A method for quickly identifying the authenticity of calcium formate

1.Introduction to Calcium Formate​

Calcium formate is a commonly used early strength agent to improve the early strength of cement. It is widely used in dry powder mortar. It has the properties of accelerating hydration and improving the early strength of mortar. Especially at low temperature, calcium formate can significantly improve the early strength of mortar.

​The effect of adding calcium formate to tile adhesive

Common packaging for calcium formate​

2.The role of calcium formate​

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Effect of calcium formate on properties of cement-based plastering mortar​

(1) Under normal temperature conditions, the 1d bond strength of the plastered mortar mixed with calcium formate is 45.7% higher than that of the unmixed one, and the 1d compressive strength is 49.0% higher; it shows that calcium formate can significantly promote cement under normal temperature conditions. The hydration improves the early strength of the mortar.

(2) Under low temperature conditions, the 1d bond strength of the plastered mortar mixed with calcium formate is 140% higher than that without the addition, and the 1d compressive strength is 83.8% higher. It shows that the effect of calcium formate on the early strength of mortar is particularly obvious under low temperature conditions.

3.Common low-priced counterfeit products in the market​

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Left: Calcium formate Right: Yuanming powder​

Substances commonly used in the market for adulteration include: sodium sulfate (sodium sulfate), industrial salt (sodium chloride), calcium chloride, etc. The early strength effect of these substances in dry powder mortar is much lower than that of calcium formate, and it will cause serious adverse consequences such as pan-alkali.​

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Pan-alkaline phenomenon of black caulk after misuse of sodium bicarbonate​

4.Simple identification method of calcium formate​

1. Judgment of loss on ignition​

The loss on ignition of calcium formate is between 20-30%, while the loss on ignition of sodium sulfate, sodium chloride and calcium chloride is less than 5%. The purity of calcium formate can be roughly judged according to the loss on ignition, and at the same time, it needs to be combined with ion titration for comprehensive identification.
Ignition loss test method: Weigh 3-5g sample into the muffle furnace, burn it at 650℃ for about 2 hours, take it out after cooling and calculate the result.

2. Ion titration judgment​

Titration principle​

Salts such as calcium formate can be completely dissolved in water and ionized, so the authenticity of calcium formate can be identified by chemical titration.

After calcium formate is dissolved in water, it can only ionize formate ions and calcium ions without other impurities. If other ions such as (SO42-, Cl-, etc.) are titrated out, it means that the purity of calcium formate is not high. According to the titration principle, we know that real calcium formate does not contain SO42- and Cl-, so we use the most basic ion reaction for mutual titration, that is, titrate Ca2+ with Na2CO3, titrate SO42- with BaCl2, and titrate Cl- with AgNO3. The authenticity of calcium formate can be judged according to the phenomenon.
Remember not to add Na2CO3, BaCl2 and AgNO3 at the same time

Ca2+的滴定

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Because Ca2+ will react with CO32- to form a precipitate, so dissolve “calcium formate” in water and add a certain amount of sodium carbonate during identification. If precipitation occurs, it means that there is calcium ion, but it does not prove that it is real calcium formate , because it may also be CaCl2, but also to determine whether it contains other impurity ions and the comprehensive loss on ignition.
Titration of SO42-

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Because SO42- will react with Ba2+ to form a precipitate, use BaCl2 to titrate whether it contains SO42-. If BaCl2 is added to the “calcium formate” aqueous solution and precipitate occurs, it means that it contains SO42-.
Titration of Cl-

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Because Cl- will react with Ag+ to form a precipitate, use AgNO3 to titrate whether it contains Cl-. If AgNO3 is added to the “calcium formate” aqueous solution to produce a precipitate, it means that it contains Cl-.

To quickly determine the authenticity of calcium formate, it is necessary to comprehensively determine the loss on ignition and ion titration!

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