Environmental Sciences, asked by pinkysainiar9167, 1 year ago

Different steps for estimation the bod through titrimetric method

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Answered by arya6907
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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 ...


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Answered by kusumasree789
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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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