Laboratory rubber stopper

A laboratory rubber stopper or a rubber bung is mainly used in chemical laboratory in combination with flasks and test tube and also for fermentation in winery.[1] [2] [3] Generally, in laboratory, the sizes of rubber stopper can be varied up to approximately 16 sizes and each of it is specific to certain type of container. As the rubber stopper is used in many experiment, some specific experiment requires a specific material. For example, the M35 Green Neoprene is for chemical resistance. For food fermentation, M18 white natural gum is preferred. For high temperature application, red or white silicone rubber stopper should be used.

(From left to right) One-hole Rubber bung size 10, Two-hole Rubber bung size 14, and Solid Rubber bung size 16

Sizes

Rubber bung can have one or more hole(s) for plugging in tube depending on the specification of the procedures. To prevent the liquid chemical leaks or escape the container, the rubber bung should fit tightly to the container's opening; the dimension of the rubber bung is of concern. These are some of the sizes that are commonly seen in chemical laboratory.

(From left to right) Rubber bungs are aligned from size no. 1, 2, 3, 4, 6, 7, 8, 9, 10, 12, 13, 14, 15, to 16, respectively. (Comparing to the ruler)
Size No. Top
mm		 Bottom
000 12.7 8.212x75 test tubes
00 15 10
0 17 13
1 19 14
2 20 1620x150 or 10ml test tubes
3 24 18
4 26 2025x200(150) or 20ml test tubes
5 27 23 50 ml Flasks
6 32 26 250ml Erlenmeyer Flasks
7 37 30 500ml Erlenmeyer Flasks
8 41 331000ml Erlenmeyer Flasks/ Florence Flask/ Filter Flask
9 45 37 1000ml Erlenmeyer Flasks/ Florence Flask
10 50 421000ml Filter Flasks

2000ml Erlenmeyer Flasks/ Florence Flask

11 56 48
12 64 54 4000ml Filter Flasks
13 68 58
14 90 75
15 103 83
16 127 90

Additional images
  • Rubber bung size no.5 fits tightly on 50ml Pyrex® Flask
  • Other equipments such as glass tubes can be plugged into the holes of the rubber stopper

See also

References
  1. US US2669370 A, Royall, "Rubber stopper", published 1954
  2. US 2196785 A, Ei, "Rubber stopper for bottles, jars, vessels, and like containers", published 1940
  3. Patent 2,289,677 US Patent 2,289,677, Perelson, "Rubber stopper", published 1942


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