§ 320. Standard of purity. The gas furnished or supplied by any
corporation, association, partnership or person in any city of the
second class shall be free from sulphuretted hydrogen, to be determined
by exposing for thirty seconds a slip of white paper saturated with
acetate of lead to a jet of gas flowing about five feet per hour, and
each one hundred cubic feet shall not contain more than ten grains of
ammonia nor twenty grains of sulphur.