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Solubility book (3rd Edn)
Examining the effect of temperature on the solubility of vanillin in ethanol and methanol
There were some noticeable differences in the solubilities of vanillin between EXP207 and JennyHale1. It would be interesting to find out whether any difference in solubility occurs when the measurements are carried out at different temperatures. (
Good idea. JCB
) It is possible that the two experiments, though carried out in the same lab, were carried out at different temperatures due to the natural fluctuation of temperature in the lab. To investigate this, I am taking a sideways approach to the main task for a short while to carry out the solubilities at different temperatures to investigate the effects. I have chosen vanillin as I have a large supply available, and it is quite soluble to allow good results with less errors to be gained.
12 eppendorfs were taken and split into two groups of 6. Group 1 were labelled with the planned contants and group two were labelled and weighed. Three eppendorfs from group 1 had 750 µL of ethanol added and the remaining three had 750 µL methanol added. One ethanol and one methanol eppendorf were kept at room temperature, one each of a methanol and ethanol filled eppendorf were stood in heat blocks set to 30 and 40°C. The room temperature was measured as 23°C by holding a thermometer in the air until it settled.
Vanillin was added to each eppendorf and the eppendorfs inverted several times (
can you provide more detail about this method by video or text - is this shaking or very slow turning? JCB
) to dissolve contents.
Eppendorfs are tipped up end on end. I held the lid and the base between my finger and thumb and turned wrist from side to side about 1 turn from end to end and back per second.
The eppendorfs at 30 and 40°C were put back in the heat blocks after each inversion to keep the temperature as close as possible to the desired temperature. This process was repeated until all solutions were saturated. (
I think you need to include how much time is involved here and how much mixing took place - I am starting to suspect that differences in solubility may be related to the kinetics of dissolution. In other words, you may not have a saturated solution without prolonged vigorous mixing. That can be tested in a separate experiment too using different vortexing times. JCB
) The solutions were not centrifuged. (
Do you have a pic to show clear separation of the supernatant? JCB
500 µL of each solution was added to its corresponding group 2 eppendorf and the eppendorfs placed in the speedvac to dry. The heater function was not used.
The results will be added to this spreadsheet as they are found out
I will answer JCB queries asap, but I don't have my camera in labs today. Can photograph and video technique tomorrow and then upload. My apologies, had my laptop been in full working order I could have used my mobile phone, done it now and transferred by bluetooth. However no other blue tooth computers in area and mobile has no usb cable.
Camera battery has died before I''ve even started. I will repeat this experiment on Monday complete with video and photos. In the meantime I have tried to describe in my experimental what I did more accurately.
This experiment shows some evidence of a correlation of temperature and solubility (
copy the graph in the spreadsheet directly into the wiki for convenience - just upload as an image JCB
), but not enough evidence for me to state categorically that temperature plays a role. The spreadsheet has been updated with the concentrations that I calculated and a graph of those concentrations against temperature. I want to try and repeat this experiment on Monday to see if I can replicate my results and to address the concerns about solubility given by JCB.
How long did leave the solutions to equilibrate? Taking that into account, compare your results against those previously reported at room temperature. Use the Web query on the list of experiments page. JCB
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