By: Howard Andres

In this experiment of paper chromatography, our lab group’s purpose was to separate a mixture of metallic ions in solution and determine which ions were present in an unknown mixture by comparing them with the colors produced by individual ions that could be present in the unknown mixture.  By allowing the solvent to separate the ions on the paper, and observing the position and color of the spot produced by each ion, and the positions and colors of the spots produced by the unknown mixture containing some of those ions, we would be able to determine the ions present in the unknown.

After the solvent had already run its course of separating the ions through the paper, and before the paper was sprayed with the staining reagent, not to many observations could be made.  Without the staining reagent, it was somewhat noticeable of how far the solvent went up the paper, because after the paper dried little bumps, showing that area used to be wet,  going up the paper showed how far the wet solvent went up.  The solvent covered about three-fourths of the paper, and basically the only color visible was a yellow spot in the section of the paper reserved for Fe³⁺.  After the staining reagent was sprayed though, the color of each ion appeared throughout the paper, with each color of each ion recorded in the data and calculations page.

The distance the solvent and each ion moved up the paper is also recorded in that section, as well as their R_f values.

After finding out which color each ion had, we were able to compare them with the ions that were in the unknown mixture.  Our group noticed that the colors present in the unknown were about the same as the colors made by the Co²⁺ and Cu²⁺ ions, which were purple-brown and tan, respectively.  With this information, we concluded that the unknown mixture contained the Co²⁺ and Cu²⁺ ions.

Our experiment went pretty well, but there were probably a few errors.  One was that the distant the solvent moved up the paper should have been equal throughout the whole paper, which was about 6.3cm throughout most of it, but at the end of the paper, after the area reserved for the unknown, the solvent moved all the way the paper.  This is probably okay though since the unknown was the last listed on the paper, but it probably should still be noted.  Additionally, the R_f values in the unknown should have been about the same as those for the individual ions.  This was true with the Cu²⁺ ion, with it having an R_f value of 3.3cm/6.3cm as compared to its R_f value of 3.4cm/6.3cm in the unknown.  The R_f value of the Co²⁺ ion was 5.2cm/6.3cm though, a somewhat wide difference when compared to its R_f value in the unknown, which was 3.4cm/6.3cm, meaning that is a possible error.  Overall though, the experiment with paper chromatography went pretty well.

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