Rock On
Hello everybody,
My name is Martin and I’m a sophomore from Belmont, MA. While the lab seems to be invaded by a variety of creatures this summer, I had the foresight to decide to intern at a lab off campus. Thanks to a KINSC Summer Stipend, I am spending my summer in David Johnston’s lab at Harvard University in Cambridge, MA doing some biogeochemsitry. Avid followers of the blog will notice that Emily worked in the same lab last summer with her aptly named post Summer Rocks. For a few more facts about me and Haverford: I play Ultimate Frisbee for Big Donkey Ultimate, and play upright bass in various ensembles on campus.
In my work this summer, we are analyzing shale rocks from a few sites in Utah to determine the sulfur, iron and carbon compositions of the rocks. The work is supervised by Ben Gill, a post-doc in the lab. Our goal is to determine the environment of the ocean at the time the rocks came from and figure out why it was that way. These rocks are from the early Cambrian era (about 500 million years ago). After spending the first few days becoming friends with the shatterbox, the first methods I used to analyze the samples was CRS, which extracts Chromium Reducible Sulfur. This method is a great example of Redox chemistry at work. After adding HCl to the sample to release the carbonate, a solution of CrCl2 (blue) is added and nitrogen gas is bubbled through. Over the course of two hours, the chromium is oxidized, turning green, and the sulfur in the rocks is reduced and is liberated as H2S which is then captured in a zinc acetate solution as ZnS. Then by adding Silver Nitrate, we have a precipitate that can be filtered out and analyzed in the mass spec to determine which sulfur isotopes are present.
The most popular man on campus, John Harvard, makes hundreds of new friends daily. And look at those shiny shoes!
The Chromium chloride starts out as a blue solution...
Adding Chromium Chloride
and 2 hours later it is oxidized and a greenish solution
