Views: 75
Classification of Laboratory Apparatus
Laboratory wares can be classified Into:
- Glassware,
- Plastic wares
- Ceramic wares
- Platinum wares
1. GLASSWARE
Most apparatus found in the laboratory are made from glass.
Glass have several advantages i.e.
- They are transparent and easily graduated or calibrated
- They are inert towards most laboratory chemicals except hydrofluoric, phosphoric acid and some alkalis.
- They are bad conductors of heat and thus resist changes in temperature.
- They have smooth but hard surface, which is easily cleaned.
- They can easily be molded into the required shapes.
- They are light and easy to carry.
They however have some disadvantages i.e. they are fragile and therefore can break easily.
CLASSIFICATION OF GLASSWARE
Laboratory glassware can be classified according to:
- The material they are made from.
- The purpose for which they are intended.
Classification According To Material
There are two types of glass i.e. soft glass and hard glass
(i) Soft glass (soda glass)
They have high percentage of sodium oxide and low percentage of silicon oxide, it melts easily when heated and it is used to make pipettes and glass tubing.
(ii) Hard glass (Borosilicate glass)
They have high percentage of silicon oxide and low percentage of sodium oxide. It also has boron oxide.
They are highly resistant to heat hence do not melt easily. They are used for making beakers, flasks and most laboratory apparatus
Borosilicate glass have high mechanical strength i.e. they do not beak easily, fairly inert to chemical have high resistance to thermal shock, high melting point and softening point
Classification According To Purpose
- General-purpose glassware
These glassware are not calibrated. They are used for various jobs that do not require measurements e.g. test tubes, beakers, flasks etc.
- Special purpose glassware
They are designed to perform only specific jobs e.g. density bottles, condensers etc.
- Standard, jointed, or quick fit glass wares
They are glassware with interchangeable ground joints e.g. distilling flask, soxhlet extractor’s etc. they are suitable for general use in preparative organic chemistry
- Volumetric glassware
They include burettes, volumetric flasks and pipettes. They are used to deliver or to contain a specified volume.
They are graduated as either EX to mean they deliver or IN to mean they deliver a specified volume. The temperature of calibration is also shown is also shown on the glassware (usually 20 o c). to show the optimum temperature in which they shall give accurate volume Volumetric glassware are also classified as class A or class B. Class A have an error tolerance of ± 0.001 cm3 at the stated temperature while class B have a tolerance of ± 0.010 cm3 at the stated temperature
1. PLATINUM WARES
Apart from glassware, platinum forms part of the laboratory wares. They are used to make crucibles etc.
Platinum wares are mixed with small quantities of Rhodium, Indium or Gold to give them strength.
They are inert to most chemical reagents, have high melting point i.e. 1770 o c and have excellent conductance of heat and extremely small adsorption of water vapor.
Platinum crucibles are virtually indispensable for accurate experimental analysis. They must be used with care because they are expensive.
They should be kept chemically clean and always avoid reagents in which platinum is soluble e.g. aquaregia, HCl, liquids mixtures which evolve bromine or iodine, concentrated H2SO4 and H3PO4.
When heating, its base should be above the blue core of the flame otherwise they would become brittle and break.
Crucibles should be supported on clay triangles when heating
The process of cleaning crucibles is called tarring
2. PLASTIC WARES
Plastics wares provide viable alternatives to glass wares
- Plastics generally have excellent chemical resistance to most laboratory chemicals at room temperature, besides being inert to acids, bases and peroxides.
- Apparatus made from plastic are long lasting and less expensive.
- Plastics materials are difficult to wash and rinse after experiments.
- They cannot be used in heating and in doing other specialized laboratory work especially in organic chemistry since most of them are easily attacked by organic solvents.
- They include wash bottles, beakers, measuring cylinders’ reagent bottles, funnels etc.
3. CERAMIC WARES
Ceramic wares have very high mechanical strength and high resistance to heat and chemical attack.
They are however heavy and expensive, therefore, limited to making pestles, mortars and white tiles used during titration in chemistry.
Ceramic wares are cleaned using a detergent solution or abrasive powder, which do not scratch the surface.