When sparked, IRON will electrolyze any nearby WATR, SLTW, or DSTW (the water will be turned into a mixture of HYGN and OXYG). Note that WATR or SLTW will cause the IRON to rust - to prevent this, place some GOLD near the IRON, or electrolyze DSTW instead of WATR/SLTW
You can use the wiki section of website anytime,it has very usefull informations.

@SandvichEater (View Post)

 Yeah, mostly what cracker1000 said. TIP: You can just build a beaker with 2px thick walls, the first layer IRON, the second GOLD. Oh and maybe put some PTCT nearby. When the PTCT is sparked, the spark is transferred to the GOLD and IRON, electrolyzing the water. The PTCT cools down to 22C relatively quick, so it stops water from boiling.