so the answer is: close the dispensing funnel of the piston, the Open the stopcock a and b, close the stopcock c, use your hand to cover the heat (or slightly hot) round bottom flask A, if there are bubbles coming out of C, after removing the palm of your hand (or heat source), water rises in the conduit at C, then it proves that the A device is well airtight;
(2) the first to make the gas filled with B, with the gas in the B for the test, according to the role of the airbag B is to collect the gas, in order to control the flow rate, from the design of the dotted line box (3) A device produces sulfur dioxide gas, sulfur dioxide can make the magenta solution discoloration, so the answer is: magenta solution discoloration;
(4) the inlet end of the skimmer blue lightening, the outlet end of the skimmer blue unchanged when the outlet is out of carbon dioxide