We explored the ECD patterns formed by using equimolar solutions of silver nitrate, zinc (II) nitrate, and aluminum nitrate as the electrolyte, using copper electrodes in each solution. We also explored the effects of the nature of the electrode on the deposition patterns. Since an electric field exists between the two electrodes, it seems that if the cation charges are different, +1, +2, and +3, then the forces which attract a cation to the cathode should differ, causing a different fractal pattern. If the charge of the ion is greater, then the pattern will form quicker, have a larger velocity, and have a greater dimension.
Our investigation consisted of two trials. For trial I, to ensure that each cell had the same voltage we set up three ECD cells in parallel (15 volts). The cells contained 0.2-M solutions of silver nitrate, zinc (II) nitrate, and aluminum nitrate. The electrodes were copper electrodes. After one run, we decided to do each cell separately, since we wanted to record data for each run. (In addition, it was fairly confusing with all the wires we had in our setup.) We weighed the anode for each trial before the run and then after the run. We determined the fractal dimension of each using the spreadsheet process. Next we obtained the image of each of these patterns with the camcorder, and then used both the box method and the circle method, of the Fractal Dimension program, to determine the fractal dimension of each pattern.
For trial II, we used silver electrodes with silver nitrate solution, copper electrodes with copper(II) nitrate solution, and aluminum electrodes with aluminum nitrate solution. We did each run with 15 V and 5 V. We used the following materials in this experiment:
3 ECD cells , ammeter, 0.2-M zinc nitrate, voltmeter, 0.2-M silver nitrate, copper wire-for electrode, 0.2-M aluminum nitrate, 3 plastic radius templates, aluminum wire-for electrode. silver wire- for electrode zinc wire for electrodes, gloves, goggles, scanner, or camcorder, mettler balance sensitivity = 0.001 g, 3 candy bars.
During this investigation, we observed the formation of aggregates around the cathode, as shown in figures 1-5. When we tried using aluminum nitrate with aluminum electrodes, and with copper electrodes, no aggregate formed, but we noticed the formation of bubbles around the cathode. We also tried using chromium (III) nitrate solution and bismuth (III) nitrate solution, and observed the same formation of bubbles. When we tried using copper(II) nitrate, we observed a beautiful pattern developing; however, we noticed the formation of gas bubbles in the aggregate that had formed. (See figure 1) This indicates, to us, that the aluminum, chromium, and bismuth require more energy for formation than does the nitrate ion. Possibly, the nitrate ion is breaking down into nitric oxide (NO). Our data is summarized in the following table:
|Time (sec)||Current (mA)||# of atoms||Radius (cm)||Velocity (cm/sec) [Ave.=0.04]|
|Time (sec)||Current (mA)||# of atoms||Radius (cm)||Mass (Grams) [total = 0.04662222]||Velocity (cm/sec) [ave = 0.00386905]|
A summary of our data is as follows:
|Solution Type/Voltage||Fractal Dimension (BOX)||Fractal Dimension (CIRCLE)||Velocity (cm/sec)|
|Copper II Sulfate/15V||1.25||1.09|
|Zinc Nitrate/5V||no data collected|
|Aluminum Nitrate/5-15V||no data collected|
|Chromium (III) Nitrate/5-15V||no data collected|
|Bismuth (III) Nitrate/5-15V||no data collected|
This data indicates that the greater the positive charge on the cation, the greater the velocity. This observation is based on a very limited data set, namely zinc ions and silver ions. In addition, the data indicates that the +3 ions have a much greater electrical potential than do the nitrate ions. This prevented us from obtaining any numerical data.
Following our experiments and data analysis, we feel that, based on our limited results we are unable to confirm that our hypothesis is true. We did have some support for our hypothesis; namely, for the two cases for which we determined velocity, the cation with the greater charge had the larger velocity. More testing would be necessary for confirmation. We did observe distinct differences in our testing of the compounds containing nitrate ions. We speculate that when one uses nitrate ions, gases, which disrupt the formation of the aggregate, will form. In summary, our results leave our hypothesis unconfirmed.