Titration is a quite sensitive analytical method that lets us determine an unknown concentration of a chemical in solution by introducing a known concentration of another chemical. Several factors can cause errors in titration findings, including misreading volumes, mistaken concentration values or faulty technique.
There are plethora of sources of errors to occur in due course of titration. It can be either of end point error, misreading volumes, concentrations, faulty use of equipment, contaminated glass ware, etc. Some of errors are :
- Misjudging the color of the indicator near the end point - this is probably the most common one. Sometimes colour change is delicate and slow and not everyone have the same sensitivity to colours.
- Transferring of two different solutions using a same pipette and not rinsing pipette with distilled water in between.
- Using solutions of wrong concentration - titrant we use may have different concentration then expected. This can be due to incorrect standardization, error in copying the concentration, contamination of the bottle content, titrant decomposition, solution being kept in open bottle and partially evaporated and so on.
- Uncleaned equipments.
- Rinsing burette and/or pipette with wrong solution - if the burette or pipette is not dry before use, it has to be rinsed with the solution that will be transferred. Using just distilled water for rinsing will mean transferred solution is slightly diluted. Obviosuly it is important only when transferring sample, titrant or stoichiometric reagents used for back titration.
- Transferring excess volume of liquid - by blowing pipette for example, or by incorrectly leveling meniscus with the mark on the single volume pipette.
- Leaking burette - sometimes burettes leak slowly enough to allow titration, but will loose several tenths of milliliter if left for several minutes after titrant level has been set to zero and before titration started.
- Titrating at wrong temperature and wrong pH value - as several indicators are quite sensitive.
- Other human or equipment errors can also creep in. Human error includes using selecting the wrong reagents or using the wrong amount of indicator. Equipment error typically is in the burette, which can develop leaks over time. Even a small loss of fluid will affect the results of the titration.
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