DANBURY, Conn.--(BUSINESS WIRE)--Praxair, Inc. (NYSE: PX), a global leader in the production and supply of helium, announced today that it has taken another step in enhancing its helium supply portfolio by signing a long-term agreement for the purchase of helium from Nacogdoches Oil & Gas (NOG). NOG operates a helium-bearing gas field in Apache County, Arizona, and will supply up to 100 million scf per year of helium under the agreement, with the potential for further expansion. “Developing