Amanda Zabotsky
Section3
October 31, 2007
Dr. Zirpoli
Crystallization of sulfanilamide.
Introduction
The purpose of this experiment was to crystallize a sample of sulfanilamide and
create a more pure sample from a tainted sample and retrieve a relative melting point by
the use of a melting point apparatus and compare the samples and determine if they were
near the given melting points as found on www.chemfinder.com.
Reagent Table
Items included in this table were pulled from the chemfinder.com website.
Molec.
Molec.
Melting
formula
weight
pt
Sulfanilamide C6H8N2O2S 172.201
164.5—
Boiling pt
density
--
1.08
166.5 C
Ethyl alcohol
C2H6O
46.068
-114.1 C
78.3 C
1.6
acetanilide
C8H9NO
135.16
114.3 C
304.0 C
--
Procedure:
9.5mL of ethyl alcohol was added to 1.50 g of impure sulfanilamide and was then
placed in a 25 mL Erlenmeyer flask and brought to a boil on a hotplate and was dissolved
within a few minutes. Once this was achieved it was placed in an ice bath with an air
current blown over the lip of the Erlenmeyer flask. Once the crystals formed this was
transferred to a vacuum filter using a Buchner funnel where the remaining liquid was
pulled to the flask below and the crystals remained above.
The crystals were then set aside to dry and placed in a vial until the following lab
period where they were pulverized and placed in a melting point tube then placed in a
melting point apparatus with a sample of impure sulfanilamide and the melting points
were compared to those found on the chemfinder.com website.
Results:
Upon the crystallization of the Sulfanilamide the melting point of the pure sample
was determined to have the melting point of 164- 166 C and the impure was found to
melt at 151-152 C. the melting point of the purified sulfanilamide was in the range that
was provided by chemfinder.com.
The amount of recovery was found to be 67.087%
Because of the equation of: (recovered pure/ initial impure) x 100.
Or (1.011 / 1.507) x 100 = 67.087.
This is found to be an adequate amount because crystallization is a wasteful
experiment however still efficient. Some places where errors may have occurred is in the
transferring between the 25 ml Erlenmeyer flask and the Buchner funnel some crystals
may have been left over, some may have been lost from over—evaporation of the ethyl
alcohol or to human error with the reading of the scale.
Discussion:
Although crystallization is wasteful it was a better option to retrieve the melting
point of the sulfanilamide because it was combined with ethyl alcohol at two vastly
different temperatures where if the use of a distillation, be it fractional, steam, or simple;
the treatment at two different temperatures would not have had the same effects and had
the result of having the suggested boiling point that was found on the chemfinder.com
website.
References:
Pavia, D. L., Lampman, G. M., Kriz, G. S., & Engle, R. G. (2005). Introduiction to
organic laboratory techniques a small scale approach. canada:Thomas Learning , INC.
“Chemfinder.com” Chemfinder.com database and internet searching. 2004. Oct. 16,
2007 Http:// www.chemfinder.com