On temperature of boiling of liquid it is possible to judge its purity. Content of impurity or the dissolved substances usually lowers a boiling point. In laboratory this parameter can be determined by practical consideration previously to estimate high quality of the necessary liquid.
It is required to you
- - round-bottomed flask with a wide throat;
- - rubber stopper with two openings;
- - the bent glass tube for removal of steam;
- - thermometer;
- - heating device.
1. In a round-bottomed flask with a capacity not less than 50 ml pour the studied liquid for which it is necessary to determine boiling temperature. The amount of liquid in a flask should not exceed 1/4 its volumes.
2. Cork a flask and fix on a support for a neck. At the same time do not clamp too strongly a pad that the flask did not crack. In a stopper insert a glass tube for removal of vapors that the device was not completely tight into one opening.
3. Insert the thermometer into the second opening of a stopper. The mercury ball of the thermometer has to be over the liquid if it clean, but not to concern it. If you need to determine boiling temperature for solution, the end of the thermometer lower 1-2 cm in liquid, depending on amount of juicy solution. You watch that the thermometer did not concern walls and a bottom of a flask.
4. Prepare the heating device. If the studied liquid presumably has high temperature of boiling (more than 90 degrees), it is necessary to heat on a sandy bath. For this purpose lower a flask in the container with sand that liquid was lower than the level of sand. Consider that you need to see when it begins to boil. The sandy bath can be heated on a tile.
5. If you heat to 90 degrees, use for this purpose an electric tile. A pad with a flask on a support arrange so that the flask was slightly above a tile (1-1.5 cm), but did not concern it as when heating it can burst.
6. As soon as you assembled the device, begin to heat. Quicker to heat liquid on a sandy bath, you can wrap up a flask in fiber glass fabric. It will keep heat. Periodically check whether liquid boils. As soon as it began to boil, write down indications of the thermometer.
7. Most precisely to determine boiling temperature, make one more or several experiments. Then calculate average value of temperature. For this purpose put all indications of the thermometer at which liquid begins to boil, and divide into the number of the made experiments.