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)