Once the buret has been rinsed with water and the titrant solution, then the

buret can be filled with the titrant solution. Make sure the liquid level is within

the volume markings and that the tip of the buret is filled with liquid and does

not contain an air bubble.

Analyte Preparation

In a titration, the chemical we are trying to quantify (analyte) is either a solid or

in a solution. For a titration to work appropriately, we need the analyte to be

dissolved in a solution. If you have a solid analyte the first step is to dissolve it in

a solvent (very often water).

Since we are trying to be quantitative in this technique, it is also critical to know

the amount of analyte we are using during the titration. If the analyte is a solid,

then the easiest approach is to measure the mass of solid using a balance. If the

analyte is a solution, then the easiest approach is to use a volumetric pipet to

know the volume of analyte that will be titrated.

One other factor to keep in mind when we are preparing an analyte is that we

want to ensure that we have an appropriate amount of analyte for the titrant

solution being used. In general, we want the titrations to require somewhere

between 10 and 50 mL of solution delivered from the buret. This is because most

burets can at most deliver a maximum of 50 mL before being refilled. We also

want the titration to take at least 10 mL so that we get smaller uncertainties and

more significant figures for the measurement.

Indicator

For the titration to work, we need some way of determining when we have added

exactly the right amount of titrant to completely react with the analyte.

Indicators are the common approach to determine when we have reached the

equivalence point. For the titrations we are performing in this laboratory (acid as

the analyte and base as the titrant), we will use an acid-base indicator that is

one color at low pH values and a different color at high pH values.

Phenolphthalein is a commonly used indicator because it is colorless when the pH

is below 8.3 and is pink when the pH is above 8.3.

As we add a base to solution the pH will increase. In a titration where the analyte

is an acid the pH will remain low until all of the acid has reacted and then it will

rise rapidly. The goal of the indicator is to show us exactly when all the acid has

reacted by changing color. We want to control our delivery of the titrant, so the

indicator in the solution goes from colorless to pink when just one drop or less of

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