Volume as a signal

Almost any chemical reaction can serve as a titrimetric method provided that three conditions are met. The first condition is that all reactions involving the titrant and analyte must be of known stoichiometry. If this is not the case, then the moles of titrant used in reaching the end point cannot tell us how much analyte is in our sample. Second, the titration reaction must occur rapidly. If we add titrant at a rate that is faster than the reaction s rate, then the end point will exceed the equivalence point by a significant amount. Finally, a suitable method must be available for determining the end point with an acceptable level of accuracy. These are significant limitations and, for this reason, several titration strategies are commonly used. 

A simple example of a titration is an analysis for Ag+ using thiocyanate, SCN , as a titrant. 

This reaction occurs quickly and is of known stoichiometry. A titrant of SCN is easily prepared using KSCN. To indicate the titration s end point we add a small amount of Fe + to the solution containing the analyte. The formation of the red-colored Fe(SCN) + complex signals the end point. This is an example of a direct titration since the titrant reacts with the analyte. 

If the titration reaction is too slow, a suitable indicator is not available, or there is no useful direct titration reaction, then an indirect analysis may be possible. Suppose you wish to determine the concentration of formaldehyde, 1T2CO, in an aqueous solution. The oxidation of 1T2CO by 

This type of titration is called a hack titration. 

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The use of weight instead of volume as a signal for titrimetry is reviewed in the following paper. 

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