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***Update Some questions I am considering to try to answer this question;

  • When dissolving the powder in acetic acid, which ions are present?
  • From what I've read, I haven't found any acetate salts that are not soluble in water. What other metal salts could be forming that aren't soluble?
  • Which ions might be present in the rock that would not readily react with the acetic acid?
  • What would be a good compound to replace the acetate ion in a double replacement reaction such that the resulting metal salt would precipitate out of solution?
  • Are metal acetate salts prone to reaction with oxygen? Are the metal ions in the acetate salt more attracted to the oxygen or the acetate ion? (i.e. will my sample 'rust'?)

I am leaving the main question as-is, posting this update because asking questions is part of my problem solving process.


I was experimenting with the (air) dried residual powder residue left over from cutting this rockslab of rock cut off with tile sawin my wet saw in an attempt to determine the composition of the metallic components of the rock I was working with. The rock appears to be a crystalline silicate rock of some variety. It has minimal to no reactivity with concentrated HCl in its raw form. The geology of the area indicates it was once shallow ocean, with lots of limestone and cryptocrystalline quartz and crustaceous fossils in the surrounding area. The compound in questionenter image description here was created by soaking the residual powder in 7% white vinegar (acetic acid) for several days with constant stirring. The remaining solution was separated under vacuum filtration and residual solid was again left to air dry for several days. After several days I noticed that the top layer of the filtrate had turned brown with blue splotches. The bottom layer was white with bright blue speckles mixed in. % isopropyl alcohol I scraped off the top layer and set aside for solubility tests. It was nearly insoluble in and soluble in water. When the mixture dissolved in water, it turned yellow.after about 20 seconds in water, you can also see the "blue speckles" in the white compound

My hypothesis was that the blue compound was copper acetate, the dark brown solution is iron(II) acetate and the yellow in solution is an iron/copper coordination complex. I also suspect there is aluminum in the rock as a USGS survey indicated the presence of muscovite in the region and calcium due to the abundance of fossilized sea shells and limestone. Though I may be completely wrong. I would love if anyone could shed some light on this for me or point me in a different direction for determining the trace elements in the rock.

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  • $\begingroup$ Many university geology depts have instrumentation to do elemental analysis $\endgroup$ – Andrew Feb 5 at 21:00
  • $\begingroup$ I would like to find an answer that uses chemistry more so than postal mail :) With that in mind, I was thinking about dissolving the solution again and separating with column chromatography, then recrystallizing and trying to use some algebra (partial fraction decomposition) to determine the composition. $\endgroup$ – XisUnknown Feb 16 at 3:19
  • $\begingroup$ If you have a relatively pure sample and access to reagents, there are many flowcharts available online for "qualitative analysis of cations" that provide systematic methods for distinguishing common cations from one another. That's how they did it in the days before mass spec. $\endgroup$ – Andrew Feb 16 at 13:35
  • $\begingroup$ @Andrew Can you provide any such flow charts? I've looked in a couple of texts but came up short. The closest I've come was my old chm lab manual for determining an unknown salt, but the info there was specific to the salt in question and isn't comprehensive. $\endgroup$ – XisUnknown Jul 21 at 14:57
  • $\begingroup$ Here’s one example: chem.libretexts.org/Bookshelves/General_Chemistry/…. A basic internet search will turn up other variations $\endgroup$ – Andrew Jul 21 at 16:02

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