REPORT
These are the world's most widely used spectrophotometers
Paint chips, which are examined by chemical, instrumental, and micro scopic techniques, yield much infor mation to investigators.
More than 15,000 Coleman diffraction Grating S p e c t r o p h o t o m e t e r s are used in laboratories throughout the world. They have gained this wide acceptance because they deliver precise data more quickly and easily than any other spectro photometer. They have proved themselves to be rugged and reliable in laboratory service. The Coleman Universal Spectrophotometer is ideal for the laboratory with a variety of ana lytical problems and a heavy work-load. Fast, precise, versatile in spectrophotometry—fluorimetry—nephelometry. T h e Coleman Junior S p e c t r o p h o t o m e t e r —the most practical and effective of all analytical tools for routine spectrophotometric analysis. 15 years of service and thousands of published pro cedures illustrate its reliability and recognition by the highest authorities in analytical chemistry. New literature available. Junior Spectrophotometer Bulletin B-240A Universal Spectrophotometer Bulletin B-241
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Spectrophotometers COLEMAN 28 A
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INSTRUMENTS
I N C . , DEPT. A ,
MAYWOOD,
Circle Nos. 133-1, 133-2 on Readers' Service Card ANALYTICAL CHEMISTRY
ILLINOIS
paint examinations, three limiting factors normally present themselves almost automatically—the paint evidence is dry, small, and con taminated. This particular type of examination leans heavily on in strumental analysis. Under the microscope many important factors of identification and comparison can be discerned. These include layer structure, colors, texture, and surface peculiarities such as orange peel, wrinkling, cracking, and blis tering. Cleaning of the specimens, layer separation, and preparations essential for instrumental analysis are carried out under the micro scope. Frequently, infrared spec trophotometric analysis reveals the type of paint—i.e., lacquer, alkyd, acrylic, or styrene. Organic color ing agents, if present, can be re moved in solvents and studied on the recording spectrophotometer (4000 to 10,000 Α.). Metallic pig ments and the extender in paints in many instances can be identified. Rutile and anatase forms of tita nium dioxide and lead chromâtes are a few of the complex pigments in small samples which are adroitly fingerprinted by x-ray diffraction which might otherwise only be categorized by other examinations. The electron microscope with its electron diffraction adaptation is called into play to perform similar identifications when only micro samples are available. The emission spectrograph reveals not only the basic metallic constituents of paints but also traces which normally indicate the
