try these:

http://www.cr.nps.gov/museum/publica...gram/14-09.pdf

http://www.cr.nps.gov/museum/publica...gram/14-08.pdf

http://www.nedcc.org/leaflets/nitrate.htm

go down to appendix M:

http://www.cr.nps.gov/museum/publica...I/mushbkI.html

good luck--KT