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.

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

  1. https://www.youtube.com/watch?v=7oAcT4Duun4
  2. http://www.sigmaaldrich.com/chemistry/solvents/learning-center/stabilizer-systems.html
  3. http://www.sigmaaldrich.com/chemistry/solvents/learning-center/stabilizer-systems.html
  4. http://www.sigmaaldrich.com/chemistry/solvents/learning-center/stabilizer-systems.html
  5. https://www.google.com/patents/US2511072
  6. http://www.sigmaaldrich.com/chemistry/solvents/learning-center/stabilizer-systems.html

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