Melting Point Lab

Melting Point Determination and Thermometer Calibration Lab

Background: The melting point of a substance, a solid in this case, signifies the temperature at which the first crystal starts to melt until the temperature at which the last crystal disappears is reached. That being said, melting points are expressed in ranges, am organic compound will have a sharp range depending on the purity of the compound. Impurity of an organic substance will register an abnormal melting point based on its expected propensity observed, this will cause the temperature range to widen. Using this hypothesis, mixed melting point technique could determine if the unknown compound added to the mixture causes a temperature depression, if not, the unknown is likely to be the same as your starting compound. Results:
Melting Point: Compound | Experimental (°C) | Lit value (°C) | Ice-water | 2°C | 0°C | Naphthalene | 81-83°C | 80-82°C | Acetanilide | 113-116°C | 113-115°C, 128-129°C | Acetylsalicylic acid | 136-140°C | 135-140°C | Salicylic acid | 159-162°C | 158-160°C | Succinic acid | 186-188°C | 185-189°C |

Compound Structure: Naphthalene | Acetanilide | Acetylsalicylic Acid | Salicylic acid | Succinic acid | Water |
Eutectic Point Determination: Melting Point Compound | Experimental | Lit value | Urea | 131-134°C | 132.7°C +/- 1 | Trans-cinnamic acid | 134-137°C | 135°C +/-1 |

Mixture Melting Points: Urea | Trans-cinnamic acid | Experimental °C | 4 | 1 | 115-125°C | 2 | 1 | 101-115°C | 1 | 1 | 72-115°C | 1 | 2 | 108-117°C | 1 | 4 | 106-115°C |

Unknown #2: Araya Melting Point (experimental) | Compound | Lit Value | 116-121°C | Benzoic Acid | 121.5-122°C |

Unknown #53: Chanel Melting Point (experimental) | Compound | Lit Value | 155-159°C | Salicylic acid | 158-160°C |

Discussion:

The melting points in part A of the lab had the experimental values for the compounds that were within +/-2°C of the lit values. This is