Tuesday, July 6, 2010
Unfortunately, the spectrometer ran out of nitrogen over the long weekend and we won't be able to replace it for a few days. This means I have to put off testing for a few days, but it also gives me time to look at the results that I have so far and plan the next set of tests. Today I worked on finding the uncertainties for all of my data and seeing how they compare to the theoretical Poisson-Boltzmann prediction. A few things bother me about the final fit that I came up with, which is seen above. First of all, PB theory would suggest that there should never be more than 1 total charge being compensated for, which there often is. Second, the eighth and tenth data points are disturbingly large. Third, the error bars for only the eighth and tenth points can be seen on the graph, meaning they are by far the largest errors. Fourth, the PB predicted curves shown on the graph as "Theoretical" had to be translated to fit that well on the graph. The Cohex curve had to be multiplied by a factor of 1.25, and the Mg curve had to be multiplied by a factor of 1.6. This means that my results are systematically higher than they "should" theoretically be. Also, I believe that once the new nitrogen comes and some maintenance is done to machine, combined with the new calibration standards I will make tomorrow, the results be more precise. This should help identify where the problems are coming from. Also, I should say that the third trial I ran, which is identical to the fourth I have yet to run, was prepared slightly differently and has already shown to be more accurate.
Posted by jgiannini at 5:01 PM