Glassware Taper Joint Measurement

Years of work outside laboratory environment seemed made me clueless about many simple laboratory terms and methods. I think I have forgotten many important rules and protocols. I feel that I am not fit for this kind of work anymore. I wish my doubt is not true.

I need to order three flat bottom boiling flask as replacement part for traditional Soxhlet Extraction System – an equipment to measure crude fat or simply oil content.

The problem! I forgot how to measure the glass standard taper joint, the ground inner/outside finish for easily connecting glasswares together. The joint size is usually permanently written on surface but I cannot find it anywhere.  Or, maybe I never knew how to measure it from the very start. I was absent when our Chemistry professor discussed it.

At times like this, back reading is my best friend.

Glassware standard taper joint looks like this.

flat bottom flask ground jointAfter reviewing few paragraphs: The size is expressed by two numbers separated by forward slash. The joint size 19/22 means 19 mm width of the joint widest portion and 22 mm taper length. Get outside width  for male joint and inner for female socket.

It is recommended to use vernier caliper for accurate measurement. Search for matching product on-line or on catalog books. If no similar products are found, then it is probably out of stock or you have made a wrong measurement.

vernier caliper soxhlet and flask


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