History: On the Human Side

Before 1920, the determination of the molecular composition and the molecular structure (geometry) of substances was achieved largely through conventional chemical analysis. It is much more difficult to determine the molecular architecture than the molecular composition in this way. The determination of structural characteristics was accomplished by interpreting the reactions of a substance and chemically identifying the resulting fragments. This type of analysis not only requires a relatively large amount of sample, but also results in the destruction of that sample.

Since 1930, much progress has been made in developing instruments that enable chemists to determine composition, molecular mass, and the geometry of molecules. Most instrumental analyses require only small samples (0.1 g or less) and are nondestructive (except for mass spectrometry). This means that the sample may be analyzed several times, using different instruments. Thus, several different characteristics of the sample may be determined. Combining the data from the different sources then will provide a composite picture of the molecule.

Other historical data is given in the Pictures in the Mind section.

A Brief Alphabetical List of the History Behind Instrumentation

Aston, F. W. (1877-1945). Developed the mass spectrograph about 1919. Awarded the Nobel Prize in 1922. He showed that neon actually consisted of three isotopes.

Beckman, A. O. (1900- ). A pioneer in the field of instrumentation. Founded the Beckman Instrument Co. This company produced the first relatively inexpensive pH meters and the first infrared spectrophotometers.

Bragg, W. H. (1862-1942) and Bragg, W. L. (1890-1971). A father-son team; pioneered work in X-ray diffraction analysis. They jointly developed what is known as Bragg's Law, relating the wavelength of radiant energy with the spacing in a diffraction grating or crystal and the diffraction angle. They jointly were given the Nobel Prize in 1915.

Bunsen, R. (1811-1899) and Kirchhoff, G. (1824-1887). Developed the emission spectroscope.

Crookes, W., Sir. (1832-1919). Developed the Crookes tube, the forerunner of the cathode ray tube that plays an important role in many instruments.

Davisson, C. J. (1881-1958) and Germer, L. H. (1896- ). Discovered that electrons would be diffracted by a crystal the same as X-rays. G. P. Thomson (1892-1975), the son of J. J. Thomson, and A. Reid also showed that electrons were diffracted. Davisson and Thomson shared the Nobel Prize in 1937 for this work. The recognition that electrons also had wave-like properties ultimately led to the electron microscope and similar instruments.

Moseley, H. G. J. (1889-1915). Used X-rays to determine the relationship between the characteristic K lines in an element's X-ray spectrum and the positive nuclear charge of element.

Roentgen, W. (1845-1923). Serendipitously discovered X-rays in 1895 and received the first Nobel Prize in physics for his discovery.

Thomson, J. J. (1856-1940). Discovered the electron in 1897 and positive "rays" in 1913. He suggested that it would be possible to use the rays to analyze chemicals as Aston and others were later able to show.

Humor: On the Fun Side

1. Word Search (see Appendix for master copy)

  1. Energy for nuclear magnetic resonance spectroscopy is supplied by this type of wave.

  2. Infrared radiation causes changes in the _____ lengths of molecules.

  3. Emission spectra consist of these transitions in molecules.

  4. Fraction of incident radiation not absorbed by a solution.

  5. Instrument that measures the wavelength and amount of absorption of specific wavelengths when electromagnetic radiation is passed through a substance.

  6. Method that separates mixtures based on solubility and absorptivity differences.

  7. Range of wavelengths and energies.

  8. Type of spectrum that results when molecules are fragmented by an ionizing beam of electrons.

  9. A = abc is an algebraic expression of the ____-Lambert Law.

  10. . Type of spectrum produced by molecular absorption of microwaves.

Answers: 1. RADIO 2. BOND 3. ELECTRON 4. TRANSMITTANCE 5. SPECTROPHOTOMETER 6. CHROMATOGRAPHY 7. SPECTRUM 8. MASS 9. BEER 10. ROTATIONAL

2. See cartoons at end of module.

Media

1. Software published by JCE: Software, a publication of the Journal of Chemical Education, Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue. Madison, Wl 53706-1396: (608) 262-5153 (voice) or (608) 262-0381 (FAX).


a. Bomb Calorimeter Simulation, by David J. Olney. Vol. III A, No. 2, for the Apple II computer.


b. The Computer-Based Laboratory , by Daniel Krause. Vol. I A, No. 2, for the Apple II computer.


c. EPR Spectrum Simulator, by Miguel A. Martinez-Jimeno, Ernesto Brunet and Carlos Sieiro, Vol. VI B, No. 1, for IBM PS/2, PC-compatible computers.


d. HPLC - An Instrument Simulator , by Robert C. Rittenhouse. Vol. I B, No. 2, for IBM PS/2, PC-compatible computers.


e. Mass Spec Simulation, by Bruce Armitage. Vol. IV B, No. 2, for IBM PS/ 2, PC-compatible computers.


f. NO 2 /N 2 O 4 Equilibrium Experiment, by Teresa Anderson Curtin, Darryl Wahlstrom and James A. McCormick. Vol. IV B, No. 1, for IBM PS/2, PC-compatible computers.


g. Organic Spectroscopy, by Richard Hiatt. Vol. II A, No. 2, for the Apple II computer.


h. Proton NMR Spectrum Simulator, by Kersey Black. Vol. II C, No. 1, for the Apple Macintosh.


i. Spec 20, by Ralph Gable and James McCormick. Vol. IV B, No. 1, for IBM PS/2, PC-compatible computers.

2. Software published by Falcon Software, Box 200, Wentworth, NH 03282; (603) 764-5788.


a. SpectraBook for Windows and SpectraDeck for Macintosh - An Annotated Collection of IR, NMR, CMR and Mass Spectra, by Paul F. Schatz. $95 for individual copies.


b. The Schatz Index for Macintosh , by Paul F. Schatz. The IR and NMR spectra, physical information, references, synonyms and safety data for 400 organic compounds. $200 for individual copies.


c.IR and NMR Simulators of Macintosh and MS-DOS. These simulators are low-cost and wasy to use; they are no-maintenance simulations of the real instruments. Data sets for 300 compounds are available separately. $95 for individual copies of NMR simulator, $75 for individual copies of IR simulator, $200 for IR data set, $250 for NMR data set.

3. Software published by Project SERAPHIM, Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue. Madison, Wl 53706-1396: (608) 263-2837 (voice) or (608) 262-0381 (FAX).


a. For the Apple II computer running on ProDOS: AR 1201.


b. For the Apple II computer: AP 1201; Laboratory modules LM 002, LM 003, LM 004, LM 005, LM 006, LM 012, LM 015, LM 016, LM 021 (for the Project SERAPHIM Blocktronic and Thermistor).


c. For IBM PCs and PC-compatibles: PC 4201; Laboratory modules LM 002, LM 003, LM 004, LM 005, LM 006, LM 012, LM 015, LM 016 (for the Project SERAPHIM Blocktronic and Thermistor).

4. Videodiscs published by JCE: Software, a publication of the Journal of Chemical Education, Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706-1396: (608) 262-5153 (voice) or (608) 262-0381 (FAX).

"Mercury Determination Using A Spectrophotometer - Accuracy and Precision," and "A Generic Spectroscopic Instrument," two chapters on The World of Chemistry: Selected Demonstrations and Animations : Disc I (double sided, 60 min.), Special Issue 3.

5. Films and videocassettes published by Ward's Natural Science Establishment, Inc., 5100 West Henrietta Road, P.O. Box 92912, Rochester, NY 14692-9012; (716) 359-2502; (800) 962-2660; (716) 334-6174 (FAX).


a. Crystals and Their Structures (CHEM Study 16-mm film and/or VHS cassette)

The film covers the properties of crystals, their well defined diffraction patterns in interactions with X-rays, leading to their description as regular, repeating arrangements of atoms. It includes a ripple tank activity showing the principles and measurements by which crystal structures are determined. Good for above average and honor students. It is especially recommended if it is desired to take the student beyond the material on X-ray diffraction presented in this module.


b. Molecular Spectroscopy (CHEM Study 16-mm film and/or VHS cassette)

The film presents laboratory activities, molecular models, and animation that shows the infrared light absorption process and its relation to molecular properties. It stresses the concept of natural molecular vibrational frequencies, and how the infrared spectrum is used to identify molecules and determine their structures. Good for the above average and the honor student.

To receive information about subscriptions to JCE: Software or a summary of the many software and videodisc issues available, contact: Journal of Chemical Education: Software, Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706-1396; (608) 262- 5153; (608) 262-0381 (FAX).

To become a member of Project SERAPHIM or to obtain a copy of the Catalog with over 600 programs of instructional software for chemistry teaching, contact: Project SERAPHIM, Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706-1396; (608) 263-2837; (608) 262-0381 (FAX).

Equipment and Instrumentation

Several student spectrophotometers are available. Probably the one used most is the Spectronic 20 " manufactured by the Milton Roy Company. It is available with either an analog meter display or with a digital readout. The Spectronic 20 " is available from most laboratory equipment suppliers.

Several spectrophotometers designed to use a computer are also available. The Blocktronic uses inexpensive materials and software for an Apple II computer. The plans and software may be obtained from Project SERAPHIM (see address in Media).

A GowMac gas chromatograph may be obtained from several suppliers as well as electrophoresis and gel electrophoresis equipment and power supplies. CEPUP (Chemical Education for Public Understanding Project) materials are available from Addison-Wesley Publishing Company, EMD Fisher Scientific Company, Laboratory Aids, Inc., Science Kit and Boreal Laboratories, and Sargent-Welch Scientific Company (see catalogs published by these companies).

The Optical Transform Kit, available from ICE-Institute for Chemical Education, Department of Chemistry, University of Wisconsin-Madison, 1101 University Ave-nue, Madison WI 53706-1396; (608) 262-3303 (voice) or (608) 262-0381 (FAX).


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