this apparatus is made of polyethylene has three main portions. The top portions is fitted with a thistle funnel and a bulb structure through which dilute acid can be poured which reacts with a metal sulfide in the base of the apparatus. Hs gas then evolved collects in the middle dome from where it can be released through a leak proof stopcock fitted with a self lubricating ptfe plug. The base is provided with a residual outlet fitted with a cap for easy cleaning. In size : 250,500 & 1000 mm