Semimacro method is more convenient than macro. This is because the Semimacro method requires less amount of reagents. In this way a lot of work can be done quickly. In the laboratory, hydrogen sulfide gas is prepared in a macro method with the help of a gas keeper , which disperses in the air during flow. It causes considerable physical harm to students when they inhale it. The semiacro method uses thioacetamide instead of hydrogen sulfide. It reacts with water to produce H2S ( hydrogen sulfide) gas in solution , almost all of which remains in the solution or reacts , thus not polluting the environment of the reaction zone.