Laboratory chemicals can become dangerous over time in different ways. The danger can be due to chemical degradation, contamination, or reaction with air in the container headspace. These processes can result in over-pressurization of containers or production of new compounds with increased toxicity or other hazardous properties. Time-sensitive chemicals must be properly handled and stored to minimize these additional hazards.
Review the table below for recommended Maximum Storage Times and management practices for these chemicals:
| MATERIAL | ADDITIONAL HAZARD | MAXIMUM STORAGE TIME | TESTING/STORAGE REQUIRMENTS |
|---|---|---|---|
| Picric Acid | Highly Explosive when Dry | 2 Years | Must be kept wet. Inspect regularly and add liquid. |
| Anhydrous Hydrogen Halide Gas Cylinders (HBr, HF, HCl, etc) | Moisture infiltration causes corrosion of the metal cylinder and generates Hydrogen gas. Pressure rises and cylinder weakens until it explodes, releasing toxic/corrosive gas. | By expiration date or 2 years after purchase, whichever is shorter. | Hazard is not visible. Check if cylinder pressure is rising. This indicates Hydrogen formation. |
| Alkali-Metal Amides (Potassium Amide, Sodium Amide) | React with oxygen to form nitrite and trace amounts of hyponitrite. Exposure to any oxygen can eventually result in spontaneous explosion. | One year after opening or two years after purchase, whichever is shorter. | Store in a glove box immediately and ensure no contact with oxygen. |
| Alkali Metals (Sodium, Potassium, etc) | React with oxygen and water during storage, even under oil, causing a crust to grow which may explode on disturbance, such as cutting. | Dispose when expired, if discolored (white, yellow, pale grey), or if thick furry crust is visible. | Inspect at least annually. |
| Chloroform | Decomposes over time to form Phosgene gas, which is much more toxic than Chloroform. | Dispose 12 months after opening or after 3 years if unopened. Unstabilized: Dispose after 12 months. | Purchase with Ethanol stabilizer. Store in the dark and avoid exposure to oxygen. Always use in a Chemical Fume Hood. |
| Nitric Acid (>50% stored in High-Density Polyethylene bottles) | Degrades the plastic container. When container fails, releasing corrosive liquid and toxic fumes. | Dispose after 2 years. | Store in glass bottles. |
| Formic Acid (>90% stored in unvented glass containers) | Decomposes to form Carbon Monoxide gas and water. In a sealed glass container, builds up pressure and can explode. | Vent every 12 months. Dispose after expiration. | Store in vented containers or vent regularly. |
| Hydrogen Peroxide (>30% in unvented containers) | Decomposes over time, forming oxygen gas and pressurizing the container. | Vent regularly. Dispose after expiration or 12 months. | Store in vented containers. Refrigerate to increase shelf life. |
Picric Acid
Picric Acid is a pale yellow chemical usually stored moistened with water or in a solution with water or ethanol. When dried, it is a powerful explosive. Dispose 2 years after purchase. Bouin's Solution contains Picric Acid and must be managed in the same way as Picric Acid solutions.
Inspect regularly (at least quarterly) for drying and add water as needed to maintain a visible layer of liquid in the container:
- Check for crust or crystal formation around the lid, on the container, and/or inside the container. If present, restrict access to the container and contact OEHS@tulane.edu.
- For moistened/saturated picric acid, ensure the container has between 30-40% volume of water above the solid to maintain safe saturation.
Alkali-Metal Amides
This category includes Potassium Amide and Sodium Amide. They are sometimes listed as Peroxide Formers but do not generate organic peroxides. They are highly reactive, combustible solids that form explosive nitrite and hyponitrite in the presence of oxygen. Testing or inspecting these materials is not practical. Dispose 1 year after opening or 2 years after purchase, whichever comes first. Always store in a glove box under an inert atmosphere.
Alkali Metals
Alkali Metals such as Sodium or Potassium react with oxygen and water during storage (even under oil), to form oxides and superoxides that can catch fire or explode upon disturbance. The oxidation forms a yellow or orange crust or coating. Alkali metals should be checked annually for signs of oxidation. Dispose if they exhibit signs of oxidation.
Hydrogen Halide Compressed Gas Cylinders
Anhydrous Hydrogen Fluoride Cylinder Failure
| Hydrogen Fluoride | Hydrogen Sulfide | Hydrogen Chloride |
| Hydrogen Bromide | Hydrogen Cyanide |
|
The compressed gases listed above have a shelf-life provided by the manufacturer that must be strictly followed. In the absence of an expiration date, dispose 2 years after purchase. There have been numerous incidents involving these compounds related to storage past the expiration date. Over time, moisture can slowly enter the cylinder, which initiates corrosion. As the corrosion continues, the gas slowly reacts with the internal metal walls of the cylinder to produce Hydrogen. The walls of the cylinder weaken due to corrosion, while at the same time the internal pressure increases due to the Hydrogen generated. Ultimately, these cylinders fail and create dangerous projectiles and toxic gas releases. If cylinder pressure begins rising, return to manufacturer.
Chloroform
Chloroform, when exposed to air and light, can degrade to form phosgene—a highly toxic gas. This reaction is catalyzed by oxygen and UV light. Store in the dark and always purchase Chloroform stabilized with Ethanol. Dispose 12 months after opening or after 3 years if unopened. Other stabilizers than ethanol are not as effective in preventing degradation. If the Chloroform is not stabilized with ethanol, dispose after 12 months even if unopened.
Nitric Acid in HDPE
Nitric acid is a strong oxidizer that degrades High Density Polyethylene containers over time, especially at concentrations above 50%. This leads to embrittlement and eventual failure of the container, resulting in leaks of corrosive liquid and toxic fumes. Dispose of HDPE containers of Nitric Acid after 2 years. Purchase Nitric Acid in glass bottles.
Formic Acid
Concentrated formic acid slowly decomposes into carbon monoxide and water, especially when exposed to heat or light. In sealed containers, this gas buildup can lead to overpressurization and potential explosion. Vent containers every 12 months or store in containers with vented caps. Dispose of container on expiration.
Hydrogen Peroxide
Concentrated (>30%) Hydrogen Peroxide decomposes over time into oxygen and water, especially when exposed to heat or light. In sealed glass containers, this gas buildup can lead to overpressurization and potential explosion. Store in a vented container or vent container regularly. Dispose after 1 year.
