Common Operations and Wet Chemical Methods in Environmental Laboratories - Fundamentals of Environmental Sampling and Analysis - page 155

from the sample by the addition of H 2 SO 4 , heated to 70 C and the resulting
H 2 S is carried by a stream of N 2 into zinc acetate gas scrubbing bottles, where
it is precipitated as ZnS. This pretreatment will measure all the acid-soluble
sulfide species. If this step is replaced by the addition of HCl, tin(II) chloride,
and 100 C, ''acid-insoluble'' sulfide can be released and determined semi-
quantitatively. Tin (II) is added to prevent oxidation of sulfide to sulfur by the
metal ions such as Cu 2þ .
REFERENCES
American Chemical Society (2003), Safety in Academic Chemistry Laboratories Vol. 1, Accident
Prevention for College and University students, American Chemical Society Committee on Chemical
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APHA (1998), Standard Methods for the Examination of Water and Wastewater, 20th Edition Washington,
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B ERGER W, M C C ARTY H, S MITH R-K (1996), Environmental Laboratory Data Evaluation, Genium
Publishing Corporation Amsterdam, NY.
* C SUROS M (1997), Environmental Sampling and Analysis: Lab Manual, Lewis Publishers, Boca Raton,
FL.
HACH Company (1992), HACH Water Analysis Handbook, 2nd Edition, Loveland, CO (Procedures
available: http://www.hach.com).
National Research Council (1995), Prudent Practices in the Laboratory: Handling and Disposal of
Chemicals, National Academies Press, Washington, DC.
M ABIC S, R EGNAULT C, K ROL J. 2005, The misunderstood laboratory solvent: Reagent water for HPLC.
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Occupational Safety and Health Administration (1990), Laboratory Standard. Occupational Exposure to
Hazardous Chemicals in Laboratories. 29 CFR 1910.1450.
S AWYER CN, M C C ARTY PL, P ARKIN GF (1994), Chemistry for Environmental Engineering, McGraw-Hill,
NY.
S MITH R-K (1997), Handbook of Environmental Analysis, 3rd Edition, Genium Publishing Corporation,
Amsterdam, NY.
US EPA (1983), Methods for Chemical Analysis of Water and Wastes, EPA/600/4-79/020.
US EPA (1983), Test Methods for Evaluating Solid Wastes Physical/Chemical Methods. SW-846 Method
On line: http://www.epa.gov/epaoswer/hazwaste/test/main.htm
W ILLIAMS I. 2001. Environmental Chemistry, John Wiley & Sons, NY West Sussex, England.
QUESTIONS AND PROBLEMS
1. Define the following terms: aqua regia, acid bath, acetone wash, Type I water, reagent
water, PPE, MSDS, primary standard, Mohr pipet, mineral acidity.
2. Illustrate how to prepare 2 N HCl and 2 N H 2 SO 4 solutions from concentrated HCl and
H 2 SO 4 .
3. Explain why K 2 Cr 2 O 7 has to be used to calibrate the concentration of Na 2 S 2 O 3 5H 2 O
which is commonly used in titration.
4. What does it mean if a pipet is labeled as ''5 in 1/10 mL, TD 20 C''?
* Suggested Readings