Explore resources, experiments, and teaching materials shared by the analytical sciences community.
The simplest method for isolating a narrow band of radiation is to use an absorption filter, which work by selectively absorbing radiation from one or more regions of the electromagnetic spectrum. A […]
In Nessler’s original colorimetric method for ammonia, developed in the 1850s before the advent of spectrophotometers, the sample and several standard solutions of ammonia are placed in separate tall, flat-bottomed tubes. As […]
A source of electromagnetic radiation must provide an output that is both intense and stable. Sources of electromagnetic radiation are classified as either continuum or line sources. A continuum source emits radiation […]
The illustration here is a simplified energy diagram showing the absorption and emission of a photon by an atom or a molecule. When a photon of energy hν strikes the atom or molecule, […]
Illustration of plane-polarized electromagnetic radiation showing the oscillating electric field in red and the oscillating magnetic field in blue. The radiation’s amplitude, A, and its wavelength, λ, are shown. Normally, electromagnetic radiation […]
The most important class of indicators for redox titrations are substances that do not participate in the redox titration, but whose oxidized and reduced forms differ in color. When we add a […]
For an acid–base titration or a complexometric titration, the equivalence point is almost identical to the inflection point near the middle of the steeply rising part of the titration curve, which makes […]
If at least one species in a complexation titration absorbs electromagnetic radiation, we can identify the end point by monitoring the titrand’s absorbance at a carefully selected wavelength. For example, we can […]
Most indicators for complexation titrations are organic dyes—known as metallochromic indicators—that form stable complexes with metal ions. The indicator, Inm–, is added to the titrand’s solution where it forms a stable complex […]
Structures of (a) EDTA, in its fully deprotonated form, and (b) in a six-coordinate metal–EDTA complex with a divalent metal ion.
The illustrations below show two approaches to titrating very small samples. In the first experimental design, samples of 20–100 µL were held by capillary action between a flat-surface pH electrode and a stainless […]
In an acid–base titration the volume of titrant needed to reach the equivalence point is proportional to the moles of titrand. Because the pH of the titrand or the titrant is a […]
