preface to fifteenth edition

11.2 DRYING AND HUMIDIFICATION
TABLE 11.3
Drying Agents
Drying agent
Most useful for
Residual water,
mg H 2 O per liter
of dry air (25C)
Grams water
removed per gram
of desiccant
Regeneration,
C
Al 2 O 3 Hydrocarbons 0.002–0.005 0.2 175 (24 h)
a
Ba(ClO 4 ) 2 Inert gas streams 0.6–0.8 0.17 140
BaO Basic gases: hydrocarbons, aldehydes, alcohols 0.0007–0.003 0.12 1000
b
CaC 2 Ethers 0.56 Impossible
c
CaCl 2 Inert organics 0.1–0.2 0.15 (1 H 2 O)
250
0.30 (2 H 2 O)
d
CaH 2 Hydrocarbons, ethers, amines, esters, higher alcohols 1 10 5 0.85 Impossible
CaO Ethers, esters, alcohols, amines 0.01–0.003 0.31 Difficult, 1000
CaSO 4 Most organic substances 0.005–0.07 0.07 225
Dow Desiccant 812 e Most materials (5–200 ppm) No
K 2 CO 3 Most materials except acids and phenols 0.16 158
KOH Amines 0.01–0.9 Impossible
LiAlH4 f
Hydrocarbons 1.9 Impossible
a
Mg(ClO 4 ) 2 Gas streams 0.0005–0.002 0.24 250 (high vacuum)
MgO All but acidic compounds 0.008 0.45 800
MgSO 4 Most organic compounds 1–12 0.15–0.75 Not feasible
Molecular sieves: 4X Molecules with effective diameter 4Å 0.001 0.18 250
5X Molecules with effective diameter 5Å 0.001 0.18 250
9.5% Na-Pb alloy d Hydrocarbons, ethers (For solvents only) 0.08 Impossible
Na 2 SO 4 Ketones, acids, alkyl and aryl halides 12 1.25 150
P 2 O 5
Gas streams; not suitable for alcohols, amines, ketones,
2 10 5 0.5 Not feasible
or amines
Silica gel Most organic amines 0.002–0.07 0.2 200–350
Sulfuric acid Air and inert gas streams 0.003–0.008 Indefinite Not feasible
a
May form explosive mixtures when contacting organic material. b
Explosive C 2 H 2 formed. c
Slow in drying action.
d
H 2 formed. e
Used as column drying of organic liquids. f
Strong reductant.
11.5