1.2: Glassware and Equipment
- Page ID
- 93163
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- 1.2.1: Storing Samples (Parafilm/Teflon Tape)
- When samples must be stored for a period of time, they are best stored upright in screw-capped vials. Samples may evaporate through the joint over time, and if a highly volatile sample is used, the joint should be wrapped in Teflon tape (semi-stretchy white film or Parafilm (stretchy plastic film) to create a better seal. Teflon tape is less permeable to solvents than Parafilm, and volatile samples wrapped in Parafilm may still evaporate over a period of weeks.
- 1.2B: Ground Glass Joints
- Most organic glassware uses "ground glass joints," which have a frosted appearance. They are precisely ground to a certain size (which makes them expensive) and have outer (female) and inner (male) joints so that pieces can be connected together with a tight fit. Common joint sizes are 14/20, 19/22, and 24/40. The first number refers to the inner diameter (in millimeters) of a female joint or outer diameter of a male joint. The second number refers to the length of the joint.
- 1.2C: Clamping
- Metal clamps are used to connect glassware to ring stands or the metal lattice work. Two common type of clamps are "extension clamps" and "three-fingered clamps". Although in many situations the clamps can be used interchangeably, an extension clamp must be used when clamping to a round bottomed flask as 3-fingered clamps do not hold well.
- 1.2D: Greasing Joints
- Ground glass joints are manufactured to fit quite well with one another, and yet they are not perfectly airtight. In some situations (e.g. when using reduced pressure inside an apparatus), grease must be applied to each joint to ensure a good seal. Grease is also used whenever the joint may be in contact with a highly basic solution, as basic solutions can form sodium silicates and etch glass.
- 1.2E: Cleaning Glassware
- Glassware should be dismantled and cleaned as soon as possible. Experience with home dishwashing can tell you that dishes are more difficult to clean when allowed to dry. If there is a time constraint, it's best to leave glassware in a tub of soapy water.
- 1.2F: Drying Glassware
- Glassware that appears "dry" actually contains a thin film of water condensation on its surface. When using reagents that react with water (sometimes violently!), this water layer needs to be removed.