PURIFICATION OF LABORATORY CHEMICALS pot

PURIFICATION OFLABORATORY CHEMICALS Wilfred L.. COMMON PHYSICAL TECHNIQUES USED IN PURIFICATION 1Sily lation of glassware and plasticware .4 SAFETY PRECAUTIONS ASSOCIATED WITH THE PURIFI

PURIFICATION OF

LABORATORY CHEMICALS

Wilfred L F.Armarego Christina U Un Chai

COMMON PHYSICAL TECHNIQUES USED IN PURIFICATION 1

Sily lation of glassware and plasticware 4 SAFETY PRECAUTIONS ASSOCIATED WITH THE PURIFICATION

SOME HAZARDS OF CHEMICAL MANIPULATION IN PURIFICATION AND

Salts and organic esters of some inorganic acids 6

METHODS OF PURIFICATION OF REAGENTS AND SOLVENTS 7

Isopiestic or isothermal distillation 14

Vapour phase chromatography (GC or gas-liquid chromatography) 18

Preparation and standardisation of alumina 20

Pr e paration of oth e r adsorb e nts 21

Flash Chromatography (FC and HPFC) 22

Ion-exchang e ce llulos e s and sephade x 24

Sephad ex 24

Cr ys tallin e h y dro xy lapatit e 25

High performance liquid chromatography (HPLC) 25 Other types of liquid chromatography 26 Automated column chromatography 27

Removal of solvents 27 Removal of water 27 Intensity and capacity of common desiccants 28 Suitability of individual desiccants 2

Molecular sieves 3

MISCELLANEOUS TECHNIQUES 3

Freeze-pump-thaw and purging 3

Va uum lines, Schlenk and glovebox techniques 3

PROPERTIES USEFUL IN PURIFICATION 32

Ionisation constants - pK 3

pK and temperature 3

pK and solvent 33 Sol ubilities of gases in liquids 33 CHEMICAL AND BIOCHEMICAL SOURCES 34

TABLE 1

FIGURE 1

TABLE 2A

TABLE 2B

TABLE 3

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TABLE 5

TABLE 6

TABLE 7

TABLE 8

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TABLE 10

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TABLE 12

TABLE 13

TABLE 14

SOME COMMON IMMISCIBLE OR SLIGHTLY MISCIBLE PAIRS OF SOLVENTS 34

PREDICTED EFFECT OF PRESSURE ON BOILING POINT 36 PREDICTED EFFECT OF PRESSURE ON BOILING POINT 37 HEATING BATHS 38 WHA TMAN FILTER PAPERS 38 MICRO FILTERS 39 COMMON SOLVENTS USED IN RECRYSTALLISATION 40 PAIRS OF MISCIBLE SOLVENTS 40 MATERIALS FOR COOLING BATHS 41 LIQUIDS FOR STATIONARY PHASES IN GAS

CHROMATOGRAPHy 4 METHODS OF VISUALISATION OF TLC SPOTS 42 GRADED ADSORBENTS AND SOLVENTS 43 REPRESENTATIVE ION-EXCHANGE RESINS 43 MODIFIED FIBROUS CELLULOSES FOR ION-EXCHANGE 43 BEAD FORM ION-EXCHANGE PACKAGINGS 44

LIQUIDS FOR DRYING PISTOLS 44 VAPOUR PRESSURES (mm Hg) OF SATURATED AQUEOUS SOLUTIONS IN EQUILIBRIUM WITH SOLID SALTS 45 DRYING AGENTS FOR CLASSES OF COMPOUNDS 46 STATIC DRYING FOR SELECTED LIQUIDS (25°C) 46

SOLUBILITY COEFFICIENTS OF AIR AT 1atm IN WATER 48 SOLUBILITY COEFFICIENTS OF O2 AT 1atm IN WATER 48 BUNSEN COEFFICIENTS (~) OF GASES AT 1atm

OSTWALD COEFFICIENTS (l)/L OF O2 AT 1atm

IN AQUEOUS SOLUTIONS AT 25°C 49 SOLUBILITIES OF HCI AND NH3AT 760mm (g/lOOg OF

BOILING POINTS OF SOME USEFUL GASES AT 760 mm 50

TABLE 15

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TABLE 19

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TABLE 21.

TABLE 22

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TABLE 25

TABLE 26

REMOVAL OF TRACES OF METALS FROM REAGENTS 61

Removal of other metal contaminants 63

Salts 65

NITRO COMPOUNDS 76

PURIFICATION OF ORGANIC CHEMICALS

(Including Organic compounds of B, Bi, P, Se, Si, and ammonium and metal salts of organic acids)

MISCELLANEOUS COMPOUNDS (including biologically useful reagents,

Low-molecular-weight bioactive substances, antibiotics, coenzymes, vitamins,

lipids, phospholipids, nucleosides, nucleotides and polynucleotides) 662