05.05 Mixtures and Solutions

Choice 2: Ink Chromatography

Before You Begin: You may either copy and paste this document into a word processing program of your choice or print this page.

Safety Warnings:

• Rubbing alcohol (or isopropyl alcohol) is flammable, so be sure to keep it away from high heat or heat sources.
• Keep pigments and solutions away from your eyes, wash your hands carefully after coming in contact with any solutions or pigments, and clean up spills with soap and water immediately after they occur.
• This lab can be a little messy, so be sure to work at a kitchen counter or in another area that can be easily wiped down if anything spills. It is also a good idea to lay down newspaper on the countertop before setting up the lab to help keep the counter surfaces clean.

Materials:

• Four different markers (including one black permanent marker)
• Rubbing alcohol or isopropyl alcohol
• Coffee filters (2)
• Tall glasses or plastic cups (2)
• Pencil
• Ruler
• Tape
• Table salt
• Water
• Measuring cups/spoons
• Clean pitcher or 2-liter bottle

Procedure:

1. Coffee filters usually are round, but it's easier to compare your results if the paper is rectangle. So, your first task is to cut the coffee filter into a rectangle measuring three cm by nine cm. You will need two of these strips to complete the lab.
   
2. Using a pencil (do not use a pen), draw a line one cm (1/2 inch) from the edge of one end of one strip of paper.
   

   
   

3. Make four pencil dots (one for each marker you will be examining) along this line, about 0.5 cm (1/4 inch) apart. Underneath each dot, label the marker that will be tested. You won't have space to write the whole color or brand name, so try abbreviations.
   
   
4. Use the markers to draw a different colored dot on each of the appropriate pencil marks on the paper strip. Allow the ink to dry, and then go back and add more color to each dot.
   
   
   Before you complete the rest of the lab, make a prediction of the pigment components you expect to see from each marker’s ink.
   
   
5. Prepare the salt solution by mixing 1/8 teaspoon of salt and three cups of water in a clean pitcher or 2-liter bottle. Stir or shake the solution until it is dissolved. This will produce a 1% salt solution.
   
   
6. Pour the salt solution into a clean tall glass so that the liquid level is 1/4 inch (0.5 cm).
   
   
7. Tape the strip to a pencil and rest the pencil on top of the jar so that the strip hangs into the jar. The goal is to have the end of the chromatography strip just touching the surface of the solvent solution, with the colored dots above the surface of the liquid. Make sure that the colored spots do not come in direct contact with the liquid in the bottom of the glass.
   

   
   

8. Capillary action will draw the salt solution up the paper. As it passes through the dots, it will begin to separate the dyes. When the salt water is 1/4 inch (0.5 cm) from the top edge of the paper, remove it from the glass and place it on a clean, flat surface to dry.
   
   
9. Repeat steps two through nine (using the second strip of paper and a clean glass) to test the same four colors using the alcohol instead of the saltwater solution at the bottom of the glass.