Different steps for estimation the bod through titrimetric method
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There are two stages of decomposition in the BOD test: a .... chemical solutions used in the procedure for determination of 5-day biochemical oxygen ...
A TITRIMETRIC METHOD FOR THE QUANTITATIVE
ESTIMATION OF LEAD IN BIOLOGICAL MATERIALS
BY M. K. HORWITT* AND GEORGE R. COWGILL
(From the Laboratory of Physiological Chemistry, Yale University School of
Medicine, New Haven)
(Received for publication, March 31, 1937)
The announcement by Fischer in 1929 (1) of the remarkable
affinity of dithizone (diphenylthiocarbazone) solutions for lead
has stimulated many laboratories to search for practical micromethods that could be applied to the determination of lead in
biological materials. The theory and the application of such
methods have been adequately described by Wilkins, Willoughby,
Kraemer, and Smith (2), Ross and Lucas (3), and more recently
by Clifford and Wichmann (4) and will not be treated further
here.
The authors have had the opportunity to apply the various
dithizone methods to a large variety of materials. Most of the
published techniques have been critically investigated and this
paper will present what is in our opinion the most satisfactory
extraction procedure together with a new titration that eliminates
the necessity of investing in expensive photometric equipment.
Interference by Bismuth and Tin-The red color produced by the
reaction between solutions of dithizone in chloroform and those
of a heavy metal in alkaline cyanide solution is not entirely specific
for lead (5). Bismuth and stannous tin react with dithizone in a
similar fashion and must be eliminated at some point in the
analytical procedure. Bismuth may be present in biological specimens as a result of previous medication and stannous tin is not
an uncommon constituent of the normal diet.
Fischer and Leopoldi (6), Winter et al. (7), and Tompsett and
ilnderson (8) have made use of the fact that bismuth may be
separated from lead by extracting the dithizone mixture with
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