Hoffman s voltmeter apparatus rvfm ch0740b hoffman s apparatus is used for demonstrating the decomposition of water determination of chemical composition by electrolysis and has applications in the evaluation of the electrochemical equivalent of hydrogen the glass unit has two connected limbs each of approximately 50ml capacity graduated 2 to 50ml integral reservoir tube and funnel shaped bulb with a stopcock at the top of each limb rvfm hoffman s complete