For experiment 2, a monometer will be used to determine the pressure in the system. The reading on the monometer is the amount the pressure has been reduced below atmospheric pressure. If the atmospheric pressure is 710 mm in mercury and the monometer reads 650 mm in mercury, then the pressure in the system is 60 mm in mercury. To zero the monometer, make sure the vacuum is off and the system is open to the atmosphere. Turn on the monometer and push the hold button for 2 to 3 seconds. To prevent the transfer of grease and moisture to the sample bottle, you will need to use finger-cots or a lint-free tissue. Attach the sample bottle to the system being careful to handle it by the stopcock. Make sure that the path back to the vacuum is open and that any stopcocks that open to the atmosphere are closed. Turn on the vacuum to evacuate all of the gases from the system. When the monometer reading stops increasing, close the stopcock that leads to the vacuum. Check the monometer. If the reading is steady, there are no leaks. If the number is decreasing, there is a leak. To fix the leak, tighten all nuts on the stopcock and make sure the bottle is firmly attached. Evacuate the system again. Hold the monometer reading and immediately close the two stopcocks that lead to the sample bottle. Write down the pressure reading. Remove the closed sample bottle from the system and determine its mass on the balance. Remove the bottle from the balance. To fill the bottle with air, open the stopcock. Determine the new mass on the balance. To fill the system with argon or natural gas, connect the fill tube to the gas tap. Evacuate the system. Fill the system with gas to approximately 50 mm of mercury below atmospheric pressure. Make the process of evacuating and filling with a gas at total of three times to remove all traces of previous gases.