to the brine solution 26 the description hereinafter refers to chlorine gas produced by this apparatus but it is understood that other halogen gases ca be produced by changing the salt content chlorine gas 28 bubbles up through the gas separator column 20 to a tube 30 having a gas tight connection 31 to the top 32 of gas separator column 20 tube 30 leads to a catchment basin container 34 where the chlorine gas may mix with liquid caustic 36 overflowing into the catchment basin container 34 from the cell 12 the container has a tube 38 which leads to a liquid to be sanitized such as a swimming pool alternatively tube 38 can lead directly to a tank for storage or direct use of the chlorine gas 28 a hydrometer body 40 is floatably disposed within the caustic 36 and moves in an upward direction as the density of the caustic 36 increases this upward movement causes plate 41 supported by rod 43 to redirect a water stream from nozzle 46 and allow water to deflect through hole 45 into the caustic 36 a float 42 is attached to a plate 44 as the float 42 moves downward in response to decreased caustic level from.