Drying Agent Selection Guide


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Drying Agent

Suitable for Drying

NOT Suitable for Drying

Residual Water mg H2O/L Dried Air

g H2O/g Desiccant

Regeneration

Reaction Mechanism

Aluminum Oxide

Hydrocarbons, air, ammonia, argon, helium, nitrogen, oxygen, Freon, H2O, CO2, SO2

 

0.003

0.2

175C

Chemisorption Adsorption

ANHYDRONE® (Magnesium Perchlorate anhydrous)

Inert gas, air

Most Organics (May form explosive compound when exposed to organic vapors.)

0.001

0.2

250C with Vacuum

Hydration

Barium Oxide

Organic bases, alcohols, aldehydes, amines

Acidic Compounds, CO2

0.00065

0.1

Not Recommended

Absorption and Adsorption

Boric Anhydride

Formic Acid

   

0.8

450C

 

Calcium Chloride (<20 Mesh)

Alkyl and Aryl Halides, most esters, saturated and aromatic hydrocarbons, ethers

Alcohols, amines, phenols, aldehydes, amides, amino acids, some esters, ketones

0.14-0.25

0.2 (1H2O)
0.3 (2H2O)

250C

Hydration

Calcium Oxide

Alcohols, amines and ammonia gas

Acidic compounds, esters

0.007

0.3

1000C

Chemisorption

Calcium Sulfate

Most organic compounds

 

0.005

0.066

235C

Absorption

Cupric Sulfate

Esters, alcohols (excellent for benzene and toluene)

 

1.4

0.6

200C

 

Lithium Aluminum Hydride

Aldehydes, ketones, esters, carboxylic acids, peroxides, acid anhydrides, acid chlorides, ethers

Acid and its derivatives, aromatic nitro compounds

       

Magnesium Oxide

Hydrocarbons, aldehydes, alcohols, basic gases, amines

Acidic compounds

0.008

0.5

800C

Hydration

Magnesium Sulfate

Most compounds, incl. Acids, ketones, aldehydes, esters, nitriles

Acid sensitive compounds

1.0

0.2 ­ 0.8

200C and red heat

Hydration

Molecular Sieve Activated Type 3A

Molecules of diameter >3 angstroms

Molecules of diameter <3 angstroms

 

0.18

117-260C

Adsorption

Molecular Sieve Activated Type 4A

Molecules of diameter >4 angstroms

Molecules of diameter <4 angstroms, Ethanol, H2S, CO2, SO2, C2H4, C3H4, and strong acids

0.001

0.18

250C

Adsorption

Molecular Sieve Activated Type 5A

Molecules of diameter > 5 angstroms, e.g., branched chain compounds and those having 4 carbon or larger rings

Molecules of diameter <5 angstroms, e.g., butanol, n-C4H10 to n-C22H46

0.003

0.18

250C

Adsorption

Phosphoric Acid

   

0.003

 

Not recommended

Absorption and Solution

Phosphorous Pentoxide

Saturated hydrocarbons, aromatic hydrocarbons, ethers, alkyl halides, aryl halides, nitriles, anhydrides, nitrites, esters

Alcohols, acids, amines, ketones, HF and HCl vapors

3x10-5

0.5

No

Chemisorption leading to H3PO4

Potassium Carbonate

Alcohols, nitriles, ketones, esters, amines

Acids, phenols

 

0.2

300 C

Hydrate Formation

Potassium Hydroxide

Amines, organic bases

Acids, phenols, esters, amides, acidic gases, aldehydes

0.3

Indeterminate

No

Hydration and Solution Formation

Silica Gel 6-16 Mesh

Most organics

HF vapors

0.03

0.2

200-350C

Adsorption

Sodium

Saturated and aromatic hydrocarbons, ethers

Acids, alcohols, aldehydes, ketones, amines, esters, organic halides, and any substance with high water content

   

Not Recommended

Leads to

NaOH + H2

Sodium Hydroxide Pellets

Amines

Acids, phenols, esters, amides

0.16

Indefinite

Not Recommended

Absorption and Solution Formation

Sodium Sulfate Anhydrous

Alkyl halides, aryl halides, aldehydes, ketones, acids

 

12

1.2

150C

Hydration

Sulfuric Acid

Inert gases, HCl, Cl2, CO, SO2, air used in desiccators

Too reactive to actually contact organic materials

0.003

Indefinite

No

Hydration

Zinc Chloride

Hydrocarbons

Ammonia, amines, alcohol

0.9

0.2

110C

Hydration