Column Chromatography Chemistry 227 Laboratory Column Chromatography Separating a mixture of food coloring.

You will be provided with a two-foot length of glass tubing. From this you can prepare TWO chromatographic columns.

You need a good hot flame You need a good hot flame!! Rotate evenly with BOTH hands, while pushing slightly toward the center to “gather wall thickness”. If you hold with one hand and rotate with the other, you will tie the glass into an UGLY KNOT as it softens.

Remove from the flame and pull steadily in opposite directions as the center constricts. Hold the glass for a few seconds and allow the glass to cool and re-set.

When the glass has re-set, burn it in two at the constriction. As the glass separates, allow the “beads” to form at the ends, closing off the columns. Now you have made TWO columns.

Don’t put the hot glass down on a cold bench top. Don’t pick it up again until you are SURE it has cooled.

Select a suitable-sized cork to support the column; or use some other method as suggested in Zubrick’s earlier edition . . . The 7 mm O.D. glass tubing should fit through the hole in your thermometer holder, -- but DON’T FORCE IT!

With a piece of tubing, fit a small funnel to the top of the column. This will make it easier to pack the column.

Clamp the column vertically on a ring stand. Place a small receiver beneath the column.

DO NOT pack it tightly, or the column will drain much too slowly. With the small diameter glass rod, push a small pellet of cotton into the narrow end of the column. DO NOT pack it tightly, or the column will drain much too slowly.

Next, add a bit of clean sand. No need to overdo it ! Next, obtain a few grams of chromato- graphic alumina and prepare to pack the column. Next, add a bit of clean sand. No need to overdo it !

Now, add the alumina to within about 10 cm (3-4 inches) from the top! Add in small portions, tapping the column so the vibration will cause the alumina to pack tightly and evenly.

Now, add a bit more sand to the top of the alumina. Remove the funnel, and prepare the 70 percent methanol eluent.

Liquids do not mix well in small diameter vessels; (pousse café )? So, -- pour the mixture into a beaker and MIX IT THOROUGHLY.

Some of the mixture may cling to the glass walls of the column. When all is ready, add several drops of the dye mixture to the top of the column. Some of the mixture may cling to the glass walls of the column.

FIRST, break off the tip at the bottom of the column. Let the mixture be absorbed into the sand; THEN, rinse the sides of the column with a few drops of eluent. FIRST, break off the tip at the bottom of the column.

As the column drains, continue to add eluent to the top of the column. When the leading color is about half way down, fill the column. Label the column with your name, and leave it to drain until the next lab. As the column drains, continue to add eluent to the top of the column.

Place your column into the beaker provided for your section Place your column into the beaker provided for your section. They will be drained and dry by your next lab period.

Thin – Layer Chromatography Chemistry 227 Laboratory Thin – Layer Chromatography Determining the components in “proprietary aspirins”

Place 5 – 6 mLs of TLC solvent into a 100 – 150 mL beaker. Cover the beaker with a watch glass or a piece of Parafilm.

Heat a melting point capillary over a very small flame. Rotate the capillary evenly with BOTH hands until the center softens and begins to sag. BUT DON’T PULL YET!!

Remove the capillary from the flame and PULL . . . Hold it for a few seconds until the glass cools and re-sets.

Snap the capillary in two at the center. Now you have TWO “spotters” . . .

Assume an origin line on the TLC plate is JUST ABOVE the solvent level in the beaker; or make a reference “notch” (Zubrick). Place four evenly spaced dots on the origin line, and identify the proposed spots at the top of the plate.

Place samples of the unknown and 3 references into spotting plates Dip a “spotter” into a sample; a bit of liquid is drawn into the capillary.

Touch the “spotter” to the plate; a bit of sample will wet the dot. Blow on the spot to hasten drying; and re-spot if necessary. Repeat with other “spotters” at their respective spots.

Place the plate into the developing beaker. It may take 10 – 15 minutes for the solvent front to approach the top. Mark the solvent front with a pencil, and allow the plate to air-dry.

When it is dry, examine the plate while it is in the UV light box.

Compare the height to which the spots have risen . . . Identify the components by comparing their positions with the references.

Sketch the results on your lab report. Identify the components you found.

Turn in your Lab Reports from the Extraction Experiment along with the benzoic acid AND the p-dichlorobenzene. You may be asked to KEEP the aniline to be used in a later experiment.