Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, CO

The Determination of WaterA Spectrophotometric Titration

Joseph A. DiVerdiQuantitative Analysis Laboratory - CHEM 334

Department of ChemistryColorado State University

29 November & 2 December 2016

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COCommon Problem & Need

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COUbiquitous Measurement

• Measured in many systems• Ours is sodium bis(ethylhexyl)sulfosuccinate

Also known as: AOTAn anionic surfactant useful in forming micellesKnown to be hydroscopic and contains an undetermined

amount of water as received from supplier

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COStandard Methods

• Karl Fisher Titration– SO2, pyridine and iodine (Ugh)

• IR spectroscopy– Good method, expensive instrument

• NMR spectroscopy– Great method, more expensive instrument

• Spectrophotometry– Intriguing method

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COSpectrophotometric Titration

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COReaction & Method Details

- Start out with acetic acid(l) containing some water in the titration vessel.- Add acetic anhydride which consumes water until no water remains.- Additional acetic anhydride results in absorption at 256 nm.

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COSpecified Procedure

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COActual Method Used

- Recording UV-Vis spectrometer- Cuvette with stirring disk- Microsyringe injection (repeating)

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, CORaw Experimental Data

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COReduced Experimental Data

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COBlank Computations

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COAOT Raw Data

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COAOT Reduced Data

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COAOT Computations

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COOther Titrations Possible

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COAdditional Considerations

Upper-Division Chemistry Laboratories2016 – CSU Fort Collins, COAcknowledgements

- Kai Fuller, undergraduate research student

- Financial Support from the Department of Chemistry