solutions
of sodium sulfide (8 grams per
liter) and sodium tetrasulfide (17 grams
per liter) have pHs of 12.2 and 11.6
respectively, while at 8 grams per liter
sodium tetrasulfide has a pH of 11.4.
Polysulfides act not only as pH buffers but
also as antioxidants.