Hydrogen sulfid: H-S-H or H2S

Sulfur dioxid: O=S=0 or S02

"The carbon atom has four hands, and atoms of nitrogen and
phosphorus have five hands, but sometimes use only three. Thus, in
the compound called ammonia, one atom of nitrogen always holds three
atoms of hydrogen; so, if you buy seventeen pounds of ammonia you
would get only fourteen pounds of nitrogen and three pounds of
hydrogen. This means that, if the two-eight-two fertilizer contains
two per cent. of ammonia, it contains only one and two-thirds per
cent. of the actual element nitrogen, and a ton of such fertilizer
would contain thirty-three pounds of nitrogen. In other words it
would take six tons of such fertilizer to replace the nitrogen
removed from one acre of land in four years if the crop yields were
fifty bushels of corn and oats, twenty-five bushels of wheat, and
two tons of cowpea hay."

"Six tons! Why, that would cost a hundred and fifty dollars! Well,
well, I thought I knew we couldn't afford to keep up our land with
commercial fertilizer; but I didn't think it was that bad. Almost
forty dollars an acre a year!"

"It need not be quite that bad," said Percy. "You see this
two-eight-two fertilizer contains eight per cent. of so-called
'phosphoric acid' and two per cent. of potash, and those
constituents may be worth much more than the nitrogen; but, so far
as nitrogen is concerned, the two hundred pounds would cost from
thirty to forty dollars in the best nitrogen fertilizers in the