Seawater Composition and Salinity :: Tides and Salinity

Using the decanted supernatant solution from the precipitation experiment, a wire loop was dipped into the solution. This loop was stuck in the flame from a Bunsen Burner and heated until a flame appeared. The presence of a bright yellow flame confirmed that Na+ was in attendance. Using a cobalt glass as a filter, the loop was examined and a violet flame was present, showing that K+ was also in the supernatant solution. Testing for NH + This test was carried out using the original solution to avoid contamination of ammonium salts from the other procedures. 0.1M NH4CL and DI water were added to a large well on the micro drop tray before drops of 6M NaOH were added. A piece of red litmus paper was put on top of the well and covered with a watch glass. The appearance of an unmarked blue color, a direct result of the release of NH3 gas, on the paper confirmed the existence of NH4+. The experiment was repeated using seawater instead of the 0.1M NH4CL and DI water combination. ! Quantitative Pre-Gravimetric Set Up Test tubes were obtained and labeled using a bl according to which test the sample was intended for Barium) and what depth the sample was obtained at or bottom).All the test tubes were put in a beaker and an oven at 110˚C for half an hour to dry. Once dry th removed and allowed to cool on a test tube rack, as Figure 1: Test tube rack with test tubes Figure 1, before being weighed and their weights rec Silver Halides Gravimetric Analysis The tests tubes labeled ‘Halides Top’ and ‘Halides Bottom’ were taken and 1mL of seawater was added to each. The test tubes were then weighed and their new weights recorded, before 6M Nitric Acid (HNO3) was added to each to acidify it. 0.1M Silver Nitrate (AgNO3) was introduced, causing a white precipitate to form. The solution was stirred with a glass rod and centrifuges for approximately a quarter of an hour. Once complete, another series of drops of 0.1M AgNO3 were added to ensure complete precipitation and the solution was recentrifuged for several minutes. The supernatant solution was decanted into a wast container and DI water was mixed into the precipitate to clean it. The solution was centrifuged, supernatant decanted, and rinsed with DI water once more before being centrifuged and the aqueous solution decanted for a final time. The test tubes were then returned to the beaker and placed back into the oven to dry for a week.