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, 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 added must be greater compared to other ethers
Hydrogen peroxide	Phosphoric acid
Lead(II) azide	Dextrin	Generally used in Pb(N3)2 aqueous solutions and during production
Lead(IV) acetate	Anhydrous acetic acid
Methyl iodide	Copper or silver wire/powder
Pentaerythritol tetranitrate	Urea
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