This article is from the Food Preserving FAQ, by Eric Decker firstname.lastname@example.org with numerous contributions by others.
Salt, sugar, sodium nitrite and sodium nitrate. Salt and sugar both
cure meat by osmosis. In addition to drawing the water from the food,
they dehydrate and kill the bacteria that make food spoil. In general,
though, use of the word "cure" refers to processing the meat with either
sodium nitrite or sodium nitrate.
Sodium nitrite and sodium nitrate are the basis for two commercially
used products: Prague powders #1 and #2. Prague powder #1 is a mixture
of 1 part sodium nitrite and 16 parts salt. The chemicals are combined
and crystallized to assure even distribution. Even though diluted, only
4 ounces of Prague powder #1 is required to cure 100 lbs of meat. A
more typical measurement for home use is 1 tsp per 5 lbs of meat.
Prague powder #2 is a mixture of 1 part sodium nitrite, .64 parts sodium
nitrate and 16 parts salt. It is primarily used in dry-curing.
One other commonly available curing product is Morton's Tender Quick.
It is a mixture of salt, sodium nitrite, sodium nitrate and sugar. Ask
your butcher or grocer to stock it for you.