Correct use of burettes

Titration analysis, also known as volume analysis, is the dropwise addition of a standard solution of known accurate concentration to the solution of the measured substance until the measured substance is completely reacted with the added standard solution, and then the content of the substance is calculated according to the volume and concentration of the standard solution. The precise measurement of liquid volume is an important operation in titration analysis and an important factor in obtaining good analytical results, for which it is essential to understand how to use volumetric analysis instruments correctly.

Burette is a glass instrument that can accurately measure the volume of titrant consumption during titration, it is a slender glass tube with a precision scale and uniform inner diameter, which can continuously discharge different volumes of liquid according to needs and accurately read out the volume of liquid.

Depending on the length and volume, burettes can be divided into macroburettes, semi-microburettes and microburettes.

The volume of the macroburette is 50 mL, 25 mL, the minimum scale is 0.1 mL, and the minimum readable is 0.01 mL. The semi-microburette volume is 10 mL, the scale is minimum 0.05 mL, and the minimum readable is 0.01 mL. Its structure is generally similar to that of a constant burette. Microburette volumes are available in 1mL, 2mL, 5mL, and 10mL, with a minimum scale of 0.01mL and a minimum readable of 0.001mL. There is also a semi-micro semi-automatic burette, which can automatically dosing the liquid, but the titration still needs to be controlled manually.

Burettes are generally divided into two types, acid burettes and basic burettes.

Acid burette, also known as stopper burette, has a glass stopcock switch at the lower end, which is used to hold acidic solution and oxidizing solution and salt solution, and cannot contain alkaline solution such as NaOH. Basic burette, also known as stopperless burette, has a rubber tube at the lower end, and a glass bead in the middle to control the flow rate of the solution, it is used to hold alkaline solution and non-oxidizing solution, and the solution that can function with the rubber tube can not be loaded into the basic burette, such as KMnO4, K2Cr2O7, iodine solution, etc. Due to the use of PTFE pistons that are not afraid of alkali, the shortcomings of ordinary acid burettes are overcome and the acid burette can be universal to acid and alkali, so the use of basic burettes is greatly reduced.