How do you test a co2 cylinder?

Measure the weight of the full cylinder and note down as m1
Note down the tare weight of the cylinder marked on the cylinder and note down t1
the m1 - t1 = M the weight of gas in Kilograms
multiply the wt of gas in Kgs with 0.9403 ie. M x 0.9403 gives the total cubic meter of acetylene gas in cylinders

Note: One gram of Acetyle gas measures 0.9403 litres at 27 degree centigrade and 760 mm of Mercury pressure.