CY6251 CHEM 2 Notes, Engineering Chemistry 2 Lecture Notes – IT 2nd SEM Anna University


Anna University Regulation 2013 Information Technology (IT) CY6251 CHEM 2 Notes for all 5 units are provided below. Download link for IT 2nd SEM CY6251 Engineering Chemistry 2 Lecture Notes are listed down for students to make perfect utilization and score maximum marks with our study materials.


Internal treatment involves adding chemicals directly to the water in the boilers for removing dangerous scale – forming salts which were not completely removed by the external

Treatment for water softening. This method is used to convert scale to sludge which can be removed by blow-down operation.

Calgon conditioning

Carbonate conditioning

Phosphate conditioning

Colloidal conditioning

Calgon conditioning

Calgon is sodium hexa meta phosphate with a

Composition Na2(Na4 (PO3)6). A highly soluble complex containing Ca is formed by replacing the sodium ions and thus prevents their formation of scale forming salts like CaSO4. The reaction is as follows:

2CaSO4 + Na 2 [Na 4 (PO3) 6] → Na 2 [Ca 2 (PO3) 6] + 2Na2SO4

Since the complex is highly soluble there is no problem of sludge disposal.

Carbonate conditioning

Scale formation due to CaSO4 in low pressure boilers can be avoided by adding Na2CO3 to the boilers.

CaSO4 + Na2 CO3 → CaCO3 + Na2SO4

The forward reaction is favored by increasing the concentration of CO3 2- .CaCO3 formed can be removed easily.

Phosphate conditioning

In high pressure boilers, CaSO4 scale whose solubility decrease with increase of temperature. Such scale can be converted into soft sludge by adding excess of soluble phosphates.

3CaSO4 + 2Na3 PO4 → Ca3 (PO4)2 +2Na2SO4

There are three types of phosphates employed for this purpose.

Tri-sodium phosphate – Na3PO4 (too alkaline): used for too acidic water.

Di-sodium hydrogen phosphate – Na2HPO4 (weakly alkaline): Used for weakly acidic water.

Mono sodium di hydrogen phosphate NaH2PO4 (acidic) used for alkaline acidic water.

Colloidal conditioning

The colloidal conditioning agents are kerosene, agar-agar, gelatin, glue, etc. They are

Used in low pressure boilers.

The colloidal substances convert scale forming substance like CaCO3, CaSO4 into a Non-adherent, loose precipitate called sludge, which can be removed by blow-down Operation.


Caustic embrittlement is a form of corrosion caused by a high concentration of sodium Hydroxide in the boiler feed water.

It is characterized by the formation of irregular intergranular cracks on the boiler metal, particularly at places of high local stress such as bends and joints.

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