Ditto what GeiyserQ said. Unfortunately, a lot of recipes are not very specific about what curing salt means. Sometimes it's tenderquick or an equivalent (there are commercial preparations that are similar to tenderquick but have slightly different proportions of nitrate), and sometimes it's prague #1 or its equivalents (instacure, pink curing salt, quick cure, etc.) which contain 6.25% nitrate.
With some recipes you have to sort of figure out what they mean. Prague #1 is usually used at the rate of 1oz per 25lb of meat, and there's often some additional plain salt in the recipe. Tenderquick would probably be the only salt ingredient in the recipe and, for sausage at least, would be in the neighborhood of 4-8oz per 25lb meat.
Hope that helps...