Reagent preservation

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
Citric acid	Anti-fungal agents	Aqueous solutions and wet citric acid are prone to mold, much less so while dry
Dichloromethane	Ethanol
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
Potassium ferrate	Potassium hydroxide
Schweizer's reagent	Excess ammonia
Sodium ferrate	Sodium hydroxide
Tetraamine copper(II) complex	Excess ammonia
Tetraaminecopper(II) persulphate	Excess ammonia
Tetrahydrofuran	Butylated hydroxytoluene (BHT), Butylated hydroxyanisole (BHA), fresh copper