Test tubes with side arms, made from borosilicate glass, serve various purposes in laboratories. Let’s delve into their uses and significance:

1. Chemical Experiments:

   • Test tubes are fundamental tools in chemical laboratories. They allow scientists to test the properties of various chemicals and gases.
   • The side arm feature provides an additional opening, which can be useful for adding reagents, connecting to other apparatus, or collecting gases.

2. Microbiology Applications:

   • In microbiology labs, test tubes with side arms are employed for several tasks:
     • Preparing Culture Media: These tubes are used to mix and sterilize culture media for growing microorganisms.
     • Sample Collection: They facilitate the collection of samples such as blood, urine, or other biological fluids.
     • Holding Fluids: Test tubes hold liquids during various stages of experimentation.

3. Design and Structure:

   • Test tubes are closed at the bottom and open at the top.
   • The bottom of most test tubes is slightly curved or spherical.
   • They come in different sizes, ranging from small (Durham) tubes to large culture tubes.
   • The standard size used in laboratories is 18 mm wide and 150 mm in length.
   • Other sizes include:
     • Extra Small (Durham) Tube: Used for detecting gas produced by microorganisms.
     • Small Tube: Holds approximately 9 ml of material.
     • Medium Tube: Holds around 22 ml of material.
     • Large Tube: Can accommodate 28 ml of material.

4. Material Types:

   • Disposable Test Tubes:
     • Made of various plastics (nylon, polyethylene, polypropylene, etc.).
     • Resistant to UV light and different temperature ranges.
   • Reusable Test Tubes:
     • Made of glass (borosilicate, fused silica, or quartz glass).
     • Highly resistant to temperature (autoclavable) and tolerate chemicals.
     • Transparent but more costly than disposable ones.