Chemical Oxygen Demand Lab Report

We then added 10cm3 ethanoic anhydride to the salicylic acid and swirled the contents, this mixes together the two chemicals. We then added 5 drops of concentrated sulphuric acid to the flask and thoroughly swirled the mixture, this creates the solution that makes the aspirin. We then warmed the flask for 20 minutes in a 400cm3 beaker of hot water which was approximately 60°C, we made sure the flask did not go above 65°C because this could have caused the contents to evaporate. Part 2: Using a 25cm3 measuring cylinder we measured out 15cm3 of ethanol into a boiling tube and then prepared a beaker half filled with hot water at approx. 75°C, we got this temperature by filling the beaker with cold water and slowly adding boiling water from a kettle until we reached the right temperature.

Then, we did reflux for 75 minutes. After reflux, we removed the reaction mixture from the apparatus and cooled it for several minutes. We transferred the mixture to the beaker that contained water (30 mL). We cooled the mixture to room temperature and added sodium carbonate to neutralize the mixture. We added sodium carbonate until the pH of the mixture was 8.

Rinse a 250 ml volumetric flask with deionized water. 7. Label the volumetric flask so you know which solution is in it. 8. Place a clean funnel into the mouth of a 250ml volumetric flask.

Heat the solution until it is at 100 ˚C then continue heating for 75 minutes. Evolution of CO2 and NH3 is observed during heating. e. After 75 minutes of heating, stop stirring. Draw a little clear solution with a pipette, cool the solution to room temperature and measure its pH value with pH paper. when the pH is 7, allow the solution to cool to room temperature.

5 mL of 3M sodium hydroxide, 5 mL of de-ionized water, and 15 mL of hexane were added to the reaction flask and stirred. The mixture was transferred to a separatory funnel, separated into an organic layer and water layer, and then drained. The water layer was washed twice with 10 mL of hexane. The organic layer was dried

Throughout the mixing process, the clear red solution slowly changes to a denser red solution (Appendix figure 23). A thermometer was used for temperature checking. The beaker was removed from the hot plate when the temperature was found to be higher than 50 ℃. This was done to prevent a sudden gelation happen before all the active dissolved in the ethylene glycol. Moderate heating of the solution for a period of time is allowed to obtain a wet gel (Appendix figure 24).

The mixture was finally made upto 5 mL with distilled water and placed in hot water bath at 95ºC for 1 h. After cooling, 1 mL of distilled water and 5 mL of the mixture of n-butanol and pyridine (15:1, v/v) was added. The mixture was vortexed and after centrifugation at 4000 rpm for 10 minutes, the absorbance of the organic layer (upper layer) was measured in UV-Vis spectrophotometer (Shimatzu) at 532 nm against blank using distilled water. TBA when allowed to react with MDA aerobically formed a colored complex [MDA-(TBA) 2 complex] which was measured with spectrophotometer. MDA concentration (measured as TBARS) was calculated as

Once a prevalent color change had been observed at approximately 4 minutes (blue green color) the crucible was set on the counter using the tongs to cool for approximately 5 minutes. The appearance after this period resulted in another color change back to white. The crucible, lid, and hydrated copper sulfate was weighed again to calculate the mass of water lost by dehydration (described in table 1.3). This was done by subtracting the final mass by the initial mass of the crucible, lid, and compound. The mass of the crucible would remain unchanged while the mass of the compound would be altered.

First, 50 mL of the sample was placed into a 250 mL Erlenmeyer flask, and onto a stirring plate. Then, the pH of the solution was measured and adjusted to be within the range of 4 and 6, using nitric acid and sodium hydroxide. After the pH was optimal for the experiment, a single mL of indicator- acidifier reagent was added to the sample. Then, 50 mL of mercuric nitrate was place into a burette and titrated with the sample until the color of the solution turned from blue to purple. The volume of titrant used for the reaction to reach endpoint was recorded.

It was then washed off with ether after the drying process was finished and allowed 5-10 minutes for the drying of the ether solution. ?M HCl was added drop wise to tube 2 to neutralization, while testing the solution with litmus paper. A boiling stick was then added to the tube and heated cautiously to bring most of the solid carboxylic acid into solution. The tube was then allowed to cool slowly to room temperature then cooled in ice. The solvent was removed and the residue recrystallized from boiling water.