Chemical Hygiene Plan - Queensborough Community College ...
Chemical Hygiene Plan - Queensborough Community College ... Chemical Hygiene Plan - Queensborough Community College ...
liquid hydrogen service must be purged with helium or gaseous hydrogen, with proper precautions, before using. • The safety philosophy in the use of liquid hydrogen can be summarized as the following: o Isolation of the experiment. o Provision of adequate ventilation. o Exclusion of ignition sources plus system grounding/bonding to prevent static charge build-up. o Containment in helium purged vessels. o Efficient monitoring for hydrogen leakage. o Limiting the amount of hydrogen cryopumped in the vacuum system. 22.11 Extractions and Distillations Extractions • Do not attempt to extract a solution until it is cooler than the boiling point of the extractant due to the risk of overpressurization, which could cause the vessel to burst. • When a volatile solvent is used, the solution should be swirled and vented repeatedly to reduce pressure before separation. • When opening the stopcock, your hand should keep the plug firmly in place. • The stopcock should be lubricated. • Vent funnels away from ignition sources and people, preferably into a hood. • Keep volumes small to reduce the risk of overpressure and if large volumes are needed, break them up into smaller batches. Distillations • Avoid bumping (sudden boiling) since the force can break apart the apparatus and result in splashes. Bumping can be avoided by even heating, such as using a heat mantle. Also, stirring can prevent bumping. Boiling stones can be used only if the process is at atmospheric pressure. • Do not add solid items such as boiling stones to liquid that is near boiling since it may result in the liquid boiling over spontaneously. • Organic compounds should never be allowed to boil to dryness unless they are known to be free of peroxides, which can result in an explosion hazard. Reduced pressure distillation • Do not overheat the liquid. Superheating can result in decomposition and uncontrolled reactions. • Superheating and bumping often occur at reduced pressures so it is especially important to abide by the previous point on bumping and to ensure even, controlled heating. Inserting a nitrogen bleed tube may help alleviate this issue. • Evacuate the assembly gradually to minimize bumping. 139
• Allow the system to cool and then slowly bleed in air. Air can cause an explosion in a hot system (pure nitrogen is preferable to air for cooling). • See “reduced pressure” for vacuum conditions. 22.12 Glass Under Vacuum Reduced pressure Some general guidelines for glass under vacuum include: • Inspect glassware that will be used for reduced pressure to make sure there are no defects such as chips or cracks that may compromise its integrity. • Only glassware that is approved for low pressure should be used. Never use a flat bottom flask (unless it is a heavy walled filter flask) or other thin walled flask that are not appropriate to handle low pressure. • Use a shield between the user and any glass under vacuum or wrap the glass with tape to contain any glass in the event of an implosion. Vacuum pumps • Cold traps should be used to prevent pump oil from being contaminated which can create a hazardous waste. • Pump exhaust should be vented into a hood when possible. • Ensure that all belts and other moving parts are properly guarded. • Whenever working on or servicing vacuum pumps, be sure to follow appropriate lock-out procedures. 22.13 Glassware Washing In most cases laboratory glassware can be cleaned effectively by using detergents and water. In some cases it may be necessary to use strong chemicals for cleaning glassware. Strong acids should be avoided unless necessary. In particular, Chromic acid should not be used due to its toxicity and disposal concerns. One product that may be substituted for Chromic acid is “Nochromix Reagent”. The Fisher catalog describes this material as: “Nochromix Reagent. Inorganic oxidizer chemically cleans glassware. Contains no metal ions. Rinses freely—leaving no metal residue, making this product valuable for trace analysis, enzymology, and tissue culture work. (Mix with sulfuric acid).” Unused Nochromix Reagent can be neutralized to a pH between 5.5 and 9.5 and drain disposed. Acid/base baths should have appropriate labeling and secondary containment. Additionally a Standard Operating Procedure (SOP), proper personal protective equipment (PPE), and spill materials should be available. Proper disposal for spent acid/base bath contents is neutralization and drain disposal. 140
- Page 89 and 90: your College’s Emergency Procedur
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- Page 115 and 116: the same regulations and laws; and
- Page 117 and 118: problems and compliance issues, and
- Page 119 and 120: from any given amperage, the table
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- Page 123 and 124: "reset" buttons. They are found on
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- Page 139: frozen to the underlying skin, cold
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- Page 161 and 162: • Where airborne exposure monitor
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- Page 165 and 166: APPENDIX B: SITE MAP 164
- Page 167 and 168: APPENDIX D: OSHA TOXIC SUBSTANCES L
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- Page 173 and 174: peroxide, Nitric acid, Sodium perox
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- Page 185 and 186: APPENDIX L: HOW TO UNDERSTAND MATER
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liquid hydrogen service must be purged with helium or gaseous hydrogen, with proper<br />
precautions, before using.<br />
• The safety philosophy in the use of liquid hydrogen can be summarized as the following:<br />
o Isolation of the experiment.<br />
o Provision of adequate ventilation.<br />
o Exclusion of ignition sources plus system grounding/bonding to prevent static<br />
charge build-up.<br />
o Containment in helium purged vessels.<br />
o Efficient monitoring for hydrogen leakage.<br />
o Limiting the amount of hydrogen cryopumped in the vacuum system.<br />
22.11 Extractions and Distillations<br />
Extractions<br />
• Do not attempt to extract a solution until it is cooler than the boiling point of the<br />
extractant due to the risk of overpressurization, which could cause the vessel to burst.<br />
• When a volatile solvent is used, the solution should be swirled and vented repeatedly to<br />
reduce pressure before separation.<br />
• When opening the stopcock, your hand should keep the plug firmly in place.<br />
• The stopcock should be lubricated.<br />
• Vent funnels away from ignition sources and people, preferably into a hood.<br />
• Keep volumes small to reduce the risk of overpressure and if large volumes are needed,<br />
break them up into smaller batches.<br />
Distillations<br />
• Avoid bumping (sudden boiling) since the force can break apart the apparatus and result<br />
in splashes. Bumping can be avoided by even heating, such as using a heat mantle. Also,<br />
stirring can prevent bumping. Boiling stones can be used only if the process is at<br />
atmospheric pressure.<br />
• Do not add solid items such as boiling stones to liquid that is near boiling since it may<br />
result in the liquid boiling over spontaneously.<br />
• Organic compounds should never be allowed to boil to dryness unless they are known to<br />
be free of peroxides, which can result in an explosion hazard.<br />
Reduced pressure distillation<br />
• Do not overheat the liquid. Superheating can result in decomposition and uncontrolled<br />
reactions.<br />
• Superheating and bumping often occur at reduced pressures so it is especially important<br />
to abide by the previous point on bumping and to ensure even, controlled heating.<br />
Inserting a nitrogen bleed tube may help alleviate this issue.<br />
• Evacuate the assembly gradually to minimize bumping.<br />
139
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