Ink Essay

1080 Words3 Pages

To identify inks of similar color from one another from mere observation is near impossible since colors can look identical to the human eye while differing in composition. Therefor, further examination of the components of the ink is needed. Ink is a mixture of substances and these substances have varying molecular polarities. The intrinsic properties of the components of the ink allows for the separation of ink through adsorption chromatography, where the ink is separated based on the attraction to a moving phase (liquid) and stationary phase (TLC plate). Using the Rf equation, the Rf value can be determine to numerically determine the similarity in the inks

"R" _"f" "=" "distance from the origin to the center of the spot" /"distance form the origin to the solvent front" (Eq. 1)

For the purpose of this experiment, I attempt to disprove what ink was used to write a letter by comparing the Rf values and colors through adsorption chromatrography. But before beginning this experiment, the class posed a series of question to guide our thinking; the questions were: What is the ID of the unknown ink? Can it conclusively be told what pen wrote the letter? What is the best solvent?

As stated before, ink is made of components with varying polarity and in order to separate these components we must determine the liquid and stationary phase that does this best. One of the three suspected inks is extracted with a 50% ethanol mixture and dotted onto 7 pieces of paper to be dipped in varying solutions. Each solution varies in polarity with the stationary phase held constant (paper). The solution with the greatest separation of the components within the ink will then be used on a TLC plate (polar) to test all four inks (3 suspected inks a...

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... point, the complete and full separation of the components, as those seen in the first part of the experiment, did not happen. This source of determinate error decreased the Rf values. Furthermore, upon placing my TLC plate into the solution I stumbled and threw the TLC plate in the jar. The solution splashed up on the TLC plate, rushing solution to move up and absorb on the TLC plate without capillary action. Because not all the solution that splashed up was not absorbed, it may have either dragged down some of the ink components or allowed for faster capillary action. This source of indeterminate error skewed the result of the Rf values, either increasing or decreasing the distance traveled of the ink. I don’t believe that this was a great source of error because the components of the unknown ink and the pen #3 still rose to similar values with similar separation.

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