لخّصلي

Experimental Procedure: We will use the boiling-point method.The heating mantle is connected to a Variac (variable transformer); increasing the voltage increases the temperature.Switch on the Variac, at a setting of about 20-30 V Using the vacuum pump, decrease the system pressure until the liquid begins to boil, the liquid may superheat above its boiling temperature; tapping the flask with your finger may initiate the boiling.The pressure inside the apparatus is thus equal to Patm-Ah, where Ah, is the difference in the heights of the mercury columns in the two arms of the manometer.Attach the empty boiling flask to the bottom of the condenser, using the jack support to hold the heating mantle beneath it. Be careful to not raise the jack too far, which could break the apparatus.Close the stopcock to the vacuum pump and observe the manometer for several minutes.Turn on the cooling water supply to the condenser, from the refrigerated circulation-water bath.Connect the system to the vacuum pump and evacuate it to 10 torr or less.Attach the flask to the condenser.

Experimental Procedure: We will use the boiling-point method. Note that we are using an open-end manometer. The pressure inside the apparatus is thus equal to Patm-Ah, where Ah, is the difference in the heights of the mercury columns in the two arms of the manometer. Record the values of Patm and the laboratory temperature. Check Patm every hour in case it should change significantly. Before using any apparatus is partially evacuated, we should check that it does not leak. Attach the empty boiling flask to the bottom of the condenser, using the jack support to hold the heating mantle beneath it. Be careful to not raise the jack too far, which could break the apparatus. Connect the system to the vacuum pump and evacuate it to 10 torr or less. Close the stopcock to the vacuum pump and observe the manometer for several minutes. If there are no leaks, the mercury levels should be constant. Open the stopcock to the atmosphere and remove the boiling flask. Fill the boiling flask about one-third full with your assigned liquid. Add about 10 boiling chips. Attach the flask to the condenser. Turn on the cooling water supply to the condenser, from the refrigerated circulation-water bath. The flow indicator in the water line will spin, to show that water is circulating. The heating mantle is connected to a Variac (variable transformer); increasing the voltage increases the temperature. Switch on the Variac, at a setting of about 20-30 V Using the vacuum pump, decrease the system pressure until the liquid begins to boil, the liquid may superheat above its boiling temperature; tapping the flask with your finger may initiate the boiling. Keep the stopcock in the line to the manometer closed, except when you want to measure the pressure. This is to prevent liquid vapor from entering the manometer and condensing in it.