This apparatus is made of polyethylene has three main portions. The top portions is fitted witha thistle funnel and a bulb structure through which dilute acid can be poured will reacts with a metal sulphide in the base of the Apparatus. HS gas then evolved collects in the middle dome from where it can be released through a leakproof stopcock fitted with a self lubricating PTFE plug. The base is provided with a residual outlet fitted with a cap for easy cleaning.