This is a low current battery. The surplus computer disk surfaces contains cobalt which is believed to be the positive potential source. The magnesium is the negative potential. The epsom salt (along with fluoridated water) is the electrolyte. The ratio of epsom salt to water is 1 of 3 currently; ie, 1 cup to 3 cups water. The LED is a unknown ID of chinese origin. The LED “seems” to act as a ~ zener diode; as the ~ usual voltage is typically 2.7 volts across it. The magnesium does emit a very low volume of gas.