Revision KNEC questions and Answers on Laboratory Equipments

Carry microscopes using both hands by the limb and the base and should be in upright position to avoid dropping loose parts e.g. mirror and eye- pieces.
Do not touch the microscopes lens using fingers
Clean microscope lens using lens cleansing tissues
Microscopes should be kept clean and covered to avoid dust
Keep microscopes away from direct sunlight and dust i.e. always cover microscopes and keep then in locked cupboards
The optical parts should be cleaned using a little xylene on a lens cleaning tissue or soft cloth. Do not use sleeves or lab coats
Never place microscopes at the edge of benches
Avoid using a high power objective when a low power objective is satisfactory
It is dangerous to rock down the objective while you are looking into the microscope. You risk breaking the slide, the objective lens or the condenser
Repair should be left only to a trained expert
Do not place wet preparation on the stage without wiping the undersurface of the slide

Discuss any four basic requirements that must be considered for installation of weighing balance

The correct positioning of balances depends a lot on the condition of the balance room itself. The balance room should have the following requirements

Proximity – the balance room should be positioned in a central location for easy access by many people
External environment– the balance room should not be situated on the outside wall of the laboratory.

This is in order to avoid drought and fluctuation in temperature. It should have only one door opening into it and ventilation should be by means of air conditioners and not windows
1. Vibration – the balance room should not be situated near any source of vibration such as moving machinery, passing traffic or movement of persons near the vicinity of the apparatus
2. Door– the door to the balance room should be fitted with a spring to avoid vibration when it is slammed or banged humidity is 50oc and the temperature is 25 ^oc . Constant temperature is very important in order to prevent expansion of internal parts of the balance.

Balance rooms should always be kept clean and the floor should be mopped and not swept, all the corners between the floor and the walls should be covered to prevent accumulation of dust.

Effects of vibration on a balance

Vibration makes accurate reading on the balance to be impossible. It also reduces the life span of the balance by causing excessive wear on the internal parts i.e. the knife-edge. Moving machinery, traffic, people etc. cause vibration.
The basic method of overcoming vibration is by interposing a number of dissimilar materials between the balance support and the source of vibration. The materials used must be stable .if the amount of vibration is small; the balance should be placed on a rubber stopper and supported on a wooden support.

Describe how to calibrate an analytical balance

Calibration is performed by placing a known weight on the balance pan and adjusting the circuitry to indicate the mass of the calibrating weight.

List four extraneous forces which can affect accuracy of analytical balance
Temperature

The slightest change in room temperature can cause noticeable changes in the weight of the sample. Strict temperature controls are therefore needed to give accurate readings on the analytical balance.

Vibrations

Vibrations from refrigerators, ventilation systems, and other equipment that produce vibrations can affect the precision of an analytical balance. Since the sample size is really small, the slightest vibration can rearrange, displace, or spill the sample, thereby affecting the amount of material available for measuring as well as its distribution in the balance. Small vibrations can also disrupt the delicate machinery of the analytical balance. These disruptions may require recalibration of the analytical balance, which can mean lost time and money from pertinent research efforts.

Chemical Reactions

Samples can also be very sensitive to slight atmospheric changes in temperature and wind pressure. For instance, if you expose a piece of white phosphorous to open air, it will burst into flames. Exposure of such volatile samples to those conditions can lead to chemical reactions that are not only dangerous but can also alter the state of the sample. That is why users should take precautions to ensure that the sample remains chemically inert during the weighing process.

Air Currents

Air currents can affect the intricate mechanisms of the analytical balance the same as temperature and vibrations can alter the measurement of a small sample size. Changes in air pressure from ceiling fans, air conditioners, and open doors can also cause sensitive equipment to show wrong measurements.

Calibration

Calibrating an analytical balance will ensure that it gives an accurate reading. It is recommended that users test their balances every few months to ensure that the calibration settings are still accurate.

User Error

In most cases, faulty measurements are as a result of user error. A lab worker may accidentally leave a sample on the table, exposing it to reactions with atmospheric elements; or a lab worker may improperly calibrate the machine which can affect the accuracy of the balance. That is why most labs have strict procedures for maintaining atmospheric standards to ensure accurate readings and lower instances of user error.

Cluttered Work Space

The accuracy of analytical balances depends on how clean the work space is. A cluttered work space will impact the accuracy of results. Ensure that nothing comes in contact with the analytical balance. If anything touches or rubs against the balance, it will cause discrepancies in the readings.

Magnets

Some balances use magnets as a part of the weighing system. Therefore, placing the balance near magnetic equipment or weighing magnetic sample can result in erroneous readings.

Slope

The scale or balance must be placed on a level surface. Precision balance scales weigh the materials assuming that the load is applied parallel to the force of gravity and perpendicular to the weighing platform.

Improper Grounding

Make sure that the AC source is properly grounded to prevent the build-up of static energy. Secondly, ensure that the chassis is grounded to avoid electrostatic discharge.

Plastic or Glass Weigh Containers

Unlike metal containers, plastic and glass weigh containers can hold an electric current. Static charges can result in non-repeatable measurements or drifting measurement readings. Even an accurate weight scale can provide incorrect readings in such cases.

Not handling the sample appropriately

Lab workers need to handle the samples with care. For instance, hot or warm samples should be cooled first. Hygroscopic samples need to be weighed quickly with the balance doors closed to avoid absorption of moisture. Not following these steps will affect the measurements. Place the sample in the center of the balance for the most accurate results.

Describe

Outline how to prepare analytical balance before use
Before weighing anything on the analytical balance you must make sure that it is leveled and zeroed.
To check the leveling on the balance, look at the leveling bubble on the floor of the weighing chamber. If it is not centered, center it by turning the leveling screws on the bottom toward the back of the balance.
Once the balance is leveled, close all the chamber doors and press the control bar on the front of the balance. After a few seconds, a row of zeros will appear. This indicates that the balance is zeroed and ready for use.

Weighing a liquid, powder, or granular substance

These substances must always be weighed using an appropriate weighing container.
Place the weighing container on the balance pan and close the doors.
Tare the container by briefly pressing the control bar. The readout will read zero with the container sitting on the pan. This allows the mass of your sample to be read directly.
Add the substance to be weighed. Be careful not to spill chemicals on the balance. If need be, you can remove the container from the weighing chamber while you add the sample provided that noone presses the control bar before you weigh your sample.
With the sample and its container sitting on the pan, close the chamber doors and read the display to find the mass of your sample.

Weighing a solid object directly on the balance

If the object you need to weigh is a solid object, you can weigh it directly on the pan. Be sure the balance is zeroed. Open the chamber doors, carefully place the object on the balance pan, close the doors, and read the mass of your object.

Cleaning up and shutting down the balance

When you are done with the balance, make sure you have properly cleaned up any chemicals that may have spilled on the balance. At the end of the day, the balance can be turned off by lifting up gently on the control bar.

Outline the process of cleaning the jet of a bunsen burner

Clear any blockage in the jet using a stove pin or a piece of wire.
1. Clean off any encrusted deposits using a fine grade sand paper or emery cloth.
2. c) Wash the jet in water or use a little dilute hydrochloric acid for heavy stains or persistent coatings. Sealants may be removed with propanone (acetone).
Setting of weights in a triple beam balance to measure 399.3g.
Clean the balance pan and zero all three weights by moving them to the left end of their respective bars. The indicator pointer should be at the center line of the scale. If not, adjust it by turning the screw weight until the pointer is centered at zero.
If a set of calibration weights is available, place one or more on the center of the pan and use the following procedure to determine the weight indicated by the scale. This should be within a tenth of a gram of the combined weights of the standards. Remove standard weights from the pan.
Be sure the object to be weighted is free of extraneous materials and place in center of balance pan.
Move the heaviest (backmost) weight to the right until the indicator pointer moves above the center line of the scale. Then move it back one notch being careful that is is located in one of the notches on its bar.
Repeat this process with the weight on the middle bar – again being certain it is in a notch when in its final position.
Slide the weight on the third (frontmost) bar to a point that causes the indicator to move above the center line. Then move it back in the opposite direction until the indicator pointer comes to rest on the center line of the scale.
Add the indicated weights of all three scales to obtain the weight of the sample.

(c ) The weight tarring procedure in a triple beam balance

Tarring a triple beam balance means weighing the empty container so that its weight can be deducted from the weight of the sample you want to weigh.
In order to tare ,do the following:
Weigh the empty container
Add to the container’s weight the weight of the substance you wish to measure.
Set the weights on the balance to this calculated total expected weight.
Add the substance in small increments into the weighing container on the balance until the balance “balances.”

State any four-maintenance practice for an analytical balance

The balance should be kept clean at all times
Chemicals and dust should be wiped away with a soft cloth
Always cover the balance
Do not apply lubricants to the knife edges or bearings
Servicing must be carried out by experts only

Describe how the PH meter electrodes work

pH electrodes Have a glass bulb or bubble that was filled with strong electrolyte..
The majority of today’s pH electrode types are known as combination electrodes. Combination electrodes have the glass Hydrogen Ion (H+) sensitive electrode and an additional reference electrode all in one housing.

The combination or pH electrode measures the difference in potentials between the two sides in the glass electrode. To measure the potentials it must be a closed circuit. The circuit is closed through the internal solutions of the electrode and the external solution that is being measured and the pH meter.
As the electrode is immersed in the test solution the glass bulb senses the hydrogen ions as a millivolts (mV) due to the positive charge of the hydrogen ions. The electrolyte or internal solution picks up the mV signal from the glass bulb. That signal is then passed to the internal electrode. The Ag/AgCl wire then passes that signal to the electrode cable that leads to the meter.
The reference electrode containing electrolyte or filling solution generates a constant mV, which is transferred to the Ag/AgCl wire. The wire then passes the signal, which can be considered a “control” being measured to the electrode’s cable.
The circuit is closed by a minute amount of internal solution from the reference electrode flowing through a porous membrane made of a ceramic wick. This membrane or junction as it is called is located the electrode body.
The pH meter measures the difference between the internal electrode and the reference electrode in millivolts DC. This mV reading is then read by the meter and is displayed in pH units.

Outline the regular maintenance of a PH meter electrodes

Always keep your pH electrode moist. We recommend that you store your electrode in a solution of 4 M KCl. If 4 M KCl is not available, use a pH 4 or 7 buffer solution.
DO NOT store electrode in distilled or deionized water—this will cause ions to leach out of the glass bulb and render your electrode useless.

Describe the positioning of the PH meter on a laboratory bench

Avoid placing a PH meter at the edge of the bench , place it inside a beaker having water .
Avoid temperature fluctuations and never keep the pH meter exposed to direct sunlight.
The glass electrode should not be left out of the storage solution for prolonged intervals as the glass membrane gets dehydrated resulting in slower response and can eventually lead to complete response failure.

Define the term ‘indicator’ as used in the laboratory

Indicators are generally organic compounds, which changes color according to the PH of the solution in which they are dissolved .They give a characteristic color change that visually indicate the end point or at neutralization point. Indicators work over some range of PH, usually between 2-3 units. This therefore means that a different indicator must be used for a specific PH range that is being examined

State two characteristics of a good indicator

Should give a characteristic color change in an acid or base solution
Should give a characteristic sharp color change at the end point of neutralization reaction
Should be non-toxic
Should be easily available and cheap

Describe four consideration in installation of mercury barometer

The installation board for a mercury barometer is strong, and vibration should not be transmitted easily.
A change of room temperature is slow and uniform.
A sliding door is good in order to avoid the pressure change by opening and closing of a door.
The standard of electric barometer is set near the mercury barometer.
Align the tip of a ivory pointer with the height of the internal sensor of the electric barometer.
As for reading of mercury barometer, it is desirable for the expert person to carry out.
The reading value of mercury barometer requires the corrections for temperature and for gravity.

Outline proper positioning of water still in the laboratory

Proper positioning of a water still in the laboratory is important to ensure safe and efficient operation. Here are some guidelines for positioning a water still:

Stable Surface: Place the water still on a stable and level surface. This helps prevent accidental tipping or movement during operation.
Adequate Ventilation: Ensure that the water still is positioned in an area with adequate ventilation. This is important as water stills produce heat and release steam during operation. Adequate ventilation helps dissipate heat and allows for the removal of steam and any volatile gases that may be released.
Access to Water and Power: Position the water still close to a water source and a power outlet. This allows for easy connection to the water supply and electrical power needed for operation.
Clearance Space: Provide sufficient clearance space around the water still. This ensures easy access for maintenance, cleaning, and any necessary repairs. It also allows for proper airflow and heat dissipation.
Distance from Flammable Materials: Keep the water still away from flammable materials or substances. This is important as water stills use heat sources for operation, and there is a potential risk of fire. Maintaining a safe distance from flammable materials minimizes the risk of accidents or fires.
Adequate Lighting: Ensure that the area around the water still is well-lit. Good lighting helps with visibility during operation, maintenance, and troubleshooting.
Accessible Controls and Gauges: Position the water still in a way that allows easy access to controls, gauges, and indicators. This facilitates monitoring and adjustments during operation.
Consider Workflow and Ergonomics: If the water still is used as part of a larger laboratory setup, consider the workflow and ergonomics of the space. Position it in a way that allows for efficient workflow and minimizes the need for unnecessary movement or strain.

It is important to consult the manufacturer’s instructions and follow any specific guidelines provided for the positioning and installation of the water still.

Explain how the following equipment may be maintained in the laboratory
1. Laboratory water still

Read and follow the manufacturer’s instructions carefully.
Ensure there is a sufficient supply of cool running water to feed the condenser.
Do not allow the boiler to run dry
Collect the distillate in a clean plastic or glass.
Avoid storing the distillate in for more than few days, always keep the container capped.
Clean regularly the still, descale it in case you always hard water.

NB: When buying a still, select one that can be easily cleaned without being dismantled.

PH meter
- Remove the detector electrode from the storage buffer solution.
- Rinse the detector electrode abundantly with distilled water.
- Remove the upper cover of the detector electrode.
- Fill the conduit surrounding the internal electrode with a saturated potassium chloride (KCI) solution. Use the syringe or applicator supplied with the KCI solution.
- Verify that the tip of the syringe does not touch the inside of the electrode.
- Close the electrode with its cover. Rinse the electrode in distilled water.
- Keep the electrode in storage buffer solution while not in use.
Microscopes
- Carry microscopes using both hands by the limb and the base and should be in upright position to avoid dropping loose parts e.g. mirror and eye- pieces.
- Do not touch the microscopes lens using fingers
- Clean microscope lens using lens cleansing tissues
- Microscopes should be kept clean and covered to avoid dust

Keep microscopes away from direct sunlight and dust i.e. always cover microscopes and keep then in locked cupboards
The optical parts should be cleaned using a little xylene on a lens cleaning tissue or soft cloth. Do not use sleeves or lab coats
Never place microscopes at the edge of benches
Avoid using a high power objective when a low power objective is satisfactory
It is dangerous to rock down the objective while you are looking into the microscope. You risk breaking the slide, the objective lens or the condenser
Repair should be left only to a trained expert
Do not place wet preparation on the stage without wiping the undersurface of the slide

Describe how to view a slide on a compound microscope

Turn the revolving turret (2) so that the lowest power objective lens (eg. 4x) is clicked into position.
Place the microscope slide on the stage (6) and fasten it with the stage clips.
Look at the objective lens (3) and the stage from the side and turn the focus knob (4) so the stage moves upward. Move it up as far as it will go without letting the objective touch the coverslip.
Look through the eyepiece (1) and move the focus knob until the image comes into focus.
Adjust the condenser (7) and light intensity for the greatest amount of light.
Move the microscope slide around until the sample is in the centre of the field of view (what you see).
Use the focus knob (4) to place the sample into focus and readjust the condenser (7) and light intensity for the clearest image (with low power objectives you might need to reduce the light intensity or shut the condenser).
When you have a clear image of your sample with the lowest power objective, you can change to the next objective lenses. You might need to readjust the sample into focus and/or readjust the condenser and light intensity. If you cannot focus on your specimen, repeat steps 3 through 5 with the higher power objective lens in place. Do not let the objective lens touch the slide!
When finished, lower the stage, click the low power lens into position and remove the slide.

(a) Explain three effects of vibrations on laboratory equipment

Vibration can accelerate machine wear,
consume excess power,
cause equipment to be taken out of service, resulting in unplanned downtime.
Other effects of vibration include safety issues and diminished working conditions.
Vibration makes accurate reading on the balance to be impossible.
It also reduces the life span of the balance by causing excessive wear on the internal parts i.e. the knife-edge.
Explain three ways of overcoming vibration in laboratory

The basic method of overcoming vibration is by interposing a number of dissimilar materials between the balance support and the source of vibration. The materials used must be stable. if the amount of vibration is small; the balance should be placed on a rubber stopper and supported on a wooden support.

Balances
- The balance should be kept clean at all times
- Chemicals and dust should be wiped away with a soft cloth
- Always cover the balance
- Do not apply lubricants to the knife edges or bearings
- Servicing must be carried out by experts only
Describe any four components of a centrifuge

Centrifuge consists of the following basic components:

Central shaft spindle, which rotates at high speed
Head fixed to a shaft with its arms holding to buckets
Mechanisms for rotating the spindle, which could be either manual rotating handle or electrical motor

Describe any four-maintenance practice for autoclaves
- Follow the manufacturer’s instructions
- Always fill the autoclave with the correct volume of water. Irreparable damage may occur if the autoclave boils when it is dry.
- Do not use saltwater as these enhances rusting of the autoclave
- Lubricate the screw clamps with oil
- Clean the autoclave immediately after use
- Servicing must be carried out by experts only
Explain the principle of centrifugation of a laboratory centrifuge

Centrifugation is a technique that helps to separate mixtures by applying centrifugal force. A centrifuge is a device, generally driven by an electric motor, that puts an object, e.g., a rotor, in a rotational movement around a fixed axis.

A centrifuge works by using the principle of sedimentation: Under the influence of gravitational force (g-force), substances separate according to their density.

State four functions of hot air oven

It is used to dry glassware,
sterilize items and general instruments,
For packaging items in life science, microbiology laboratory.
It is also used in chemical and pharmaceutical industries, food and beverage industries, textile industries.

List four causes of failure of spectrographic equipment to power on

Aging Equipment

aging equipment is the leading cause of equipment failure,

Assets that consistently run year after year require more frequent repairs over time.

. Operator Error

Another common cause of equipment failure is operator error. , it’s not unheard of for workers to occasionally work on unfamiliar machines when filling in for others.

Not only could the worker’s lack of specialized knowledge result in an equipment breakdown, but it could also cause an accident. Further, it could breach OSHA’s operator training requirements,

(c ). Lack of Preventive Maintenance

Lack of proper preventive maintenance programs can accelerate equipment failure and depreciating performance.

Over-Maintenance

performing too much maintenance can also be detrimental.

Outline the process of how colorimeters are used.

Switch on the colorimeter and let it warm for a duration that has been recommended by the manufacturer. These is important for optimum performance of filters and light detectors
Set the wavelength to the correct wavelength or simply insert the correct filter for the substance to be tested
Arrange the blank , standard and the test solution in the test tube rack
Clean the cuvettes using soft material e.g. Lens cleansing tissue or cotton gauze to avoid scratching them. Do not touch the sides of the cuvettes with fingers. instead hold them by the ground sides or sides which do not face the direction of light
Transfer the blank solution into the cuvette and place it into the cuvette chamber with its aides facing the light path. close the cuvette chamber and set the absorption to zero
Remove the cuvette from the chamber , pour the blank solution back into the test tube then pour the standard solution into the cuvette and record the absorbency
Repeat with the test solution and also record the absorbency
Rinse the cuvette with distilled water , drain off and wipe with the sort material and store carefully in small boxes to avoid scratches and dust
Calculate the concentration of the test solution as :

Conc. of test sol = abs of test sol X conc. std sol

Absorbency of standard sol

Explain how to clean cuvettes

Clean the cuvettes using soft material e.g. Lens cleansing tissue or cotton gauze to avoid scratching them. Do not touch the sides of the cuvettes with fingers. Instead, hold them by the groundsides or sides that do not face the direction of light

States the components of a colorimeter

The light source consisting of ordinary bulb
The filter used to produce monochromatic light
Wavelength selector
Cuvettes to hold the colored solution being investigate
Galvanometer and absorptiometry.

Describe the maintenance practice for a refrigerator

The inside should be kept clean and dry.
Avoid placing hot things in a refrigerator .Let them cool first.
Avoid packing things tightly into the refrigerator because they interfere with free air circulation.
Defrost the deep freezer region to prevent building up of mountains of ice which often breaks the delicate part of the refrigerator.
Keep the doors of the refrigerators closed except when putting or removing materials from it. Frequent or prolonged opening of the refrigerator doors interferes with internal temperatures.
Repair and servicing should be done regularly and by experts only.

Name two types of water deionizers
1. Cation- exchange resin
2. Anion- exchange resin.
Distinguish between an oven and an incubator explaining their use and operation mechanisms

Incubators are special ovens used to provide optimum conditions for growth of living things. Its construction is finer than that of oven. The inside is lagged with special materials, which serves as insulators. The temperatures inside it can be maintained between 0 – 80 ^oc with an accuracy of + or – 0.1^o
Incubators are electrically operated and have thermostats, which regulate and control the temperatures inside.
Ovens are used for drying, sterilization and baking. The temperatures inside range from 0- 250 ^o they normally made of two walls lagged with glass wool. They also have thermostats, which control the temperatures and uses mercury thermometers. They also have other accessories like ventilators to remove moisture, shelves etc.

Discuss the water distillation process using a water still.

Impure water is boiled and steam produced is condensed on a cold surface (condenser) to give chemically pure distilled water from which volatile organic and inorganic matter are removed .

Describe components of an autoclave

Autoclave chamber – these is made of a heavy cast metal

Tightly fitting lid with clamps and rubber seals
Metal packing drum which fits inside the autoclave chamber
Pressure valve set to open at the desired pressure.
Safety valve through which steam may escape if the pressure inside the autoclave exceeds a set safety value
Pressure gauge indicating internal pressure
Temperature gauge indicating the temperature of the steam
The air outlet used to vent air outside while heating and to also introduce air after sterilization
A built in heating and water cooling system
Replaceable rubber seal

.Describe sterilization using an autoclave

Caps of containers to be sterilized should be loosen, other items should be wrapped in porous brown paper and their edges carefully secured with autoclave tapes
Place the containers and other items in a wire basket or in the autoclave drum.
Pour distilled water or tap water into the autoclave drum to the level indicated by the manufacturer.
Place the basket or drum containing the items to be sterilized in the autoclave.
Close the lid and screw the lid clamps firmly and connect the horse to the air outlet.
Switch on the autoclave electric or gas plug or place it on a suitable heat source e.g. charcoal jiko.
As the water boils, a mixture of air and steam escape through the air outlet. Leave it to escape for about 5min.
Test if all the air has been expelled out by placing the other end of the horse inside a water bucket. the presence of air is indicated by bubbles , pure steam produce cracking sound as it condense into water
When all air have been expelled , close the air outlet and watch the pressure and temperature gauge .when pressure reaches 15 psc , reduce the heat and leave it for the recommended sterilization time using a timer clock
Turn off the heat and wait until the pressure gauge reach zero, open the outlet then open the lid and unpack.
Some autoclaves have indicator strips on the autoclave tapes, which changes color after sterilization.

NB: indicator strips are sometimes not reliable.

Describe the maintenance practice for a refrigerator

The inside should be kept clean and dry.
Avoid placing hot things in a refrigerator.Let them cool first.
Avoid packing things tightly into the refrigerator because they interfere with free air circulation.
Defrost the deep freezer region to prevent building up of mountains of ice, which often breaks the delicate part of the refrigerator.
Keep the doors of the refrigerators closed except when putting or removing materials from it. Frequent or prolonged opening of the refrigerator doors interferes with internal temperatures.
Repair and servicing should be done regularly and by experts only.

State the effects of the following on analytical balance

(a)Dust

Dust will cause an error in weight measurement obtained, it will also interfere with the operation mechanism of the balance. Dust which may lodge between the coil and the permanent magnet of the servomotor

High temperature

Samples that are too hot will set up convection currents and the apparent sample weight will be incorrect.

Describe cleaning of water bath in the laboratory.

Water Baths should be cleaned with a very mild household or laboratory detergent using a sponge or soft cloth.
Never use scouring powders, steel wool, or other abrasive pads.
Metal buildup can be removed using a mild household de-scaler and soft brush.
Rinse thoroughly after cleaning and be sure to dry the bath.

. Describe the cleaning of laboratory refrigerator.

Unplug Your Refrigeration Units
To eliminate the possibility of electrocution, the first thing you should do is unplug your refrigerator or freezer.
Empty Each Shelf of All Items
The second step should be to remove all of the products in your fridge or freezer. Make sure to actually remove the containers, don’t just move them to the other side of the fridge.
Throw Away Any Expired or Moldy Food
Perishables can easily get lost in the mix by being pushed to the back or concealed behind other items in a large refrigerator..
Completely Wipe Down the Interior of the Refrigerator or Freezer
Get a bucket with warm, soapy water and your choice of sponge to thoroughly clean your commercial fridge or freezer. Highly absorbent microfiber cloths and mitts are perfect for scrubbing down every inch inside your fridge and removing messes that have accumulated since the last cleaning.
Disinfect with a Sanitizer

Bacteria and mold can accumulate in a fridge over time, so it’s important to disinfect surfaces with a sanitizer. Be sure to use a safe sanitizer, as you’ll eventually be placing items back into the refrigeration units.

Vacuum the Condenser and Coils

Dust and debris saps the power being generated in your refrigeration unit’s condenser and refrigeration coils by clogging air intake. Over time, dust and debris can collect on your refrigerator, which can end up clogging the air intake. As a result, your condenser and refrigerator coils will need to use more energy to take in air and keep your refrigerator cool, resulting in a less-efficient fridge and a higher utility bill.

Clean Underneath and On Top of the Refrigerator or Freezer
Keeping the area around your refrigeration units clean can be just as important as cleaning the units themselves. Thoroughly mop the floor under and around the fridge or freezer.

List any four heating equipment in the laboratory

The common heating devices used in labs are bunsen burners, hot air ovens, hot plates, heating mantles, muffle furnaces, hot oil baths and microwave digestion systems.

Describe the maintenance practice for a biological safety cabinet

The installation, certification, decontamination and maintenance of BSCs must be performed by certified professionals upon installation and after relocation

If a cabinet has been used for research involving potentially infectious agents or human-sourced material, it must be decontaminated by an accredited professional prior to repairs, relocation or disposal.

To prepare your BSC for maintenance, certification or repair:

Empty the BSC of all items.

The cabinet must be completely cleared of any equipment, pipettes, waste, liquids and tubing.

Decontaminate the surfaces of the BSC with an appropriate disinfectant, such as a 10% bleach solution followed by 70% ethanol solution.

Draw a labeled diagram of a Bunsen burner.

Outline the process of cleaning the jet of a Bunsen burner.

Bunsen burners may become clogged with debris and will not function as effectively. Regular maintenance of a Bunsen burner must include cleaning blockages to ensure it stays in good working order.
Check the Bunsen burner nozzle for dirt, fluff or other debris. Clean the nozzle with a cotton swab and a non-corrosive solvent.
Check the air inlet holes. If there is any debris blocking the free-flow of air, clean with a cotton swan and non-corrosive solvent.
Clear blocked jets by pushing a piece of stiff wire through the jet.
Examine the mixing tube. If it is clogged with debris, remove it by twisting. If the mixing tube is jammed, use a spanner or adjustable wrench to work it loose. Clean the tube with warm, soapy water and a test tube brush. Ensure that the tube is completely free of residue by rinsing with clean water.

Explain how Regeneration deionizers work

Regeneration is a process that takes ion exchange resin beads that are exhausted (fully loaded), and removes ions that have been picked up during the in-service cycle so the resin can continue to be used. An ion exchange system consists of a bed of resin beads with the ability to pick up hardness or other elements by ion exchange. The resin beads can then be regenerated by a high concentration (10% brine) of salt or other regenerant chemical to restore the resin’s capacity, enabling the system to be used over and over for many years.
Regeneration of an ion exchange resin bed involves multiple processes, including:

Backwash

Chemical injection

Slow rinse

Fast rinse

The first step in regeneration is to backwash the system by running water backwards through the bottom of the bed. This lifts the bed and dislodges dirt, debris and other insoluble material that is in the bed. It also helps to remove air pockets in the resin bed and reclassifies the resin. Backwash is essential to minimize pressure drop and ensure even flow in the bed. Regular backwash is only carried out in co-flow systems. In counter-flow systems, backwash is done only when required.
The bed is then settled and regenerated with a brine solution or other regenerant chemical. This step drives off the hardness or other ions and restores the resin back to the required starting form for beginning a new service cycle.

After regeneration, the slow rinse step continues to push regenerant through the bed to continue conversion and remove the regenerant from the system. The fast rinse is a final rinse with raw water to ensure that water quality is being met after regeneration. In counter-flow systems, there can be a recycle step as an alternative to the fast rinse. Recycling between cation resin and anion resin will remove any remaining regenerant chemical.

After rinsing, the resin bed is returned to service. The total time to regenerate is < 2 hours and the total water used is about 7 x the resin volume: 15L bed = 105L (50 gal./ft³). The wastewater is discharged.
When a resin system regenerates, only about 60% – 80% of the total ion exchange resin capacity is restored. Some hardness or elemental ions are left on and in the resin. When next in service, some of these residual compounds will leach off the resin and pass into the effluent, and this is called “leakage.”

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