A Simple Conductivity Water Cut-Off Switch Despite the considerable sophistication hrought into the chemical laboratory over recent years, experimental work still remains vulnerable in some places to such simple incidents as electricity or water failures. This is especially critical if common and time-consuming chemical procedures such as refluxing are to be performed, as these are frequently conducted overnight, unattended, and often involve heating inflammable solvents to their boiling temperature fur long periods of time. We have developed a simple, automatic safety system which largely removes the hazards of water failures. The system (Fig. 1)takes advantage of the electrical conductivity of tap water for omration. Water flow throueh the svstem can be controlled bv a simde restrictor. such
an a ~ m r i l t ~ hratine d svstem. The svstem is orotected aeainst sudden variations in water -" pressure by a safety drain (C) with a larger diameter (1.5 em) than the inlet tube (B, 0.7 cm). This systemavoids the hazards ofworking withmercury switchesland should be easily accessible to every laboratory for the modest investment of $5.00.
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