Difference between revisions of "Reagent preservation"
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Although most chemical compounds can be stored indefinitely (ex: sodium chloride, barium sulfate, etc.) in most if not all storage conditions, there are quite a lot of reagents that tend to undergo chemical changes, regardless of the storage. Even in the best storage conditions, they will degrade over long periods of time. To maintain the long shelf life of them, preservatives as well as other additives are added.
Contents
General
Many chemicals, such as ethers, tend to undergo autoxidation when in contact with air. Halogenated carbons will too suffer similar effects.
Other compounds, such as sugar or citric acid will serve as nourishment for mold or other biological organisms.
Note that preservatives have poor efficiency if you do not store your reagents properly.
Reagents and preservatives used
| Compound | Preservative | Notes |
|---|---|---|
| 1,4-Dioxane | Butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), fresh copper, diphenylamine, hydroquinone | |
| Acrolein | Hydroquinone | Does not always work, possibly due to impurities[1] |
| Barium ferrate | Potassium hydroxide, sodium hydroxide | |
| Chloroform | Ethanol, methanol, pentene (amylene) | Accepted values of 1% for ethanol; 100 ppm for amylene[2] |
| Citric acid | Anti-fungal agents | Aqueous solutions and wet citric acid are prone to mold; solid or anhydrous citric acid less so |
| Dichloromethane | Ethanol, methanol, cyclohexane, cyclohexene, amylene | Accepted values of 100 ppm for amylene, cyclohexane, cyclohexene[3] |
| Diethyl ether | Butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), fresh copper, diphenylamine, ethanol, hydroquinone | Accepted values 1-2% for ethanol[4] |
| Diisopropyl ether | Butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), fresh copper, diphenylamine, hydroquinone | The amount of preservative added must be greater compared to other ethers |
| Formaldehyde | Methanol | For aqueous formaldehyde (Formalin) the concentration is 10-20%; Inhibts oxidation and polymerization |
| Hydrogen peroxide | Phosphoric acid, EDTA | |
| Isopropanol | Butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), fresh copper, diphenylamine, hydroquinone | Only required if kept for more than 1-2 years in contact with air |
| Lead(II) azide | Dextrin | Generally used in Pb(N3)2 aqueous solutions and during production to inhibit the growth of large crystals |
| Lead(IV) acetate | Anhydrous (glacial) acetic acid | |
| Methyl iodide | Copper or silver wire/powder | |
| Pentaerythritol tetranitrate | Urea | |
| Potassium ferrate | Potassium hydroxide | |
| Schweizer's reagent | Excess ammonia | |
| sec-Butanol | Butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), fresh copper, diphenylamine, hydroquinone | Only required if kept for more than 1-2 years in contact with air |
| Smokeless powder | Diphenylamine | |
| Sodium ferrate | Sodium hydroxide | |
| Sulfur trioxide | Antimony pentafluoride, Antimony pentachloride | Concentration 0.5-1%; antimony pentafluoride gives a better performance than the pentachloride[5] |
| Tetraamine copper(II) complex | Excess ammonia | |
| Tetraaminecopper(II) persulphate | Excess ammonia | |
| Tetrahydrofuran | Butylated hydroxytoluene (BHT), Butylated hydroxyanisole (BHA), fresh copper, diphenylamine, hydroquinone | Accepted values of 100-300 ppm for BHT[6] |
References
- ↑ https://www.youtube.com/watch?v=7oAcT4Duun4
- ↑ http://www.sigmaaldrich.com/chemistry/solvents/learning-center/stabilizer-systems.html
- ↑ http://www.sigmaaldrich.com/chemistry/solvents/learning-center/stabilizer-systems.html
- ↑ http://www.sigmaaldrich.com/chemistry/solvents/learning-center/stabilizer-systems.html
- ↑ https://www.google.com/patents/US2511072
- ↑ http://www.sigmaaldrich.com/chemistry/solvents/learning-center/stabilizer-systems.html
