Answer: Saltpeter can be helpful in starting seeds with a very hard seed coat; it is also a way of simulating the chemical treatment a seed would undergo while in a bird's digestive tract. Using it for pepper seeds would not usually be necessary, but it could be helpful, epsecially if the seeds are old and very dry or if the temperature is a bit low.
In my experience, most pepper seeds can be started into growth very quickly by using a barely damp sterile soilless mix, barely covering the seed, covering the pot with plastic wrap and setting it in a bright location out of direct sun and then applying gentle bottom heat to warm the soil temperature to about 75 - 80 degrees.
In my experience, too, fresher seed usually germinates faster than older seed and some varieties of peppers are simply slower than others -- conversely some will pop right up in about four days.
If you use a search engine such as google and search for the terms saltpeter and pepper seed or seed germination you will find numerous references to its use.
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