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Q. |
How much time (in a minute) is usually required for the passing of Co2 through the mould? |
A. | one |
B. | two |
C. | five |
D. | seven |
Answer» A. one | |
Explanation: in co2 moulding, mould of sand is hardened by passing of co2 for about one minute. the co2 gas forms a weak acid that hydrolyzes the sodium silicate (na2o, sio2) solution to form amorphous silica gel which acts as the bond and sodium silicate itself also provides some bonding action. |
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