USC Dana and David Dornsife College of Letters, Arts & Sciences

Our hard work for the past week, gathering data and samples finally paid off with some time in the lab. Lisa came out for the day to help us begin to prepare our samples for the analysis we will do later in the week. The morning consisted of sieving our soil samples through 2 mm screens, allowing us to remove unwanted rocks and organic material in addition to breaking up the clumps of soil that were too large to fit through.  From our large samples, we labeled weigh trays and took 100 mg of the sample. We placed 10 samples and 3 duplicates into erlenmeyer flasks and added 50 mL of milliQ water. We also created a blank flask filled only with milliQ water and another flask with stock solution comprised of 5 mL NH4(SO4)3 with 45 mL milliQ. We added 3 grams of Potassium Persulfate to each flask, covered the flasks with aluminum foil, taped the aluminum foil on with autoclave tape, placed them into pyrex trays and then put them in the autoclave for 2 and a half hours.

While we waited for the autoclave cycle to run we prepared our analytical mixtures. We had made a good amount of our stock solution which was placed into the explosion-proof refrigerator in the Wrigley Lab.  I had the task of weighing out 39.6 g of sodium salicylate and 0.026 g of sodium nitroferricyanide (III). Sabrina and Alex set about fashioning a funnel out of waxy weigh paper and tried to get this flour-like compound into a 100 mL volumetric flask.  Miller then helped me weigh 25 g of sodium citrate and 4.6 g of sodium hydroxide which required careful funneling, as we were using weigh paper, into a 250 mL volumetric flask.  Once our mixtures were in the flasks we added milliQ water and shook, then took turns shaking and then shook more. The 250 mL solution mixed easily, but the 100 mL formed a hard pack which required the majority of our time and shaking energy to dissolve. Once they were finally a homogeneous mix, we transferred the solution from the flasks into sealable glass containers which we put into the fridge with our stock solution.  We then waited a few more minutes for our samples to finish in the autoclave, removed the samples and placed them into our designated lab space to begin our analysis on Thursday. The lab work, while not physically taxing like most of our work out here, was meticulous and time consuming, leaving me quite tired by the end of another long day.

For more pictures, check out today’s photo album: Day 37 Lab Work Part II