Greasing the Joints

Inserting Adapter Upside Down Sans Glass 

I don t know whether to relate this problem (Fig. 26) to glass forgetting, or upside-downness, since it is both. Help me out. If I don t see you trying to use an adapter upside down without the glass, I won t have to make such a decision. So, don t do it. 

In all my time as an instructor, I ve never had my students go overboard on greasing the joints, and they never got them stuck. Just lucky, I guess. Some instructors, however, use grease with a passion, and raise the roof over it. The entire concept of greasing joints is not as slippery as it may seem. 

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Grease all joints, no matter what (see Greasing the Joints ). Under vacuum, it is easy for any material to work its way into the joints and turn into concrete, and the joints will never, ever come apart again. 

Fig. 11.12a. When using a pig, remember to grease the joint lightly, around e outer edge only, so that the receiver can be rotated while under vacuum. Also fix the receivers securely using clips.

Fit the rubber tubing onto the condenser (p. 117), lightly grease the joint on the still-head and refit the condenser, clamping it firmly into place. 

Assembling the Apparatus. You should not grease the joints when assembling the apparatus. Ungreased joints seal well enough to allow you to perform a simple distillation. Stopcock grease can introduce a serious contaminant into your product. 

NOTE Normally, you should not grease joints. It is necessary to grease the joints in a vacuum distillation only if you cannot achieve the desired pressure without using grease. 

Assemble both condensers and the cone/flexible tubing adapter whilst hot as shown in Fig. 6.2 (grease the joints carefully and use green clips to secure them), connect the cone/flexible tubing adapter to the vacuum/ nitrogen manifold and turn on the flow of nitrogen. 

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