Heating mantle holding

Clamp the flask (around the neck) a few inches up the ringstand (Fig. 68). We are using heating mantles and you ll need the room underneath to drop the mantle in case it gets too hot. That s why the flask is clamped at the neck. Yes. That s where the flask is ALWAYS clamped, no matter what heat source, so it doesn t fall when the mantle comes down. What holds the mantle Extension ring and clamp fastener. 

The lid was then bolted shut. Using the precalibrated ammonia sample cylinders, the predetermined amount of liquid ammonia was delivered to the vessel. The vessel was heated by a 400-W Parr heating mantle to the desired temperature. After holding the vessel at the target temperature for the selected residence time, the exhaust valve was rapidly opened to relieve the pressure and accomplish the explosion. Both pressure and temperature drop very rapidly. The treated samples were removed and allowed to stand overnight in a fume hood to evaporate the residual ammonia. 

The only place it could go—down. Remember that the mantle is constantly mixing with the ocean at subduction zones and injecting hot gases and metals through vents. The crust serves as a blanket to hold this heat in, but the blanket leaks, so the mantle is slowly coohng off. Konhauser calculates that, at this point in prehistory, the mantle cooled past the point where nickel would stay liquid. Instead, the nickel solidified and sunk down, away from the surface and out of the oceans (Figure 6.5). 

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