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Week 4 - Once Again, Almost Up and Running

This week was a short week due to Independence Day and a field trip, and the week was mostly spent trouble-shooting. On Monday, we tried something new to be able to read the 4-chloroaniline concentration on the HPLC. Our conclusion as to why we were seeing no 4-chloroaniline in our HPLC output was that the aniline was adsorbing to MnO2, so when we filtered out the MnO2, we also effectively filtered out the 4-chloroaniline. Ali talked to a researcher at her conference who, rather than filtering the MnO2, dissolved it in ascorbic acid, thus freeing the 4-chloroaniline for detection by the HPLC. I attempted this, and saw that the MnO2 clearly did dissolve. Unfortunately, when I ran the aliquot on the HPLC, the spike from the ascorbic acid was so large that it completely obscured the spike from the 4-chloroaniline. Alas, we had hit another snag.

On Tuesday, Vanessa took all of us interns on a trip to the Bonneville Dam, so no further progress was made in terms of experiments. It was neat to see how the dam functioned, and we even got to go stand on the giant turbines. I enjoyed trying to see where my engineering knowledge was sufficient to explain how the dam worked, and in what ways I was completely clueless.

On Wednesday, I spent most of the day dealing with MnO2 synthesis. So far, we had been synthesizing MnO2 in small batches with the correct concentration for our experiments. However, it would be great if we could simply create a large batch, because the synthesis process is fairly time-consuming. Unfortunately, creating a large batch meant we could not centrifuge the synthesis container, and settling took an extensive amount of time for the MnO2. Paul has always been wary of centrifuging anyways, as it might encourage clumping and morphology differences, so we consulted with people from Dr. Tebo's lab who are also working with manganese oxides. They pointed us to an extensive paper on manganese oxide synthesis, and so we are considering changing our procedure.

On Thursday, I tested mixing our MnO2 with lower concentrations of acetic acid to see if it still dissolves. I found that even at concentrations with much less excess ascorbic acid than we initially used, most of the MnO2 still dissolved quite quickly. However, there were still noticeable particles that took time on the vortexer to dissolve. Ali and I will have to run additional tests and consider whether the quick dissolution of most of the MnO2 is fully quenching the reaction with 4-chloroaniline.