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Buret Clamp

 Buret clamp used in laboratory

1. What is buret clamp?
    1.1 Buret clamp
    1.2 Buret and buret clamp
    1.3 What is chemical titration?
    1.4 How to titrate?
2. Types of buret clamp
3. How to buy buret clamp?

What is buret clamp?

Buret clamp

A buret clamp is a clamp used to hold a burette. Usually, the burette clamp should be fixed on a steel stand. It is better to put a piece of soft rubber tube on the part of the burette clamp in contact with the burette to prevent the burette from being pinched and falling off.

Buret and buret clamp

A buret is a glass instrument that can accurately measure the volume of titrant consumed during a chemical titration. It is a thin glass tube with a precise scale and inner diameter, which can continuously discharge different volumes of liquid as needed and read out the volume of liquid accurately as a measuring instrument.

Depending on the length and volume, burets can be divided into constant burets, semi-micro burets, and micro burets.

According to the usage, buret is generally divided into two types - acid buret and alkaline buret.

Acid burette is also called burette with stopper, which has a glass stopper switch at the lower end. It can be used for acidic solutions, oxidizing solutions & salts, but not for alkaline solutions such as NaOH.

The alkaline burette, also known as the uncorked 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 typically used for alkaline solutions and non-oxidizing solutions, but the solution that works with the rubber tube cannot be loaded into the alkaline burette, such as KMnO4, K2Cr2O7, iodine solution, etc. Since the use of alkali-resistant Teflon piston overcomes the disadvantage that ordinary acid buret is not resistant to alkali, acid buret can be made universal which causes the frequency of use and application places of alkali buret to be greatly reduced.

When having a chemical titration, the burette should be clamped vertically to the burette holder.

What is chemical titration?

Chemical titration analysis, also called volumetric analysis, is the process of adding a standard solution of known exact concentration dropwise to a solution of the substance to be measured until the substance to be measured reacts completely with the standard solution added and then calculating the amount of the substance based on the volume and concentration used in the standard solution. The precise measurement of the volume of the liquid is an important operation in titration analysis and is an important factor in obtaining good analytical results. For this reason, it is important to understand how to properly use volumetric analysis instruments.

Here following are some titration instruments or the instruments needed to configure the standard solution that we should know:
a. Buret clamp: used to hold the burette.
b. Burette (acid or alkaline): used to hold the standard solution.
c. Conical flask: used to hold the tested sample and as a reaction vessel.
d. Iron stand: used to fix the burette clamp.
e. Pipette: used to pipette the sample to be measured.
f. Volumetric flask: used to configure the standard solution.
g. Glass rod: used to stir the solution and transfer the solution.
h. Beaker: The container for dissolution operation.
i. Pipette: used to fix the volume.
j. Balance: weighing reagents – solids.
k. Measuring cylinder: used to measure reagents – liquids.

Titrimetric analysis, which has high accuracy in the analysis of macronutrients. It is one of the most commonly used quantitative methods in the laboratory. Chemical reactions suitable for titrimetric analysis should have the following conditions:

1) The reaction must be completed quantitatively according to the equation, usually requiring 99.9% or more, which is the basis for quantitative calculations.

2) The reaction can be completed rapidly (sometimes heat or a catalyst can be used to accelerate the reaction).

3) Coexisting substances do not interfere with the main reaction, or their interference is eliminated by an appropriate method.

4) There is a relatively easy way to determine the measurement point (indicating the end point of the titration).

Common titration analysis methods

a. Acid-base titration
Among all titration analysis methods, acid-base titration is the most basic. “Acid-base equilibrium” means the essence is the proton transfer between acid and base.

b. Coordination titration method
It mainly refers to the structure, properties, coordination equilibrium, stability constants of EDTA, as well as titration curve, selection of indicators, and methods to eliminate interference.

This method focuses on “ligand equilibrium”. In coordination titration, except for the main reaction, there are various side reactions that interfere with the main reaction, which have a great influence on the coordination equilibrium.

c. Redox titration
The core of redox titration is still in “equilibrium”, which is based on electron transfer, and the reaction conditions have a great influence on the equilibrium, too.

d. Precipitation titration
The core of the precipitation titration method is the precipitation equilibrium. Its main method is called the silver measurement method, which can be subdivided into the molar method, Faulhard method, and adsorption indicator method depending on the method used to determine the endpoint.

e. Connections and differences between acid-base, coordination, redox, and precipitation titrations.
The common feature of those titration analysis methods is the measured ion concentration shows a regular change during the titration process. As long as the focus is on mastering the pH calculation during the acid-base titration, the other titration methods can be solved in the same way.

How to titrate?

Preparation of the burette before use

a. Leakage check
After washing the buret, it is a priority to check whether the rotation of the cork is flexible to avoid water leakage. You should close the cork, fill the buret with water, and check around the cork and the tip of the tube with filter paper to check whether it is leaking or not. Then you should rotate the cork 180 degrees, let the buret stand upright for two minutes, and check with filter paper. If water leaks, you should use petroleum jelly to coat the acid tube; the alkaline type burette should be checked before use to see if the rubber tube is aging and if the glass beads are of proper size. If there is any problem, the piston should be replaced promptly with petroleum jelly.
b. Washing of burettes
The burette must be washed before use and the inner wall of it cannot be damaged.

Before washing the burette, you should close the cork first and pour about 10mL of washing solution into it. Then open the cork, release a small amount of washing solution to wash the tip of the burette, and tilt it to the mouth while turning to let the washing solution covers the whole inner wall. Finally, release the washing solution out of the burette and rinse with tap water three times, 10-15mL each time.

The washing method of the alkaline burette is different from that of the acid burette. The alkaline burette can be washed by removing the tip of the tube with the glass beads and dipping it into the washing solution. The tube is placed upside down into the washing solution and washed with a rubber pipette bulb.
c. Rinse
After washing the burette with tap water three times, it must be washed three times again with the titrated solution before use, 10-15mL each time.
d. Fill liquid to exhaust bubble
After rinsing, inject the titrated solution above the zero line and check if there are bubbles around the piston. If there are bubbles, open the large piston to flush out the solution and exhaust the air bubbles. The titrated solution must be injected directly without any auxiliary container, like funnels.

Alkaline burette bubble discharge method: you should hold the alkaline burette tube body upright, pinch the glass beads with the left thumb, bend the rubber tube, slope the tube tip up 45 degrees, and squeeze the rubber tube at the glass beads to make the solution flush out and exhaust air bubbles.
e. Initial reading
Wait for one to two minutes after releasing the solution before reading.

To take a reading, you should remove the buret from the buret clamp and keep the buret vertical by pinching the upper part where is no liquid with the left hand. The line of sight is tangent to the horizontal line of the scale at the lowest point of the liquid level. If the line of sight is above the liquid level, the reading will be high; if it is below the liquid level, the reading will be low. If the solution is colored, its liquid level is not clear enough, then read the highest point of it. Generally, the initial reading is at 0.00 degree or between 0 to 1mL degrees. This reading can reduce the volume error.


During the titration, the burette should be clamped vertically to the burette clamp and the burette base should be white. The buret should be about 1 cm from the mouth of the conical bottle. Hold the screw plug with the left hand, with the thumb in front, the middle finger of the index finger behind, and the ring and little fingers are bent at a right angle between the burette and the underside of the cock. When turning the cork, keep the fingers bent and the palm of the hand does not touch the cork. Hold the neck of the bottle with three fingers of the right hand. The bottom of the bottle is about 2-3cm from the base. The lower end of the burette is deep into the mouth of the bottle about 1cm. Shake the conical flask by slightly moving the right wrist joint, shaking while dropping to make the solution mixed evenly.

The liquid flow rate is from fast to slow. At first, it is possible to "form a line with drops", then drop by drop, and when the endpoint is reached, it is necessary to add half drops by half drops.

When the indicator in the conical bottle indicates the endpoint, close the piston immediately and stop the titration. Wash the inner wall of the conical bottle. Remove the burette, hold the upper part of the burette where is no liquid with the right hand vertically, and read the liquid level by eyes. The reading should be estimated by one digit.

At the end of the titration, the remaining solution in the burette should be poured out. Wash the burette and set it aside on a clamp.

Type of buret clamp

Double burette clamp


Burette clamp double


Double buret clamp chemistry


How to buy buret clamp?

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