Laboratory Experiments For General Organic and Biochemistry

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Experiment 1
Laboratory techniques: use of the laboratory
gas burner; basic glassworking

The Laboratory Gas Burner
Tirrill or Bunsen burners provide a ready source of heat in the chemistry laboratory. In
general, since chemical reactions proceed faster at elevated temperatures, the use of heat
enables the experimenter to accomplish many experiments more quickly than would be
possible at room temperature. The burner illustrated in Fig. 1.1 is typical of the burners
used in most general chemistry laboratories.
Figure 1.1
The Bunsen burner.

Violet outer cone
Pale-blue middle cone
Hottest part of the
flame (800°C)

Dark-blue inner cone


Air vents

Gas inlet

Gas control valve
Main gas valve

A burner is designed to allow gas and air to mix in a controlled manner. The gas often
used is “natural gas,” mostly the highly flammable and odorless hydrocarbon methane,
CH4. When ignited, the flame’s temperature can be adjusted by altering the various
proportions of gas and air. The gas flow can be controlled either at the main gas valve or at
the gas control valve at the base of the burner. Manipulation of the air vents at the bottom
of the barrel allows air to enter and mix with the gas. The hottest flame has a violet outer
cone, a pale-blue middle cone, and a dark-blue inner cone; the air vents, in this case, are
opened sufficiently to assure complete combustion of the gas. Lack of air produces a cooler,
luminous yellow flame. This flame lacks the inner cone and most likely is smoky, and often
deposits soot on objects it contacts. Too much air blows out the flame.

Harcourt, Inc.

Experiment 1


Basic Glassworking
In the chemistry laboratory, it is often necessary to modify apparatus made from glass or
to connect pieces of equipment with glass tubing. Following correct procedures for working
with glass, especially glass tubing, is important.
Glass is a super-cooled liquid. Unlike crystalline solids which have sharp melting
points, glass softens when heated, flows, and thus can be worked. Bending, molding, and
blowing are standard operations in glassworking.
Not all glass is the same; there are different grades and compositions. Most
laboratory glassware is made from borosilicate glass (containing silica and borax
compounds). Commercially, this type of glass is known as Pyrex (made by Corning Glass)
or Kimax (made by Kimble glass). This glass does not soften very much below 800ЊC and,
therefore, requires a very hot flame in order to work it. A Buns...
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