CHAPTER TWO: LABORATORY TECHNIQUES AND SAFETY  
LABORATORY SAFETY MEASURES  
A laboratory is a special room or building used for doing scientific experiments.  
Chemistry laboratory is a special room where chemistry experiments are carried  
out.  
It is a special room where scientific experiments, research and analysis involving  
chemicals are conducted.  
Characteristics (qualities) of a good chemistry laboratory  
(i) Should have water, gas and electric supply  
(ii) Should have large windows for good ventilation and light  
(iii) Should have more than one door (exits) opening outward for easy exit in case of  
accidents of danger.  
(iv) Should have fume chamber for experiments which produces toxic gases  
(v) Should have a chemical store for keeping laboratory apparatus, chemicals and  
reagents  
(vi) Should have preparation room for technician to sit and design scientific  
experiments  
(vii) Should have drainage system for draining out (disposing off) dirty water.  
IMPORTANCE OF SCIENCE LABORATORIES TO STUDENTS  
➢
Science laboratories provide basic training.  
The training develops student’s skills necessary for more advanced study or  
research. Because experiments involve manipulation of materials of science.  
Enhance mastery of the subject matter.  
➢
Laboratory experiences may facilitate student understanding of specific scientific  
facts and concepts through performing experiments which finally prove or  
disprove the hypothesis.  
➢
➢
Helps the student to develop better memory power.  
There is always an active involvement of both hands and mind while  
experimenting (performing experiments).  
Developing practical skills.  
Experiments develop skills in using scientific equipments correctly and safely,  
making observations, taking measurements, and carrying out well-defined  
scientific procedures.  
➢
Cultivating interest in science and science subjects.  
As a result of laboratory experiences that make science “come alive,” students  
become interested about science and see it as relevant to everyday life.  
➢
Understanding of the nature of science.  
Laboratory experiences may help students to understand the values and  
assumptions inherent in the development and interpretation of scientific  
knowledge, such as the idea that science is a human endeavor that seeks to  
understand the material world and that scientific theories, models, and  
explanations change over time on the basis of new evidence.  
Developing teamwork abilities: Laboratory experiences may also promote a  
student’s ability to collaborate effectively with others in carrying out complex  
tasks, to share the work of the task, to assume different roles at different times,  
and to contribute and respond to ideas.  
➢
➢
Improving vocabulary:  
The terminology used in science classes are different from what one learns in  
normal classrooms. Through science experiments, kids learn about new concepts  
and words which expand their vocabulary.  
➢
Developing scientific reasoning: Laboratory experiences may promote a  
student’s ability to identify questions and concepts that guide scientific proof.  
LABORATORY SAFETY MEASURES  
Meaning: Laboratory safety measures are practices which put risks to a minimum  
level so as to minimize or eliminate injuries and exposure to harmful substances.  
OR Are practices, procedures and guidelines for protecting individuals working in the  
laboratory from injuries, accidents and exposure to hazardous substances.  
Importance of laboratory safety measures  
(i) Minimize or eliminate injuries  
(ii) Minimize or eliminate exposure to harmful substances  
(iii) Protect the environment from being exposed to harmful substances  
The following are some of the safety measures to be considered in the  
laboratory  
(i) The laboratory should be equipped with the working fire extinguishers fitted in  
accessible position.  
(ii) Laboratory floors should not be polished to avoid slippery  
(iii) Each laboratory should contain at least one first aid kit with all the necessary  
items.  
(iv) Stored chemicals should be inspected regularly to ensure no use of expired  
chemicals.  
(v) All apparatus should be checked regularly to ensure they are safe to use  
(vi) Wear appropriate protective clothing to minimize exposure to hazards.  
(vii) All chemicals containers should be well-labelled to prevent accidental use of  
wrong substances  
(viii) Refrigerators and freezers used in the laboratory should be labelled “For  
chemical use only”  
(ix) Chemicals which can easily react with each other should not be stored together  
(x) Cup boards, storage cabinets and drawers should have locks  
(xi) Emergency exits should be present and easy to access and use. Doors should  
open outward.  
(xii) Gas cylinders should be labelled, stored well and supported. They should be in  
good working condition all the time.  
(xiii) Fume chamber should be labelled. It should be kept in a good working  
conditions to minimize gas leakage.  
(xiv) There should be a manual or instructional guide on how to treat spills of  
different chemical substances.  
(xv) All laboratory users should wear appropriate clothing (protective gears) to  
minimize exposure to hazards.  
(xvi) Containers for chemicals should be checked regularly to ensure that they do not  
leak.  
(xvii) Equipment for monitoring accidents such as fire should be installed to give  
alerts of any possible dangers.  
(xviii) Any chemical spills should be cleaned immediately  
(xix) Flammable chemicals should never be heated over an open flame.  
(xx)  
Keep the doors and windows open during experiments  
(xxi) Never use broken apparatus  
HANDLING CHEMICALS SAFELY  
Chemicals in the laboratory are not always safe therefore; you must know their  
hazards by checking the safety signs labelled on their containers. All chemicals which  
are not correctly labelled should be removed from the laboratory and destroyed.  
CHEMICAL WARNING SIGNS (HAZARD SYMBOLS)  
Safety signs (warning signs) are symbols or words that warn for potential hazards  
or provide instructions for safe usage of the substance.  
Are safety and visual symbols or indicators used to alert personnel to potential  
hazards. They are found in restricted areas like laboratory.  
The following are some of the warning signs used in the laboratory and their meaning  
as shown in the table:  
(i) Toxic  
(ii) Irritant  
(iii) Flammable  
(iv) Oxidant (Oxidizing agent)  
(v) Corrosive  
(vi) Explosive  
(vii) Danger of electric shock  
(xi) Keep away from water  
(viii) Fragile  
(ix) Radioactive (x) Careful  
(xiii) Harmful  
(xii) Health hazard  
A. TOXIC  
Toxic symbol means that a substance is dangerous and can cause death within a  
short time. Toxic substances containing poisonous ingredients, Example of toxic  
substance is, mercury, barium chloride and cyanide.  
They should not be allowed to get into your body through mouth, nose, eyes or ears.  
The following precautions should be taken when handling toxic substances;  
•
If it happens that these substances touch your skin accidentally, wash it  
immediately with ample water.  
•
•
•
Never eat or drink when handling toxic substances.  
Wash your hands after using toxic substances.  
Put on personal protective equipments (PPE) such as gloves, laboratory coat and  
safety goggles.  
•
•
Use them in a well-ventilated room  
Do not mix toxic substances.  
B. HARMFUL  
Harmful symbol means that a substance is poisonous and can affect our health or  
make you fall sick for long time.  
They do not normally kill instantly but have detrimental effects following a long  
exposure to them. Example of harmful substance is alcohol, paint, insecticide and  
ammonia  
The following precautions should be taken when handling harmful  
substances;  
•
•
Never eat or drink when handling harmful substances.  
Wash your hands after using harmful substances.  
•
Put on personal protective equipments (PPE) such as gloves, laboratory coat and  
safety goggles.  
•
•
Use them in a well-ventilated room  
Handle the containers properly to avoid damaging them.  
C. IRRITANT  
Irritating substances cause pains or itching when in contact with the body.  
This substance can annoy parts of the body when in contact with the body surface for  
a long period of time. Example of irritant substances are very dilute acids.  
The following precautions should be taken when handling irritant  
substances;  
•
•
Prevent them from becoming in contact with your skin  
If it happens that these substances touch your skin accidentally, wash it  
immediately with ample water.  
•
•
•
•
Never eat or drink when handling irritant substances.  
Inspect the containers before handling  
Wash your hands after using irritant substances.  
Put on personal protective equipments (PPE) such as gloves, laboratory coat and  
safety goggles.  
•
Handle the containers properly to avoid damaging them.  
D. FLAMMABLE  
These are substances that can catch fire easily.  
Flammable substances can be set into fire by any kind of sparks, keep it away from  
welding or fire.  
Examples of flammable substances are methylated spirit, ether, acetone, kerosene,  
petrol, butane, hydrogen gas, ethanol and methanol.  
The following precautions should be taken when handling flammable  
substances;  
•
•
All burners must be put off.  
kept away from open flames or fires  
•
Put on personal protective equipments (PPE) such as gloves, laboratory coat and  
safety goggles.  
•
•
•
•
•
•
•
•
Use small amount of flammable substance.  
The containers used to carry them must be stoppered immediately after use.  
Avoid smoking.  
Never heat flammable liquids directly with a flame  
Never pour flammable liquids into the sink.  
Use them in a well-ventilated room  
Dispose flammable wastes materials properly.  
Handle the containers properly to avoid damaging them.  
E. OXIDIZING AGENT  
Oxidizing agent symbol means that the substance can speed up or stimulate the  
rate of burning. Oxidizing agents readily gives off oxygen.  
In the presence of oxidizing agent small fires can be made very big, therefore, they  
must be kept away from fires no matter how small that fire may be.  
For example potassium permanganate, potassium nitrate, oxygen gas, chlorine gas,  
fluorine gas and hydrogen peroxide  
The following precautions should be taken when handling oxidizing  
substances;  
•
•
•
kept away from open flames or fires  
Avoid smoking  
Put on personal protective equipments (PPE) such as gloves, laboratory coat and  
safety goggles  
•
•
•
•
Keep containers closed when not in use.  
Handle the containers safely to avoid damaging them.  
Keep them away from combustible materials.  
Store them in cool areas.  
F. CORROSIVE  
Corrosive substances refer to those chemicals that can burn or corrode surfaces as  
well as the human skin.  
They can also corrode wood or metals. You can become blind if such substances  
accidentally get into your eyes.  
Examples; Concentrated mineral acids such as sulphuric acid, hydrochloric acid and  
nitric acid, and concentrated alkalis such as sodium hydroxide, potassium hydroxide  
and ammonia.  
The following precautions should be taken when handling corrosive  
substances;  
•
•
Inspect the container before handling  
Put on personal protective equipments (PPE) such as gloves, laboratory coat and  
safety goggles.  
•
Prevent skin contact (if by accident come into contact with your skin go to the  
sink and wash with a lot of water).  
•
•
•
Avoid eating or drinking  
Keep containers closed when not in use.  
Wash your hands and skin after handling.  
G. RADIO ACTIVE  
Radioactive symbol means that the substance emits harmful radiations.  
This radiations when penetrate human body can cause damage.  
Examples of radioactive substances are uranium and plutonium  
Diagram  
The following precautions should be taken when handling radioactive  
substances;  
•
Put on personal protective equipments (PPE) such as gloves, laboratory coat and  
radiation shields.  
•
•
•
•
Avoid long exposure to radioactive substances.  
Avoid smoking  
Avoid eating or drinking.  
Never work alone  
H. FRAGILE  
Fragile symbol means that the substance can be easily broken or damaged.  
Therefore, should be handled with care to prevent them from breaking.  
Example of fragile substances are glass apparatus in the chemistry laboratory.  
The following precautions should be taken when handling fragile  
substances;  
•
•
Inspect them before using  
Put on personal protective equipments (PPE) such as shoes, gloves, laboratory  
coat, and safety goggle and face shields.  
•
•
•
•
•
•
Never hold fragile apparatus by its neck  
Never carry fragile apparatus by its side  
Use both hands when handling fragile apparatus.  
Never use hands directly to pick up broken glassware from the floor.  
Never place them near the edges of workbench  
After using wash them and store them properly in a right place.  
I. CAUTION  
Caution symbol means be carefully because a substance can cause damage to  
organs from a short-term exposure.  
J. EXPLOSIVE  
Explosive chemicals are those that explodes or blasts easily.  
Because the reaction is rapid, it results into throwing off particles at a high speed. For  
this reason, they should not be kept in glass containers because during explosion the  
particles will disperse around and cause serious injuries to people around.  
Precautions to be taken when handling explosive substances;  
•
•
kept away from open fires  
Put on personal protective equipments (PPE) such as gloves, laboratory coat, face  
shields or safety goggles.  
•
•
•
Avoid keeping them in glass containers.  
Avoid smoking  
Keep them in cool places  
K.  
KEEP AWAY FROM WATER  
Keep away from water symbol is the caution that advice you to keep item away  
from the water. For example computer, mobile phones, radio etc.  
L. HEALTH HAZARD  
This symbol means a substance is hazardous, can cause serious long-term health  
effects such as cancer, breathing difficulties and damaging organs.  
M. HAZARDOUS TO THE ENVIRONMMENT  
Indicates substances that are toxic to aquatic organisms or may cause long lasting  
environmental effects. They should be disposed off responsibly.  
NOTE;  
Warning or safety signs are better than words because signs are simple, easy to  
see and identify. These signs are used all over the world, so no matter what  
language they are using you will still understand the hazard.  
Other safety signs and their meaning are as follow:  
No entry  
Unsafe water  
Biohazard  
Exit  
No smoking  
Eye and face  
protection  
required  
Eye protection  
required  
Gas under pressure  
EXERCISE  
1. Imagine you have been given a chance to advise the school building committee on  
how should the laboratory building look like. What could be your advice?  
2. What dangers are likely to occur if a laboratory user fails to follow the laboratory  
safety measures?  
3. How can safety signs be used to prevent accidents and injuries in the laboratory?  
LABORATORY RULES  
Laboratory rules are statements which explain what to do or not to do in the  
laboratory.  
OR: Laboratory rules are the set of regulations governing practical activities, safety  
and order in the laboratory.  
Importance of laboratory rules  
Laboratory rules are important in order:  
(i) To have successful practical activities by obtaining accurate results  
(ii) To avoid hazards. Ensure safety in the laboratory  
(iii) Guides laboratory activities.  
Laboratories rules are divided into three parts, namely:  
(a) Before practical activities  
(b) During practical activities  
(c) After practical activities  
(a) Laboratory rules before practical activities  
(i) Do not enter in the laboratory without the permission or presence of the  
teacher or laboratory technicians.  
(ii) Keep the windows open for proper ventilation.  
(iii) Master the location of all exits.  
(iv) Dress properly for the laboratory activities. Wear laboratory coats and safety  
goggles. Do not wear loose or floppy clothing. Tie back long hair. Do not  
wear shorts, or walk barefoot or in sandals. Roll up long sleeves.  
(b) Laboratory rules during practical activities  
(i) Read instructions carefully before you start any activity.  
(ii) Do not eat, drink, play, run or smoke in the laboratory  
(iii) Do not taste or smell chemicals unless advised on how it should be done  
(iv) Do not spill liquids on the floor  
(v) Do not use dirty, cracked or broken apparatus  
(vi) Do not touch any electrical equipment with wet hands  
(vii) Turn off any gas or water taps that are not in use  
(viii) Do not remove any chemical or equipment from the laboratory without  
permission  
(ix) Keep inflammable substances away from open flames  
(x) Read the labels on chemical containers to be sure you have the right  
substance. Do not interchange labels  
(xi) Report any breakages or accidents to the teacher or laboratory assistant  
immediately  
(xii) Replace covers and stoppers on the containers after using the chemicals  
(xiii) Only perform the intended experiments. Do not set up your own  
experiments or interfere with someone’s experiment.  
(xiv) In case of a gas leakage turn off all the gas taps and open the windows.  
Leave the laboratory immediately.  
(xv) Use fume chamber when doing experiment which produces harmful gases  
and fumes  
(xvi) When heating substances do not point test tubes or burners towards  
yourself or other people  
(xvii) If you do not understand something, ask your teacher or the laboratory  
technician before proceeding  
(xviii) Use lighter or wooden splint to light burners. Do not use papers. Always  
strike the match before turning on the gas tap.  
(xix) Wash off any chemical spillage on your skin or clothes with plenty of water.  
(c) LABORATORY RULES AFTER PRACTICAL ACTIVITIES  
(i) Clean up the equipment and store them safely  
(ii) Turn off gas and water taps.  
(iii) Clean the working surfaces, benches and sinks  
(iv) Wash your hands with soap and running water.  
(v) Dispose of any wastes appropriately. Use the litter bins and not the sinks to  
dispose any solid waste.  
(vi) Do not pour concentrated chemicals into the sinks.  
(vii) Do not return unused chemicals to their original containers  
EXERCISE  
1. Why should chemicals in the laboratory be labelled and always well closed?  
2. You have been assigned by your chemistry teacher to present the benefits of  
having laboratory rules. Use the following rules to prepare your presentation:  
(a) Do not eat, drink, smoke, play or run in the laboratory  
(b) Do not taste or smell a chemical or anything unless you have been instructed  
on how to do it.  
(c) Use a fume chamber when carrying out experiments which produce harmful  
gases and vapours.  
(d) Perform the intended experiments only.  
3. Give reasons to support each of the following statements:  
(a) A laboratory should be equipped with working fire extinguishers  
(b) A laboratory should have large windows.  
(c) Concentrated chemicals should not be poured into sinks.  
FIRST AID AND FIRST AID KIT  
FIRST AID  
Definition: First aid is the help given to a sick or injured person before getting  
professional medical help.  
OR  
First Aid is the help given to injured or sick person before taking him or her to  
hospital  
OR  
First Aid is all that we can do to help an accident victim before we can get  
professional medical help in hospitals  
First Aider: First Aider is a person who is provides First Aid.  
Qualities of a good first aider  
A good first aider should have the following qualities  
(i) Should have knowledge of First Aid principles.  
(ii) Should be physically fit so that can perform First Aid tasks such as lifting  
(iii) Should have good communication skills so that can communicate clearly with  
injured person others  
(iv) Should have good discipline so that can follow First Aid principles.  
(v) Should be patient and tolerant.  
(vi) Should have confidence in decision making.  
(vii) Prompt and quick; as soon as an accident or injury occurs, the first aider should  
be prompt and quick, to render or provide assistance to the victim without delay.  
(viii) Leadership quality; a first aider should have the qualities of leadership like  
motivating, controlling and directing the other people, organizing things required  
for first aid and maintaining the situation effectively.  
Importance of first aid  
(i) It reduces pain and suffering.  
(ii) It reduces the likelihood of death (It saves life)  
(iii) It shortens recovery time  
(iv) It prevent permanent disability  
(v) It prevents the victim’s condition from getting worse  
(vi) It brings hopes and encouragement to victim.  
Precautions that should be taken when giving first aid to a victim of  
accident are:  
heck whether you or the casualty (victim) is in any danger.  
from any danger.  
r sneeze onto the casualty’s wounds.  
face shield, safety boots, and protective coat whenever necessary.  
POSSIBLE CAUSES OF ACCIDENTS IN THE LABORATORY ARE:  
(a) Spilled liquids left on the floor may cause slipping and falling.  
(b) Accidental swallowing of harmful chemicals  
(c) Poor ventilation may cause poisoning by inhaling harmful gases and fainting due  
to lack of oxygen.  
(d) Eating or drinking in the laboratory may cause food poisoning through  
contamination from harmful gases or chemicals.  
(e) Improper disposal of chemical wastes may result in explosions, burns or fire  
(f) Wrong use of apparatus /equipments results into breakage which can cause cuts.  
(g) Gas leaks from the taps or cylinders may lead to fires or even explosions  
(h) Failure to follow the right experimental procedures that can lead to explosions and  
damage of equipment  
(i) Use of wrong reagents due to wrong labeling or use of expired reagents may  
cause burning, poisoning or damage to equipment.  
(j) Chemical spills and exposure that can lead to burns and damage to body parts  
such as eyes and skin  
(k) Lack of adequate information on procedures and hazards related to certain  
practical activities or reactants may result in burns and explosions.  
(l) Electric shock can occur if electrical appliances are not plugged properly or are  
touched with wet hands.  
The table below summarizes some of the accidents common in chemistry  
laboratory, causes and preventive measures to be taken.  
ACCIDENT  
Fire and  
CAUSES  
PREVENTIVE MEASURES  
▪
Failure to follow the right  
procedure for the  
experiment  
▪
▪
▪
Follow right procedure for  
experiments  
Explosion  
Ensure proper disposal of  
chemical waste  
▪
▪
▪
Improper disposal of  
chemical wastes  
Gas leakage from the taps  
or cylinder  
Make sure that gas cylinders  
and taps are properly  
closed.  
Leaving containers for  
▪
Make sure all flammable  
materials are properly  
sealed and stored.  
flammable chemicals  
un-stoppered.  
Burns  
▪
▪
Handling hot items  
without the proper tools  
Handling corrosive  
▪
▪
Proper use apparatus when  
handling hot objects  
use of personal protective  
substances with bare  
hands  
Chemical spills  
equipments like gloves and  
laboratory coat when  
dealing with corrosives  
Clean all chemical spills  
Proper disposal of chemical  
waste  
▪
▪
Improper disposal of  
chemical wastes  
Use of wrong reagents  
▪
▪
▪
▪
Use correct reagents for  
the experiment.  
▪
▪
Use of sharp tools  
Use of broken glass  
materials  
Cuts and  
scrapes  
▪
▪
▪
Handle sharp tools with  
great care  
Never use broken  
apparatus.  
▪
Failure to follow  
procedures and  
laboratory rules  
Wash your hands before  
and after using chemicals  
and protect your clothing  
and skin with laboratory  
coat and gloves.  
Contamination  
Headache and  
nausea  
▪
Inhalation of harmful  
gases and chemicals due  
to poor ventilation  
▪
▪
▪
having fume chambers  
Using ventilation fans.  
Opening windows during  
experiment  
▪
Carelessness,  
Spills and  
breakage  
▪
Be careful when performing  
experiments or when  
moving through each step  
in the laboratory  
Failure to follow procedures  
▪
Rushing.  
▪
▪
Poor ventilation  
Eating or drinking in the  
laboratory  
Poisoning and  
fainting  
▪
Ensure you follow proper  
procedures for ventilation.  
Slipping and  
Falling  
▪
▪
Spilled liquids left on the  
floor  
▪
▪
Clean all spilled liquids  
immediately  
Slippery floor  
Laboratory floor should not  
be slippery  
Electric shock  
▪
Appliances are not  
plugged properly.  
Touching electrical  
appliances with wet  
hands  
▪
▪
Appliances are not plugged  
properly.  
▪
Don’t touch electrical  
appliances with wet hands.