Difference between revisions of "Safe handling and storage of chemicals"

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Storage of many chemicals require additional or special requirements, to avoid hazards as well as contamination.

Storage area guidelines

Storage cabinets and shelves

• Oxidizing acids and flammable solvents must be stored in separate locations.
• Solvents in general must be stored away from any source of heat and light.
• Hazardous materials, especially those that are water sensitive, should not be stored under sinks (except cleaners).^[1]

Corrosive chemicals cabinet

Strong acids are usually stored here

• Such cabinets should either be made from chemical resistant materials or lined with such.
• A double door is recommended.
• Scrubbers are optional, but recommended. A open container of baking soda should take care of acidic vapors.
• Do not store metals or other reducing chemicals in the same cabinet.
• Do not store nitrates and oxochlorine anions in the acids cabinet.
• Amines should also not be stored in the same cabinet as acids, as their fumes will react to form a very fine dust.

Refrigerators

Refrigerators can be used to store volatile substances and to cool exothermic reactions. Although domestic refrigerators can be used to store many chemicals, they are unsuitable for storing corrosive chemicals, such as acids. Several important guidelines:

• Avoid storing acids, as the escaping vapors will corrode the refrigerator.
• Do not store food in the same refrigerator. Do not reuse a chemical refrigerator for food.

Cryonics

• Avoid storing the cryogenic container in light or near a heat source.
• Periodically check the valves.
• Always ensure that cryogenic container has a pressure release valve

Distillation

• Always turn on the cooling first before performing any other operation.
• Ethers must never be distilled to dryness, as they tend form explosive peroxides during storage that can explode when dry.

Containers

• Never store solvents in plastic containers, even those which are supposed to be insoluble in the solvent.
• Periodically open the lids of chemicals which decompose, to allow pressure buildup to release itself. ALWAYS do this when you move a solvent bottle from a cold place to a warm one (some solvents have a very high vapor pressure and can burst if too much pressure builds up inside the reagent bottle).
• Although it is usually not a safety hazard, make sure to store dehydrated chemicals in completely sealed,(usually) glass, containers.

Storage of specific materials

Alkali metals

Lithium

Lithium poses an unusual problem in that it is lighter than almost every single nonpolar organic solvent. The only ones in which it sinks are liquid ethane and methane. Weighting pieces of lithium down with a heavier metal, such as copper or lead, is common practice.

Sodium

Sodium is more reactive than lithium, but it's denser than mineral oil and most organic solvents and can be easily stored for months.

Potassium

Potassium is more reactive than the first two and while it can be stored under mineral oil, it will corrode much faster. Sealing the bottle is recommended. Ampouling is sometimes used.

Rubidium and Cesium

Both Rubidium and Cesium are extremely reactive and even pyrophoric. They can only be stored under mineral oil for short periods, ampouling is used instead.

NaK

Unlike the pure alkali metals, the sodium-potassium mixture, in a 77:23 K-Na ratio, is liquid at standard conditions. It is pyrophoric and less dense than water. It is usually stored under hexane or ampouled, since it's lighter than most organic solvents used to store alkali metals. It will also corrode PTFE.

White phosphorus

White phosphorus should be tightly sealed in an extremely durable container, away from light to prevent degradation. WP can be safely stored underwater.

Handling

Acids

Hydrofluoric acid

Hydrofluoric acid should never be kept or handled in glass containers (e.g. beakers), because of its ability to dissolve (most) oxides and silicates. It should be handled in thick plastic containers.

Perchloric acid

The maximum concentration at which perchloric acid can be safely stored is 70%. As it is a very powerful oxidizer, all the glassware where is about to be poured in should be inspected for any organic traces.

Incompatible chemicals

References

1. ↑ http://www2.lbl.gov/ehs/chsp/html/storage.shtml
2. ↑ http://ccc.chem.pitt.edu/wipf/Web/Chemical_Incompatibilities.pdf