Lecture 3 - Laboratory Equipment Flashcards
Advantages of using plastic labware
- Less expensive
- More durable/unbreakable
- Glass can be damaged by certain chemicals
Disadvantages of using plastic labware
- Permeability to water vapor
- Evaporation
- Absorption of dyes, stains, or proteins
Advantages of using glass labware
- Less permeable and less absorption
- Easily washable and reusable
Disadvantages of using glass labware
- More expensive
- May corrode or break over time (some reagents may eat away at glassware)
Borosilicate (Thermal-Resistant) Glass
Commercially known as Pyrex, this glass is the most common in laboratory grade glassware.
Resistant to heat, corrosion, and thermal shock.
Alumina-Silicate Glass
- Used for high precision analytical work
- Radiation resistance
- Used for optical reflectors and mirrors
- Not common for lab glassware
Acid-Resistant and Alkali-Resistant Glass
- Used for strong acid and base solutions
- “Soft glass” - much less thermally resistant (compared to borosilicate glass)
Low-Actinic (Amber Colored) Glass
- Reduce the amount of light traveled through them
- Used for light sensitive substances
Flint Glass (soda lime glass)
- Least expensive
- Low thermal and chemical tolerances
- Variety of glassware
- Not generally used for analytical work
Disposable Glass
- Inexpensive
- Not designed to be washed and reused
- Test tubes, glass slides, etc.
Accuracy Tolerances - Class A
Class A is most accurate for measuring liquids.
Tolerances can be as low as 0.08 mL for a Class A 100 mL flask or pipette.
To Contain “TC”
Holds a calibrated volume of liquid
To Deliver “TD”
Disperses a calibrated volume of liquid
Examples of containers and receivers
Beakers, test tubes, erlenmeyer flasks, reagent bottles.
Examples of Volumetric Ware
Pipettes, volumetric flasks, graduated cylinders, burets.
Properties of Beakers
- Wide, straight-sided cylindrical vessel
- Used for general mixing and reagent preparation
Properties of Erlenmeyer Flasks
-Used for preparing reagents and titration procedures
Properties of Test Tubes
- Usually disposable
- May be made of borosilicate glass - resistant to thermal shock and chemical reactions or disposable glass
Properties of Reagent Bottles
- Reagents - chemicals used in the testing process
- Glass or plastic
- Many different volumes
When using volumetric glassware, where should the readings be made?
The meniscus of the liquid level.
Tolerance
Allowable limits within which a volume must lie.
Capacity Tolerance of 0.08 mL (100 mL volumetric flask)
Allowable limits for the volume of a 100 mL volumetric flask would be 99.92 - 100.08 mL
Uses of Volumetric Flask
Preparation of reagents or solution that require high accuracy and precision.
When would a graduated cylinder be used?
To measure volumes of liquids when a high degree of accuracy is less essential (assay/procedure dependent).
