Titration microscale

New. A new microscale titration experiment is included, provided by Professor John Richardson from Shippensburg State University, for the analysis of hard-water samples (Experiment 18). The tools an4 techniques used for that experiment could be used to design similar experiments for other titrations if desired. (If your in-stractor tries this with you, I may include your experiment in the next edition ) Two team experiments are added (Experiments 39 and 40) to illustrate the principles presented in Chapter 4 on statistical validation. One is on method validation and quality control, in which different members of teams perform different parts of the validation for a chosen experiment. The other is on proficiency testing, in which you calculate the z-values for all the student results of one or more class experiments and you compare your z-value to see how well you have performed. 

The other analytical methods necessary to control the typical specification given in Table 5 are, for the most part, common quality-control procedures. When a chemical analysis for purity is desired, acetylation or phthalation procedures are commonly employed. In these cases, the alcohol reacts with a measured volume of either acetic or phthalic anhydride in pyridine solution. The loss in titratable acidity in the anhydride solution is a direct measure of the hydroxyl groups reacting in the sample. These procedures are generally free from interference by other functional groups, but both are affected adversely by the presence of excessive water, as this depletes the anhydride reagent strength to a level below that necessary to ensure complete reaction with the alcohol. Both procedures can be adapted to a semimicro- or even microscale deterrnination. 

Microscale student experiments reduce costs by decreasing consumption of reagents and generation of waste. An inexpensive student buret can be constructed from a 2-mL pipet graduated in 0.01-mL intervals.15 Volume can be read to 0.001 mL and titrations can be carried out with a precision of 1%. 

A last example of microscale metal atom chemistry makes an important link with the macroscale experiment. A low temperature form of a complex between iron and toluene has been identified(34) in cocondensates formed at 77K. Controlled warming converts the product to a high temperature species, stable in the liquified complex/toluene/methylcyclohexane solution. Apparently, the same high temperature complex can be formed directly by iron atom titrations of a 10% toluene/methylcyclohexane solution at 150 K. The high temperature form begins depositing colloidal iron above -30°C. 

EXPERIMENT 18 MICROSCALE QUANTITATIVE ANALYSIS OF HARD-WATER SAMPLES USING AN INDIRECT POTASSIUM PERMANGANATE REDOX TITRATION ... 

The development of ultrasensitive calorimeters enabled ITC to perform microscale measurements of biological samples, such as protein and DNA. However, even the most sensitive models currently available still require milliHter or himdreds of microlitter volumes of reagents in micromolar to millimolar concentration for each titration experiment. Thus, the application of HC may be limited by the availability of reagents. 

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