Titration Techniques begins by developing the concept of titration through a very simple experiment. A liquid is poured from a graduated cylinder into a beaker and a second liquid is added until a color change occurs. Approximate volumes are read from the cylinders. An animation of this acid-base titration follows, illustrating molecular behavior and stoichiometry underlying this titration. Next is shown a segment of a permanganate titration, this time using a buret, accompanied by an appropriate animation. Once the concept has been established, a relatively complete acid-base titration is shown that focuses on cleanliness, accuracy, and safety. These and the following lessons are accompanied by a voice-over explanation.

Figure 1. A meniscus is properly viewed at eye level.

Titration Techniques demonstrates all important procedures involved in titration. As much as possible the techniques are shown independent of a specific titration chemistry. A series of video clips illustrates: various techniques for manipulating buret, stopcock, and flask; how to use a magnetic stirrer; how a stopcock works; and several methods for measuring liquid volumes, including a section on proper recording of significant figures when measuring liquids with common glassware. The disc also includes clips on why one should wait before reading a meniscus, how to distinguish dirty from clean burets, and why one should use clean burets.

Figure 2. Closeup of a meniscus for student reading practice.

Significant attention is paid to the proper technique for reading a meniscus. Video shows meniscus-viewing techniques for colorless and dark liquids and the consequences of not reading a meniscus at eye level. Lessons are provided on approaching the end point, focusing on end point colors produced via different commonly used indicators. The concept of a titration curve is illustrated by means of a pH meter.

Carefully recorded images of the entire range of meniscus values in a buret, pipet, and graduated cylinder are included so that you can show your students, in lecture or pre-lab discussion, any meniscus and discuss how to read the buret properly. These buret meniscus values are very carefully recorded at the rate of one video frame per hundredth of a milliliter, so that an image showing any given meniscus value can be obtained. These images can be easily incorporated into a computer-based multimedia environment for testing or meniscus-reading exercises. Two of the authors have used this technique and found the exercise to be very well received by their students.

Video on side two shows nearly 100 "bloopers", demonstrating both the right way and wrong ways to do tasks associated with titration. This material can be used in a variety of situations: to show students the correct way to do something; to test students by asking them "What is this person doing wrong?"; or to develop multimedia, computer-based lessons.

The contents of Titration Techniques are listed below:

Side 1

• Titration: what it is. A simple titration; Acid-base titration animation; A brief redox titration; Redox titration animation; A complete acid-base titration.

• Titration techniques. Hand technique variations; Stopcock; Using a buret to measure liquid volumes; Wait before reading meniscus; Dirty and clean burets; Read meniscus at eye level (see Fig. 1); Meniscus viewing techniques--light colored liquids; Meniscus viewing techniques--dark liquids; Using a magnetic stirrer; Rough titration; Significant figures; Approaching the end point; End point colors; Titration with a pH meter; Titration curves; Colors of indicators.

• Meniscus values. Buret meniscus values; Pipet meniscus values; Graduated cylinder meniscus values.

Side 2

• "Bloopers". Introducing the people; Titration animation; Inspecting the buret; Rinsing the buret with water; Preparing a solid sample; Obtaining a liquid sample; Delivering a liquid sample with a Mohr pipet; Pipetting a liquid sample with a Mohr pipet; Rinsing the Mohr pipet with sample; Using the Mohr pipet to transfer sample; Delivering a liquid sample with a volumetric pipet; Pipetting a liquid sample with a volumetric pipet; Rinsing the volumetric pipet with sample; Using the volumetric pipet to transfer sample; Obtaining the titrant; Rinsing the buret with titrant; Filling the buret with titrant; Adding the indicator; The initial reading; Beginning the titration; Delivering titrant; The final reading.

Figure 3. Near the end point a single drop of titrant can cause a lasting color change.