The note by Joe Pizzo entitled "Video Spectrometer" (TPT 1996, 34, 458) is of interest as a demonstration for the introductory chemistry lecture. The innovative apparatus consists of a transparent diffraction grating placed over the lens of a video camera together with a laser pointer. This assembly is placed on a rotating platform. The platform is rotated until first-order spectral lines appear on the monitor. An accuracy of about one percent for the wavelength of the bright green line of mercury is reported.

An excellent introduction to the technology and terminology of vacuum systems is presented by Hansen (TPT 1997, 35, 8-14). Vacuum technology is important in instrumental techniques for spectrochemical analysis, and the article provides a valuable resource. Did you know that there are about 3.5 million molecules per liter even at the best possible vacuum attainable in the laboratory (10-13 Torr, about the pressure found in interstellar space)? This article provides a very useful discussion of the characteristics of a vacuum and the working of vacuum pumps. The concepts of mean free path, pumping speed and throughput, tubing conductance, outgassing and vapor pressure, and backstreaming are clearly explained. A discussion of the materials used in vacuum systems is included. The article also provides references to several resources for those educators with an interest in vacuum systems and projects.

Two recent articles on thermodynamics should be of interest for the gas laws portion of the curriculum. Peckham's note, "P-V Diagrams Have More To Offer" (TPT 1997, 35, 56], can be valuable to teachers of chemistry. The difference between isobaric, isothermal, adiabatic, and isochronic processes is clearly shown by use of a pressure vs. volume diagram. Examples of processes in which P, V, and T all change are explained along with compression of a gas, a subject often ignored by textbooks.

The note by Thomsen, "The Boiling Point of Water" (TPT 1997, 35, 98), shows that the Clausius-Clapeyron equation can be used effectively at introductory level. The boiling point of water is calculated for the reduced pressure at Denver and for a vacuum system at 20 °C. The first requires only algebra, while the second example uses calculus accessible to the first-year college or high school AP chemistry student.

"A High School Dye Laser Project", by Nicholas Guilbert (TPT 1997, 35, 72-77), is an exciting example of what can be done at the secondary school level. Basic concepts of the organic dye laser are introduced and construction details are included with a schematic diagram for the electronics and a complete parts list. The pedagogical advantages of such a project are discussed. No applications are included, as this was not the intention of the note; but perhaps these might be more appropriately developed by chemistry teachers.