REPORT FOR ANALYSTS
BIDDLEInstrumentNews
clature Committee of the Division of Analytical Chemistry of the AMBEICAN CHEMICAL SOCIETY says in its latest
report (1):
A P I E Z O N OIL DISTILLATES for H I G H VACUUM W O R K T h e s e Apiezon products h a v e t h e recognition of leading scientists w h o accord t h e m t o p preference for high v a c u u m work. Because of t h e exceedingly low vapor pressure of all these oil distillates, a t usual room temperatures, t h e y are i n great demand for all sorts of high v a c u u m work. Their vapor pressures are as low as 10- 6 m m . H g , a n d e v e n unmeasurable at room temperature. A s t h e exclusive distributor i n t h e U n i t e d S t a t e s , w e offer immediate delivery from stock o n t h e complete range of these oils a n d compounds. For applications, working characteristics and list prices, write for Bulletin 43-AC.
LEYBOLD MERCURY EJECTORS and DIFFUSION PUMPS The Model Hg 3 mercury diffusion pump reaches its full pumping speed at pressures below 10- 2 mm. H g and remains constant down to 10- 5 mm. Hg. The mercury ejectors models Hg 12 and Hg 45 reach maximum pumping speed a t pressures between 10-! and 10- 2 mm. H g . Specially designed jets permit constant pumping speed at pressures between 10- 3 and 10- 5 mm. Hg. The pumps begin t o operate at considerably higher pressures. The ultimate vacuum is better than 10- 6 mm. Hg. We welcome your inquiries on this equipment and the accessories for it. Write for Bulletin 44-AC.
Titration is a determination of the reactive capacity, usually of a solution. Titrimetric signifies measurement by titration. This point of view sanctions the picturesque term, coulometric titration. Other definitely chemical methods are those measured by reaction kinetics and by oxidation potential. On the other hand, observations of color and odor are dependent upon physiological reactions of the observer and are therefore biological operations. In classifying so-called electrochemical methods of analysis, distinction is made between those that merely involve electrical indication of titration end points and complete analytical methods such as polarography and electrodeposition. Undoubtedly, any classification will have aspects that invite revision by the reader, either for special purposes or on a fundamental basis. The one presented herewith is the product of many revisions by the author and will probably soon be changed again.
Summary A classification system for analytical methods gives boundaries to the field and brings order to the list of methods. A system is useful to teachers, students, and librarians. It also points out areas where the opportunity exists for devising new methods. A classification system makes possible cross referencing and developing an indexing system such as the decimal method. Such a classification system permits a rapid and accurate comparison of analytical methods on the basis of general theory; characteristics such as rapidity, accuracy, sensitivity, complexity (mathematical or operational), cost (initial and operational); and applicability.
Literature Cited (1) Hughes, H. K., et al., ANAL. CHEM. 24,
J A M E S G . BIDDLE C O .
1349-54 (1952). (2) Patterson, G. D., Jr., Mellon, M. G., J. Chem. Educ. 26, 468-71 (1949). (3) Serfass, E. J., Steinhardt, R. G., Jr., Strong, F. C.,
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22, 966-9 (1950).
See classification system, page 27 A
