Burner and Glassware Use and Safety List one type of material that should never

Question

Burner and Glassware Use and Safety List one type of material that should never be heated with a bunsen burner. Where should these substances be heated? Describe the two major control features of a bunsen burmer. Describe several safety checks that a student should perform before using a bunsen burner. Should a bunsen burner flame appear yellow? What need adjustment need to be to your bunsen burner if the gas flame is yellow? Describe the appearance of a good bunsen burner flame and tell where the hottest part of the flame would be. What conditions would require that you turn the gas off immediately? What should you check glassware for before heating it? What safety proceedure should be followed when heating narrow necked containers? Describe the best technique to heat a material in a test tube. Explain why it is not a good idea to heat a container that has been tightly sealed if the container has a liquid in it. A commonly heard sentence in the lab is "But it didn't look hot when I picked it up with my hands." Explain how glassware, iron rings and other materials that have been heated on a burner should be handled.

Explanation / Answer

1. Generally thick-walled glassware and ceramics are designed to be heated under open flame such as the bunsen burner. Other thin-walled glassware like fusion tubes and even test tubes are not designed for prolonged heating under an open flame. Mainly, laboratory equipments made of plastic, wood or rubber should never be heated using a bunsen burner. Also it is not advisable to heat nickel spatulas in a bunsen burner as they tend to lose their inertness at such temperatures and form oxides on the surface which might react with some compounds.

2. In general equipments made of thin-walled glass are heated in heating mantles or oil bath or water bath by careful and continous control of the temperature as exposing these equipments to open flame will either result in their breakage or cracking.

3. The control features of a bunsen burner are the flame adjustment ring just above the base, used for controlling the oxygen supply to the burner and the second control which is at the gas supply at the start of the tube to the burner. This is used to control the rate of fuel supply to the burner and comes handy to prevent mishaps in case of burner malfunction.

4. Before using a bunsen burner, first a student should open the gas valve sparingly and check for any ethyl mercaptan smell or hissing sounds from the tubeline or elsewhere indicating leakage of gas, all before lighting the burner. Then one should look for charring or any such blockage in the burner especially in the burner's rod-like part as this will result in excessive pressure build-up in the line which can cause an explosion. Moreover one should check if the control features of the burner are functional.

5. A bunsen burner's flame is usually bright blue. This bluish flame however arises only when the hydrocarbons in the gas (which is the fuel for the burner) undergoes complete combustion. For complete combustion of gas, excess oxygen is required. When a burner flame is deprived of required oxygen, it tends to appear yellow and results in incomplete combustion which is observed as soot deposited on the mouth of the burner. Therefore to avoid a yellow flame, the burner ring should be adjusted to ensure proper supply of oxygen.

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