Microscale Crystallization-Craig Tube

Topics: Solubility, Ethanol, Phase changes Pages: 2 (555 words) Published: October 11, 2011
Microscale Crystallization – Craig Tube
For this experiment, we had to find the percent recovery and melting point of pure sulfanilamide from impure sulfanilamide using the crystallization technique. To start, .1004 grams of impure sulfanilamide was put into a Craig tube with enough ethyl alcohol to barely pass the top of the sulfanilamide. The Craig tube was put into a stone block until boil, then check to see if the solid material had dissolve. With the addition of two more drops from a supply of 2.7 mL of ethyl alcohol the Craig tube was put back into the boiling stone and the process was repeated four more times until the solid was completely dissolved.

The Craig tube then transferred into a 100mL beaker to let cool down to room temperature. As the solution cooled down to room temperature crystals started to form. After reaching room temperature the Craig tube was then transferred into an ice bath until their no more crystallization. We then had to centrifuge the solution to separate the mother liquor and crystal. We then took the crystals out to try on a pre weigh watch glass (52.0994g) to dry. After drying the watch glass with crystal was weigh 52.1602g. It was found that the pure sulfanilamide recovery was .0608 with a percent recovery of .3944. Using the melting machine it was found that impure sulfanilamide had a melting point of 172 C and pure sulfanilamide had a melting point of 165.1 C. When comparing the boiling point of sulfanilamide to the actual boiling point (165-166 C) the experiment was right on. Comparing the boiling point of impure and pure sulfanilamide the impure had more substances in it so the boiling point was higher than the pure.

Table of Results
Impure Sulfanilamide.1004g
Ethly Alcohol2.7mL
Watch Glass52.0994g
Watch Glass + Sulfanilamide52.1602g
Pure Sulfanilamide.0608g
Percent Recover.3944g
Melting Point Started164.1C
Melting Point165.1C
Impure Sulfanilamide172C
Actual Melting Point165-166C...
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