Laboratory Instrument

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    Hot Air Oven:
     Construction:
        It is double layered chamber. It is divided into 3 compartments by 2 perforated plates. Its bottom carries coils of heater. It carries on/off switch and thermostat control. It has a door.


    Operation of Hot Air Oven:
  • Put the articles to be sterilized after properly drying and packing them inside the chamber.
  • Close the door and adjust the temperature required with the help of thermostat.
  • Switch on the apparatus and wait till the required temperature is attained (160 degree celsius).
  • Wait for 1 hour and after it switch off the apparatus.
  • Wait till temperature comes down to room temperature
  • Take out the article and use them according to requirement.
Other methods of sterilization are Filtration, Radiations, Chemicals, etc.



    Autoclave
      
        Construction:
            It has a vertical gunmetal chamber with strong gunmetal lid. This lid lies over the chamber and can be air - tightened with screw nuts or rubber gasket. An air and steam discharge tap , pressure gauge and safety valve and fitted with the lid. The chamber carries heater coil at its bottom.

    
        Operation of autoclave:
  • Keep the required amount of water at the bottom of the chamber.
  • Keep the articles to be sterilized inside the autoclave. On perforated plate lying above the level of the water.
  • Close the lid of autoclave tightly and switch on the autoclave.
  • Keep the air - cum- steam discharge tap open till steam starts coming through it.
  • Close air - cum- steam discharge tap.
  • Now, wait till the pressure gauze shows 20 lbs per square inch pressure.
  • Wait for 20 minutes.
  • Noe switch off autoclave and slowly open steam discharge tap.
  • Let the steam come out for some time.
  • When pressure gauze shows zero reading, open the lid and bring out the sterilized material.


 Centrifuge Machine:
 
    Centrifuge is used to deposi rapidly particles such as cells which are suspended in a fluid. It can be done by spinning the tubes of fluid in centrifuge bucket using centrifugal force. The speed is expressed as the number of revolutions per minute.

Principle:
    This equipment works on the principle of centrifugal force.

Construction:
    The centrifuge machine consists of a central vertical pillar. From this pillar, number of arms extent diametrically across. At the end of each arm is suspended a conical metal bucket. All buckets are of same size, weight and they are exactly at equal distance from the vertical pillar. Each bucket holds centrifuge tube. These tubes are also of samesize and weight. The centrifuge tubes placed opposite each others in the centrifuge must contain equal amount of fluid. The centrifuge machine can be moved at various revolutions per minute, usually 3000 revolution per minute (RPM).


        
How to use Centrifuge?
  • Apparatus must be placed on a firm base.
  • The cups or buckets must be balanced in pairs.
  • Test tube should be matched against one another in respect of size, weight, thickness of glass content, etc.
  • Centers of gravity of tubes must be at equal radial distances.
  • Final adjustment of balance of tubes and bucket should be made on a rough balance by adding a few drops of water to the buckets. If balance of tubes and bucket is not maintained, motor of centrifuge may get damaged.
  • Centrifuge bowl should be kept clean and if a tube is accidentally broken, one should make it sure to clean the centrifuge before using it again.
  • The centrifuge machine should be operated with its cover or lid in place, otherwise it will reduce its speed.
  • Cotton-wool should never be used as a stopper for tubes during centrifugation.
  • Centrifuge must be started slowly and then the speed is increased.
Precautions:
    Tubes in centrifuge must be balanced properly. If it is not done so, tubes get broken.
    Do not increase or decrease the speed of the centrifuge too rapidly
    Do not touch the centrifuge when it is in operation.

Other Types of Centrifuge Machine :
Hand Centrifuge
Electric Centrifuge



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