Quantitative Techniques in Volumetric Analysis
is a visual library of techniques used in making
volumetric measurements. This 40-minute VHS videotape is
designed as a resource for introducing students to
proper volumetric methods and procedures. The entire tape,
or relevant segments of the tape, can also be used to
review procedures used in subsequent experiments
that rely on the traditional art of quantitative analysis
laboratory practice. The techniques included are:
- Quantitative transfer of a solid with a weighing spoon
- Quantitative transfer of a solid with a finger
held weighing bottle
- Quantitative transfer of a solid with a paper
strap held bottle
- Quantitative transfer of a solid with a spatula
- Examples of common quantitative weighing errors
- Quantitative transfer of a solid from dish to
beaker to volumetric flask
- Quantitative transfer of a solid from dish to
volumetric flask
- Volumetric transfer pipet
- A complete acid-base titration
- Hand technique variations
The conventional view of contemporary
quantitative chemical measurement tends to focus on
instrumental systems, computers, and robotics. In this view, the
analyst is relegated to placing standards and samples on
a tray. A robotic arm delivers a sample to the analysis
center, while a computer controls the analysis conditions
and records the results. In spite of this, it is rare to find
an analysis process that does not rely on some aspect of
more traditional quantitative analysis techniques, such as
careful dilution to the mark of a volumetric flask.
Figure 1. Transfer of a liquid.
Figure 2. Transfer of a solid with a spatula.
Clearly, errors in a classical step will affect the quality of the
final analysis. Because of this, it is still important for
students to master the key elements of the traditional art of
quantitative chemical analysis laboratory practice.
Some aspects of chemical analysis, like careful
rinsing to insure quantitative transfer, are often an
automated part of an instrumental process that must be
understood by the analyst. This video material
carefully documents several options in the process of
quantitatively weighing and transferring a solid,
quantitatively transferring a liquid aliquot with a pipet, and the
process of quantitative volumetric titration.
There are many local variants in each of these
procedures. For example, some prefer to transfer solid with
a weighing spoon, some with a finger held bottle,
and some with a paper-strap held bottle. Students
should follow the local preference, but should be aware of
other acceptable options. Whatever the technique option
chosen, the procedure must be done reproducibly, if
analysis quality is to be optimized.
Acknowledgments
Quantitative Techniques in Volumetric Analysis
was created with support from Project SERAPHIM and
the NSF Directorate for Education and Human
Resources, grant MDR-9154099.
|
Citation
