condensate is tapped from the magnesium tap hole 46 either continuously or intermittently for example each time when an upper level is reached in the overflow box 44 three plunger devices 54 in this case sliding metal shafts with discs actuated hydraulically are used for the cleaning of possible deposits in the inlet pipe 14 in the elbow and in the secondary condenser thereby to keep passageways in the condenser apparatus open the temperature of the condensed magnesium inside the crucible is kept at a level above the melting point of the magnesium the interior of the condenser apparatus is maintained at or near to atmospheric pressure and the dross is kept suspended in the molten magnesium it is therefore possible to tap the condensed metal and dross 52 continuously or semi continuously from the condenser apparatus through the tap hole 46 without interrupting metal vapour production and subsequent condensation internal surface areas of the crucible the secondary condenser and the elbow are designed to provide sufficient surface area for effective condensing the design is such that in use of the condenser apparatus the level of the magnesium bath inside the crucible allows for efficient mixing of liquid magnesium and dross and to effect a required degree of heat transfer from the inside of the condenser apparatus to the heat transferring medium a test was conducted using condenser apparatus as shown in the drawing a mixture of magnesium vapour and argon gas was supplied at a controlled rate of.