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)