When I was confined to Christ's Church School for Wayward Boys I was told that they put saltpetre [potassium nitrate] in the mashed potatoes, especially if we were going to a dance at St. Margaret's School for Wayward Girls or if they were coming [ha] to our school. I never seemed to have any problems, functionally, and I loved the mashed potatoes. BTW, both schools were [and still are] run by the Episcopal Church in Virginia.

JR