Drying Agents / Cooling Mixtures / COD Determination

Drying Agents for Solvents

Key for Drying Agents
1 Calcium chloride, fused    C/1360,C/1400,C/1480  
2 Sodium sulfate, anhydrous    S/6600, S/6640  
3 Phosphorus pentoxide    P/2960, P/3000  
4 Potassium hydroxide    P/5560, P/5600, P/5640  
5 Potassium carbonate, anhydrous    P/4080, P/4120  
6 Magnesium sulfate, dried    M/1100  
7 Calcium oxide    C/2120,C/2160,C/2100  
8 Barium oxide    - 
9 Sodium    S/1920  
10 Calcium    C/0840  
11 Magnesium    M/0050, M/0100, M/0200
12 Magnesium perchlorate    M/0950  
13 Copper (II) sulfate, anhydrous    C/8600  
14 Molecular sieve 3A    MS/1010  
15 Molecular sieve 4A    MS/1020  
16 Distillation     
17 To freeze out     
 Solvent Agent    Drying Agent    Solvent Agent    Drying Agent  
 Acetic acid   3,12,13,17    Ethylene glycol monomethyl     
 Acetic anhydride   1  ether   16
 Acetone   1,5,14    Formic acid   3,12,13,17  
 Acetonitrile   1,3,14    Furfuraldehyde   1,15
 Acetylacetone   1,5,14    n-Heptane   1,15
 iso-Amyl alcohol   5,16  Heptan-2-one   1,5
 Aniline   4,8  n-Hexane   9,14
 Benzene   1,9,15,16    Iodoethane   1,15
 Benzyl alcohol   4,6,7,15,16    Methanol   1,7,11,14  
 Bromoform   1,15  Methyl iso-butyl ketone   1,5
 Butan-2-ol   5,16  Methyl acetate   5,7
 iso-Butanol   5,16  n-Pentane   9,14
 tert-Butanol   7,17  Pentan-1-ol   7,11
 1-Butanol   5,16  Piperidine   4,8,15  
 n-Butyl acetate   6  Propan-1-ol   7,11
 tert-Butyl methyl ether   14  Propan-2-ol   7,11,14  
 Carbon disulfide   1,3  Propylene carbonate   16
 Cyclohexane   9,15  Pseudocumene   1,9,15  
 n-Decane   1,15  Pyridine   4,8,15  
 1,2-Dichlorobenzene   1,15  1,1,2,2-Tetrabromoethane   1,15
 1,2-Dichloroethane   3,15  Tetrachloroethylene   2,5,15,16  
 Dichloromethane   1,15  Tetrahydrofuran   4,9,15  
 Diethyl ether   1,9,15    Tetrahydrofurfuryl alcohol   2,6
 Di-iodomethane   1,15  1,2,3,4-    
 N,N-Dimethylformamide   15,16  Tetrahydronaphthalene   1,9
 Dimethyl sulfoxide   16  Toluene   1,9,15,16  
 1,4-Dioxane   1,9,15    Tributyl phosphate   18
 Di-iso-propyl ether   1,9,15    Trichloromethane   1,3,15  
 Ethanol   7,11,14    1,1,1-Trichloroethane   1,3,15  
 Ethyl acetate   3,5  Trichloroethylene   2,5,16  
 Ethyl acetoacetate   3,5  1,1,2-    
 Ethyl methyl ketone   1,5  Trichlorotrifluoroethane   1,3,15  
 Ethanediol   2,16  2,2,4-Trimethyl pentane   9,15
       Xylene   1,9,15,16  

Cooling Mixtures

 Mixture    Temperature °C  
 20% Potassium chloride    –12  
 50% Ammonium nitrate    –15  
 33% Sodium nitrate    –24  
 23% Ammonium chloride    –3  
 25% Sodium chloride with crushed ice    –21  
 62% Calcium chloride 6H2O with crushed ice    –39  
 59% Calcium chloride 6H2O with crushed ice    –55  
 Methanol or acetone and solid carbon dioxide    –77  

C.O.D. Determination

Methodology

For samples with <400mg/L C.O.D., the following methodologies can be applied.
If C.O.D. is >400mg/L, then dilute accordingly and use a 10mL aliquot.

1977 Method

Don't use grease on glass joints!
1. Pipette 10mL of sample (or diluted sample) into a 150mL boiling flask
containing clean washed anti-bumping granules.
2. Add, by pipette, 1mL of 20% Mercury (II) sulfate (J/5100), mix well.
3. Add 18.5mL of Ficodox (J/4000) and mix well.
4. Fit the condenser and boil gently, under reflux, for 2 hours + 10 minutes.
5. Cool and add 25mL of distilled water via the condenser.
6. Disconnect the flask, cool to 25°C under running water, add 1-2 drops of Ferroin
indicator, and titrate excess Potassium dichromate with the standardised
Ammonium iron (II) sulfate. End point is indicated by a change from blue/green to orange.
Carry out a blank determination on all reagents replacing the sample with 10mL of distilled water.

1986 Method

As per the 1977 method but with the following changes:
Step 2. Add, by pipette, 0.6mL of 1,000g/L Silver nitrate solution (J/7380), 0.4mL of distilled water, mix well and leave to stand for 2 minutes.
Step 3. Add 18.5mL of Ficodox Plus (J/4010) and mix well.

Calculation of results

C.O.D. = 800M (VB-VS)xD mg/L
Where: M = Molarity of standardised Ammonium iron (II) sulfate solution
VB = Volume of Ammonium iron (II) sulfate solution required for the blank
VS = Volume of Ammonium iron (II) sulfate solution required for
the sample
D = Dilution factor (1 for undiluted sample)