We've found out the reason why two layers form on our oil, and the reason behind the solidifying of our oil. To explain this, we need some background information on the components inside oil.
The rambutan seed oil here consists of different fatty acids. Fatty acids are critical components found in oil.
There are saturated and unsaturated fatty acids. A saturated fatty acid does not have any carbon-carbon double bonds, and hence its chemical structure is rigid. This rigid chemical structure causes the common saturated fatty acid to be in solid form. An unsaturated fatty acid consists of carbon-carbon double bonds and as such its chemical structure is bent. Unsaturated fatty acids are commonly liquid as their structures are not rigid.
However, these fatty acids do not exist in this pure form. If they do exist as just fatty acids in the oil, they would be Free Fatty Acids (FFAs). However, in normal ambience form of oil, there's very little FFAs. Three of these fatty acids combine together with glycerol to form a triglyceride.
These triglycerides could consist of any combination of three fatty acids (denoted by R', R'' and R''') here. Going back to saturated fatty acids, if these saturated fatty acids form saturated triglycerides, these triglycerides would have rigid structures, being in solid form. However, more unsaturated triglycerides would be more liquid-form.
This explains why our oil tends to have solid particles settling. Saturated triglycerides are forming, triglycerides get more rigid in nature, forming solid particles. Saturated FFAs also contribute to this.
Due to this, we have to reheat our oil before we are able to use it again. We reheated at about 50-60 degrees celsius.
After which, we are able to find out the oil's properties.
Volume of oil = 9.4 mL
Mass of oil = 3g
Density of oil = 0.319 g/mL
Yield of oil by soxhlet extraction = Mass of oil/Mass of seeds = 3g/101.37g = 2.96%
The reason for our low yield is because we realised a few mistakes we did when preparing the crushed seeds. We dried it at 1100C for 20 minutes. We should have dried it at a temperature lower than 80 degrees celsius, or else the oil content in the seeds would also be dried up. There was a high probability that a significant portion of the oil content was already dried up when we tried to dry the seeds.
Another possible reason for this low yield is the soxhlet extraction was run only for 6 cycles. We had a shortage of time due to Christmas break and also New Year's so we stopped at 6 cycles. The average rate was 1 to 1.5 cycle per hour.
A higher number of cycles would generate more oil from the seed stack.
An appropriate number of cycles we should do for soxhlet extraction should be 20.
We also conducted a flammability test and it was successful, the oil burnt readily, signifying that the oil is of good quality since it is flammable. The oil was put on a fiber wick and it was lit up, and the oil caught fire and continued to burn even after we disposed it into the drain.
When we vacuum filtrated and distilled ethanol out from the ethanol and bio-oil mixture from the round-bottomed flask, we only got a small volume of oil.
To prove its true suitability of yield in generating bio-oil from rambutan seeds, we need to re-do the drying and the soxhlet extraction.
However, we searched around in Clementi, Woodlands, Yishun, Jurong, Bedok, Tampines, and Naeem even asked his relatives in JB, Malaysia if there was any rambutan fruits growing but we all got the same answer, 'It's not in season right now'. We should've bought more back in December.
We were disappointed by this. Nevertheless, lets just carry on with what we have!
COMING UP: PREPARING FOR THE LONG AND ARDOUS TRANSESTERIFICATION!!!
STAY TUNED
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