10. Stannous chloride, N/20. This should be frequently standardized by
titration against a standard iron solution. One cc. of N/20 stannous
chloride is equal to 0.0028 gram of iron (Fe) estimated in the ferrous
state.
11. Sodium hydroxide, N/1. Free from carbonate. This should be
frequently standardized by titration against a standard acid solution in
presence of phenolphthalein indicator. One cc. of N/1 sodium hydroxide
is equal to 0.049 gram of sulfuric acid (H_{2}SO_{4}), or to 0.03645
gram of hydrochloric acid (HCl).