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 ether 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
Barium ferrate Potassium hydroxide, sodium hydroxide
Chloroform Ethanol, methanol
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
Diethyl ether Butylated hydroxytoluene (BHT), Butylated hydroxyanisole (BHA), fresh copper
Diisopropyl ether Butylated hydroxytoluene (BHT), Butylated hydroxyanisole (BHA), fresh copper The amount of preservative must be much higher that in the case of other ethers
Diethyl ether Butylated hydroxytoluene (BHT), Butylated hydroxyanisole (BHA), fresh copper
Hydrogen peroxide Phosphoric acid
Lead(II) azide Dextrin Generally used in Pb(N3)2 aqueous solutions and during production
Potassium ferrate Potassium hydroxide
Schweizer's reagent Excess ammonia
Smokeless powder Diphenylamine
Sodium ferrate Sodium hydroxide
Tetraamine copper(II) complex Excess ammonia
Tetraaminecopper(II) persulphate Excess ammonia
Tetrahydrofuran Butylated hydroxytoluene (BHT), Butylated hydroxyanisole (BHA), fresh copper

References

Relevant Sciencemadness threads