Week of 12/5-12/11

Updates have been thinning out from all of our teams… remember to post EVERY week! Even if it’s just to say you didn’t have a meeting.

Beckman has decided they will do a quick experiment to test the effects of using UV light (ie ozone cleaning) on their plates before spotting. They will be using iron nitrate as a control and varying the amount of time left in the germicidal cabinet with the UV light from 5 min up to 1 hour. This will allow them to leave plates in the cabinet as short amount of time as possible while still getting the benefits of reduced coffee rings. This info will also be useful to other schools who have such a cabinet and wish to do the same technique.

San Marino’s Blank team made a new plate this week once again using Cu(NO3)2 and ZnSO4. Control of Fe(NO3)3. Spot ratios (Cu:Zn) are 10 to 0; 7.5 to 2.5; 5 to 5; 2.5 to 7.5; and 0 to 10.

Green team has 2 updates. They remade the plate with Fe3+, Ce3+, and Co2+, from 11/14. Along with the ratios shown below, they also added 3 spots of Cu(NO3)2 and 2 spots of CuCl2.  It was fired at < 450℃. 

Spot Fe3+ Ce3+ Co2+
1 0 0 100
2 0 100 0
3 100 0 0
4 50 50 0
5 0 50 50
6 50 0 50

 Upon testing, they found the two highest peaks corresponded to 100% Fe3. Usually, the Fe3+ control spot returns a light blue color, as it did at the beginning of the season. The fact that it was a darker color this time may indicate that a subpar material on one portion of the plate is impacting the performance of other spots. Changing the applied voltage from 0.05V to 0.1V depressed the peaks across the board. 

They explain these results in the following manner: “As usual, the dark current was measured before each scan. It remained stable and below 0.5V, but we discussed that these checks don’t tell us everything. Corrosion and/or oxidation could be occurring on other parts of the plate. Essentially, there may be one or more “bad” materials on the plate that are acting as voltage leaks. Relative to the applied potential of our plate, they are “downhill”, meaning that any spike in current is hidden. Instead of jumping above the water splitting potential and releasing “downhill” to generate a current, it goes “through” the leak. Because the plate measures the difference in current when light is shined on a spot, a material that acts as a “leak” while in the dark can influence the spot being tested. One compelling fact is that even though our baking and testing proceeded without a hitch, we still got subpar results. In addition to our strange iron control spots, the Cu2+ spots on the side were not reaching the yellow/green range. The current leak concept is a possibility because it reveals why electrical activity may be masked. Next Monday, we will strive to eliminate the “bad” material combination, possibly by spotting multiple plates.”


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