The Iowa Senate voted 45-0 Monday to add four products to a list of controlled-substance ingredients that potentially could be used as “precursors” in the production of methamphetamine. Items covered under House File 159 included sodium hydroxide, ammonia nitrate, ammonia sulfate, and light or medium petroleum distillates. The bill will return to the Iowa House, where its passage is expected en route to Gov. Terry Branstad’s desk after senators made a minor change to make the effective date 2014 rather than 2013. Backers said the measure is intended to address the fact that some meth producers have switched from a “two-pot” method of production to a “one-pot” method using different ingredients. The substances covered by the bill would need to be altered from their original states to prove an intent to manufacture meth, supporters said.