Recrystallization and Melting-Point Measurement Identifying a Constituent of “Panacetin”

Topics: Solubility, Chemical substance, Temperature Pages: 3 (607 words) Published: October 29, 2012

To purify the component (unknown) of Pancetin from last experiment and then compare its melt point to the two other possible substances.

Panacetin should be made up of about 50 percent of the unknown component that we previously separated out of Panacetin for testing. We suspect that this unknown compound is either acetanilide or phenacetin. From the solubility of acetaminophen and phenacetin, we could know both of them are relatively soluble in boiling water but insoluble in cold water so that we took the recrystallization as the method to purifying the unknown component. After the unknown purified, then we could measure it melting point. This whole experiment is based on purifying and then finding the melting point of the unknown compound. The theory is that if a substance is pure, it will have a very specific melting point, within one or two degrees Celsius. This is in opposition to a mixed, or contaminated substance, which will have a broad melting range. Therefore, when we mix our unknown with samples of phenacetin and acetanilide, whichever mixture has a more accurate melting point will tell us what our unknown is. It is also important to make sure that the resulting melting points are close to what the proven melting points of the substances are.

Name of substance structure molecular weights solubilities c.w melting point solubilities b.w Acetanilide 135.2g/mol 0.54g/100mL 114℃ 5.0g/100mL

Phenacetin 179.2g/mol 0.076g/100mL 179.2℃ 1.22g/100mL

First, the unknown sample from experiment 2 was boiled with just enough water dissolve it completely. After all of...
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