From the safety exercises associated with the Year 1 & 2 Level 5 Pre-labs you should have, and be continuing to be, gaining familiarity with the terminology associated with the safe use of chemicals and will also have built up a degree of knowledge of the hazards associated with certain chemicals.
However these activities are a passive learning exercise, in that they give you a grounding of safety knowledge but do not require you to apply that knowledge in assessing risk for yourself, i.e. you simply needed to be aware of the chemical hazards and to follow the issued safety instructions.
The Year 2 Level 4 Lab Blackboard
quizzes are in part designed to address this, in requiring you to take your knowledge and use it to assess hazards/risks for a particular chemical/practical. (Note: You may in Year 3 or Year 4 need to go even further and perform a complete risk assessment from start to finish.)
IDENTIFYING HAZARDS
Before performing any experimental work you must always be aware of the hazards of the chemicals you are handling. This also includes the waste and disposal procedures for each chemical used. For most of your Year 2 practicals, part of your pre-lab requirement will be to answer a Blackboard quiz on this - in effect completing the blanked out entries on the "Understanding Hazard, Minimising Risk" table in the laboratory script for the practical.
To do this it is recommended that you first find the appropriate chemical Material Safety Data Sheet (MSDS) for the relevant chemicals. A good source for MSDS is Sigma-Aldrich.
In addition to the MSDS, you should also use as a source the completed entries on the "Understanding Hazard, Minimising Risk" table in the laboratory script for the practical, since it may provide safety information for chemicals similar to the one you are safety assessing. For example if you are assessing the hazards associated with a compressed nitrogen cylinder and safety information is supplied in the script for a compressed hydrogen cylinder, then some of these hazards will apply equally to both (- although you will need to use your judgement to decide which).
ASSESSING HAZARDS
The safety information you have obtained will need to be applied to the experiment at hand, i.e. you will need to consider how the amount, concentration, phase and use of the chemical will influence its hazards.
Example: If the MSDS stated to avoid inhaling dust but the chemical is supplied for the practical as a dilute solution, then this would be redundant as a hazard.
You may also need to compare hazards, i.e. which of the hazards for this reagent is the most significant (in the context of its usage)? In this case you will need to consider the inherent level of each hazard as well as the amount, phase, concentration and use of the reagent.
Example: Ethanol is hazardous if inhaled and also as a fire risk. You might consider that the most significant of these is the fire risk. However, if you are using a small quantity of warmed ethanol in an enclosed space with no obvious ignition sources, the most significant likely issue would be the inhalation effects.
A further consideration (which will not be covered by any single MSDS) is the proper disposal of mixtures, In this case the initial treament will need to be decided based on which is the most hazardous or significant component.
Example:: For a solution containing iodine and potassium iodide in sulphuric acid, you would first need to neutralize the iodine (to a safe product) in the solution, before considering disposing of the solution as sulphuric acid waste.
ADDITIONAL NOTE ON HAZARD PHRASES
It is worth noting that the hazard phrases/numbers used represent bands of hazard, i.e. not all reagents with the same hazard identification will have exactly the same level of hazard.
Example: Consider molydenum hexacarbonyl and sodium cyanide, both of which are listed as "fatal if inhaled" (H330). However if we take the IDLH (i.e. the airborne amount which would be Immediately Dangerous to Life or Health) value as a measure of their toxicity, then sodium cyanide would be considered 200 times more dangerous than molybdenum hexacarbonyl (i.e. molydenum hexacarbonyl IDLH = 5000 mgm-3; sodium cyanide IDLH = 25 mgm-3.
ADDITIONAL NOTES ON YEAR 2 PRE-LAB QUIZZES & SAFETY
- For some quiz questions you may decide that more than one of listed answers is applicable (i.e. correct). In this case you will need to use your judgement to decide which of the answers is most appropriate (or significant).
- For some quizzes you will note that some questions are repeated. If you are paying attention you will realise that although the questions may be the same, the list of possible answers will have been varied (although some of the previously listed answers may still appear). Again, for each of these questions you need to identify the most appropriate (or significant) answer from the list supplied for that question.
- If, as part of the automated feedback you receive after taking the quiz, you are instructed to investigate more thoroughly the hazards associated with a particular reagent - You should ensure you do this prior to attending the lab.
- If, having attempted the quiz and performed any recommended additional research, you are unsure if you fully appreciate/understand the hazards associated with a particular reagent (or procedure) - Please raise this with a demonstrator in the lab.