مهدي 63
2nd November 2011, 12:58 PM
Chemical Grades
Below is a list of chemical grades in order of purity, from highest to lowest.
ACS
Highest quality; often equals or exceeds the latest purity standards set by the American Chemical Society (ACS). This is the only universally accepted standard. Chemicals are of the highest purity attainable.
Reagent
Purity is generally equal to ACS grade. This grade is suitable for analytical work and is more than adequate for general lab use.
USP
A grade of sufficient purity to pass certain tests prescribed by the US Pharmacopoeia (USP); acceptable for drug use. USP grade may be used for most laboratory purposes.
NF
A grade of sufficient purity to meet the standards of the National Formulary (NF).
Lab
An upper-level intermediate quality. Exact impurities may not be known; however, lab grade is usually pure enough for most educational laboratories.
Pure
Purified, pure, or practical grade; a lower-level intermediate quality. Although this grade does contain impurities, it is usually pure enough for use in educational laboratories.
Technical
A good-quality grade used industrially. Use caution when substituting for reagent-grade or lab-grade chemicals.
When making a solution, one must first decide what degree of chemical purity is needed. Many types of chemicals are available in several grades of purity. Most of the chemicals listed in our catalog belong to one of the following 3 categories, in order from least pure to most pure.
Laboratory
Reagent
ACS
Choose the most appropriate grade based on need and cost. Lab-grade chemicals, because of their low cost and good chemical purity, find wide use in educational applications, such as teaching laboratories at both the secondary school and college levels. Reagent-grade chemicals are typically ACS-grade chemicals that have been repackaged and have therefore lost their ACS certification.
Carolina also offers a choice of packaging for a limited number of chemicals. Corrosive chemicals, such as concentrated acids, are normally packaged in glass bottles. For safety and convenience, our customers may order these chemicals packaged in plastic-coated safety bottles. A plastic-coated safety bottle will not shatter when dropped, which helps to contain the spill and simplify cleanup. Look at the item descriptions in the chemical section of the catalog for those chemicals available in plastic-coated safety bottles.
For safety purposes, read a chemical’s label twice before use. Read the label first when you take the chemical off the shelf and again before you remove any chemical from the bottle. When preparing solutions using concentrated chemicals, slowly add the more concentrated solution (e.g., sulfuric acid) to the less concentrated one (e.g., water). The reverse procedure can cause the solution to boil and spatter
Chemical Storage
Safety in the science classroom includes the storage of chemicals. WHMIS regulations under the Hazardous Products Act govern storage and handling practices of chemicals in school laboratories.
Key items to remember:
Chemicals should be stored in a safe location according to Chemical Class, not just alphabetically.
Appropriate cautionary labels should be placed on all chemical containers
All school division employees using hazardous substances should have access to appropriate Materials Safety Data Sheets.
Check expiration dates of chemicals
Keep only appropriate quantities of each substance on hand
Consider safer alternatives to experiments and chemicals - safer for students and for the environment
Top (http://www.saskschools.ca/curr_content/chem30_05/appendix/lab_safety.htm#Top) Basic First Aid
BleedingMinor cuts - wash the cut with soap and water and pat dry. Apply sterile bandage or dressing.
Severe - Apply pressure. Elevate. Apply dressing or bandage. Prepare to treat for shock. Seek medical assistance.
Burns, ChemicalFlood the affected area of the body with water for 20 minutes. Remove contaminated clothing. Seek medical attention.
Burns, Fire Minor burns - cool the burned skin in cool water for at least 10 min until the pain is relieved.
Severe burns - immediately start cooling the burn with cool water for at least 10 minutes. Have the victim lie down. Prepare to treat for shock. Cover the burn with clean, non-fluffy material to protect from infection; bandage loosely. Seek medical attention
Clothing on fire - STOP, DROP, and ROLL. If available wrap the victim tightly in a fire blanket or other heavy-duty fabric (wool is the best) to smother the flames. The victim should be lying down if wrapped in a blanket to avoid a "chimney effect" which would increase the severity of the fire.
Smoke and/or Fire in the Lab - Be sure to know the location of all fire exits
Minor fires - know the location of the fire extinguisher and how to use it.
Major fires - All individuals should immediately leave the laboratory. The last person leaving the lab should close the door to the laboratory. If smoke has filled the room, stay low while evacuating the room. The school fire alarm should be rung after exiting the lab.
On ALL burns DO NOT
Use lotions, ointments and creams
Use adhesive dressings
Break blisters
Eye Injuries Chemicals in the eye - Immediately flush the eye with fresh water for 15 - 30 minutes. Loosely bandage around the eyes. Seek medical attention
Foreign object in the eye - NEVER removes any object embedded in the eye! Floating objects in the eye which can be seen may be flushed from the eye with water. If flushing does not remove the object, the victim should seek medical attention.
ShockLay the casualty down, raise and support their legs. Cover with a coat or blanket to keep them warm Do not give them anything to eat or drink. Check breathing and pulse frequently. Give lots of comfort and reassurance
General Safety Guidelines
§ Be prepared for the lab before coming to class. Read over the lab before starting any experiments. Pay special attention to any safety precautions.
§ Always behave appropriately in the lab. No horseplay is allowed.
§ Report any accidents immediately to your teacher
Accidents can happen - report any problems immediately so the situation doesn't get worse
§ Clean up all spills immediately. Be sure to inform the teacher about the spill in case special methods are needed for clean up.
§ Avoid touching anything hot
§ Test any object that might be hot by placing the back of your hand about 5 cm from the object. If you feel any warmth, then the object is hot.
§ Know the location of all safety equipment in your lab as well as emergency exits. Learn how to properly use all safety equipment.
§ Avoid cutting yourself
Never use glassware that is chipped or cracked. Dispose of broken glassware in an approved container.
§ Wear sensible clothing and proper protection when heating substances.
Avoid loose clothing that may get get too close to a flame or caught in equipment. If you have long hair tie it back.
§ Always wear safety goggles when doing experiments
§ Carefully read labels on bottles
Often you will be working with chemicals that have similar names or differ only in their concentration (e.g. 0.1M HCl vs. 1.0M HCl). Always double checks to make sure you are using the correct chemical at the correct time. Never smell chemicals directly
Waft the fumes to your nose Never taste chemicals. No eating or chewing gum in the laboratory
Always clean up after yourself
Never attempt unauthorized experiments
Wash your hands with soap and water after each laboratory exercise
Learn proper handling techniques for all chemicals Acids - acids are highly corrosive, causing burns to skin and clothing.
When diluting an acid, always slowly add the acid to the water, stirring to dissipate the heat to avoid splattering. CAUTION: NEVER
pour water into a concentrated acid. Any acid spills should be dealt with promptly by neutralizing with a base. Bases - Strong bases can also cause severe burns to the skin. Bases are very dangerous if splashed into the eyes.
Mercury - mercury is highly toxic and spills are difficult to clean up. If special mercury recovery equipment is not available (sprays, wipes, etc. - available from chemistry lab suppliers) zinc dust should be used. Zinc dust reacts with mercury to form a safe mixture that is easy to handle and dispose of.
Dispose of all chemicals properly at the end of each laboratory exercise
Lab Safety Equipment
Common safety equipment in the high school lab: Fire
Extinguisher (link: Fire Safety and Fire Extinguishers (http://www.ilpi.com/safety/extinguishers.html)) Fire extinguishers are categorized by the type of fire(s) they will
extinguish; most will put out more than one type of fire. Know where your classrooms fire extinguisher is located and how to use it. Type A
Combustibles
Wood, paper, rubber, plastics
Type B
Flammable liquids
oil, grease, paint thinners
Type C
Electrical equipment
Type D
Flammable metals
Type K
Kitchen fires
Fire blanket
§ Eye wash station
First Aid kit
Safe Disposal of Chemicals
Most of the chemicals used in the standard high school chemistry lab will be nonhazardous waste and may be safely disposed of by washing down the sink with water.
Items that are safe for drain disposal include:
Organic Materials
Inorganic Materials
acetamide
§ acetic acid
acetone
ethanol
ethylene glycol
formaldehyde
methanol
propanol
Solutions of inorganic salts where both the cation and anion are listed below. Compounds containing the following that are highly acidic or basic should be neutralized first.
Some items should receive special attention; guidelines are given below for common wastes:
Acids and BasesSave these solutions in a large container and use one to neutralize the other. The neutralized solution (pH of approximately 7) may then be washed down the sink with water.
Wastes Containing Toxic Heavy Metals Copper and zinc should not be disposed of down the sink. Municipalities may have specific discharge limits for these metals.
Below is a list of chemical grades in order of purity, from highest to lowest.
ACS
Highest quality; often equals or exceeds the latest purity standards set by the American Chemical Society (ACS). This is the only universally accepted standard. Chemicals are of the highest purity attainable.
Reagent
Purity is generally equal to ACS grade. This grade is suitable for analytical work and is more than adequate for general lab use.
USP
A grade of sufficient purity to pass certain tests prescribed by the US Pharmacopoeia (USP); acceptable for drug use. USP grade may be used for most laboratory purposes.
NF
A grade of sufficient purity to meet the standards of the National Formulary (NF).
Lab
An upper-level intermediate quality. Exact impurities may not be known; however, lab grade is usually pure enough for most educational laboratories.
Pure
Purified, pure, or practical grade; a lower-level intermediate quality. Although this grade does contain impurities, it is usually pure enough for use in educational laboratories.
Technical
A good-quality grade used industrially. Use caution when substituting for reagent-grade or lab-grade chemicals.
When making a solution, one must first decide what degree of chemical purity is needed. Many types of chemicals are available in several grades of purity. Most of the chemicals listed in our catalog belong to one of the following 3 categories, in order from least pure to most pure.
Laboratory
Reagent
ACS
Choose the most appropriate grade based on need and cost. Lab-grade chemicals, because of their low cost and good chemical purity, find wide use in educational applications, such as teaching laboratories at both the secondary school and college levels. Reagent-grade chemicals are typically ACS-grade chemicals that have been repackaged and have therefore lost their ACS certification.
Carolina also offers a choice of packaging for a limited number of chemicals. Corrosive chemicals, such as concentrated acids, are normally packaged in glass bottles. For safety and convenience, our customers may order these chemicals packaged in plastic-coated safety bottles. A plastic-coated safety bottle will not shatter when dropped, which helps to contain the spill and simplify cleanup. Look at the item descriptions in the chemical section of the catalog for those chemicals available in plastic-coated safety bottles.
For safety purposes, read a chemical’s label twice before use. Read the label first when you take the chemical off the shelf and again before you remove any chemical from the bottle. When preparing solutions using concentrated chemicals, slowly add the more concentrated solution (e.g., sulfuric acid) to the less concentrated one (e.g., water). The reverse procedure can cause the solution to boil and spatter
Chemical Storage
Safety in the science classroom includes the storage of chemicals. WHMIS regulations under the Hazardous Products Act govern storage and handling practices of chemicals in school laboratories.
Key items to remember:
Chemicals should be stored in a safe location according to Chemical Class, not just alphabetically.
Appropriate cautionary labels should be placed on all chemical containers
All school division employees using hazardous substances should have access to appropriate Materials Safety Data Sheets.
Check expiration dates of chemicals
Keep only appropriate quantities of each substance on hand
Consider safer alternatives to experiments and chemicals - safer for students and for the environment
Top (http://www.saskschools.ca/curr_content/chem30_05/appendix/lab_safety.htm#Top) Basic First Aid
BleedingMinor cuts - wash the cut with soap and water and pat dry. Apply sterile bandage or dressing.
Severe - Apply pressure. Elevate. Apply dressing or bandage. Prepare to treat for shock. Seek medical assistance.
Burns, ChemicalFlood the affected area of the body with water for 20 minutes. Remove contaminated clothing. Seek medical attention.
Burns, Fire Minor burns - cool the burned skin in cool water for at least 10 min until the pain is relieved.
Severe burns - immediately start cooling the burn with cool water for at least 10 minutes. Have the victim lie down. Prepare to treat for shock. Cover the burn with clean, non-fluffy material to protect from infection; bandage loosely. Seek medical attention
Clothing on fire - STOP, DROP, and ROLL. If available wrap the victim tightly in a fire blanket or other heavy-duty fabric (wool is the best) to smother the flames. The victim should be lying down if wrapped in a blanket to avoid a "chimney effect" which would increase the severity of the fire.
Smoke and/or Fire in the Lab - Be sure to know the location of all fire exits
Minor fires - know the location of the fire extinguisher and how to use it.
Major fires - All individuals should immediately leave the laboratory. The last person leaving the lab should close the door to the laboratory. If smoke has filled the room, stay low while evacuating the room. The school fire alarm should be rung after exiting the lab.
On ALL burns DO NOT
Use lotions, ointments and creams
Use adhesive dressings
Break blisters
Eye Injuries Chemicals in the eye - Immediately flush the eye with fresh water for 15 - 30 minutes. Loosely bandage around the eyes. Seek medical attention
Foreign object in the eye - NEVER removes any object embedded in the eye! Floating objects in the eye which can be seen may be flushed from the eye with water. If flushing does not remove the object, the victim should seek medical attention.
ShockLay the casualty down, raise and support their legs. Cover with a coat or blanket to keep them warm Do not give them anything to eat or drink. Check breathing and pulse frequently. Give lots of comfort and reassurance
General Safety Guidelines
§ Be prepared for the lab before coming to class. Read over the lab before starting any experiments. Pay special attention to any safety precautions.
§ Always behave appropriately in the lab. No horseplay is allowed.
§ Report any accidents immediately to your teacher
Accidents can happen - report any problems immediately so the situation doesn't get worse
§ Clean up all spills immediately. Be sure to inform the teacher about the spill in case special methods are needed for clean up.
§ Avoid touching anything hot
§ Test any object that might be hot by placing the back of your hand about 5 cm from the object. If you feel any warmth, then the object is hot.
§ Know the location of all safety equipment in your lab as well as emergency exits. Learn how to properly use all safety equipment.
§ Avoid cutting yourself
Never use glassware that is chipped or cracked. Dispose of broken glassware in an approved container.
§ Wear sensible clothing and proper protection when heating substances.
Avoid loose clothing that may get get too close to a flame or caught in equipment. If you have long hair tie it back.
§ Always wear safety goggles when doing experiments
§ Carefully read labels on bottles
Often you will be working with chemicals that have similar names or differ only in their concentration (e.g. 0.1M HCl vs. 1.0M HCl). Always double checks to make sure you are using the correct chemical at the correct time. Never smell chemicals directly
Waft the fumes to your nose Never taste chemicals. No eating or chewing gum in the laboratory
Always clean up after yourself
Never attempt unauthorized experiments
Wash your hands with soap and water after each laboratory exercise
Learn proper handling techniques for all chemicals Acids - acids are highly corrosive, causing burns to skin and clothing.
When diluting an acid, always slowly add the acid to the water, stirring to dissipate the heat to avoid splattering. CAUTION: NEVER
pour water into a concentrated acid. Any acid spills should be dealt with promptly by neutralizing with a base. Bases - Strong bases can also cause severe burns to the skin. Bases are very dangerous if splashed into the eyes.
Mercury - mercury is highly toxic and spills are difficult to clean up. If special mercury recovery equipment is not available (sprays, wipes, etc. - available from chemistry lab suppliers) zinc dust should be used. Zinc dust reacts with mercury to form a safe mixture that is easy to handle and dispose of.
Dispose of all chemicals properly at the end of each laboratory exercise
Lab Safety Equipment
Common safety equipment in the high school lab: Fire
Extinguisher (link: Fire Safety and Fire Extinguishers (http://www.ilpi.com/safety/extinguishers.html)) Fire extinguishers are categorized by the type of fire(s) they will
extinguish; most will put out more than one type of fire. Know where your classrooms fire extinguisher is located and how to use it. Type A
Combustibles
Wood, paper, rubber, plastics
Type B
Flammable liquids
oil, grease, paint thinners
Type C
Electrical equipment
Type D
Flammable metals
Type K
Kitchen fires
Fire blanket
§ Eye wash station
First Aid kit
Safe Disposal of Chemicals
Most of the chemicals used in the standard high school chemistry lab will be nonhazardous waste and may be safely disposed of by washing down the sink with water.
Items that are safe for drain disposal include:
Organic Materials
Inorganic Materials
acetamide
§ acetic acid
acetone
ethanol
ethylene glycol
formaldehyde
methanol
propanol
Solutions of inorganic salts where both the cation and anion are listed below. Compounds containing the following that are highly acidic or basic should be neutralized first.
Some items should receive special attention; guidelines are given below for common wastes:
Acids and BasesSave these solutions in a large container and use one to neutralize the other. The neutralized solution (pH of approximately 7) may then be washed down the sink with water.
Wastes Containing Toxic Heavy Metals Copper and zinc should not be disposed of down the sink. Municipalities may have specific discharge limits for these metals.