Keck clamp

I) polyethylene wash bottle (m) single-pan electronic balance with automatic zeroing and digital readout, 100 g 0.001 g capacity (n) electric flask heater (o) solid-state control for electric flask heater (p) stainless steel spatula (q) Keck clamp. 

Plastic joint chps or Keck clips (Fig. 5.22a) are used for holding ground-glass joints firmly together and may be used to replace clamps and support stands at certain points when building apparatus (see p. 109) and are essential when using rotary evaporators (p. 122). The main weakness of these otherwise useful devices is that they soften at about 130°C and this may allow the joints to separate. Therefore they should never be used at the hot end of a distillation, for example. The clip should be used to hold a distillation adapter on the end of a water condenser, or the flasks onto a fraction collector, but never on the distilling flask or to hold the condenser onto the still head (Fig. 5.22b). 

The temperature of the air stream emerging from a heat gun is commonly from 300 to 500 °C, far higher than that of the typical hand-held hair dryer. Consequently, you must use the heat gun prudently when drying apparatus held by plastic-containing devices such as Keck clips or clamps with rubber- or vinyl-coated jaws (Fig. 2.5), because the plastic can melt. 

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