Method of test for building limes Determination of carbon dioxide content
1973 Edition

To prepare lime samples for carbon dioxide testing according to IS 6932 Part 2, begin by accurately weighing approximately 2.5 grams of the lime sample. Transfer the sample into flask D, add between 20 to 40 milliliters of distilled water, and seal the flask using a glass stopper equipped with a funnel and condenser, ensuring an airtight setup. Pass air through the apparatus until the carbon dioxide absorption tubes (identified as 71 and 7) reach a stable mass. Subsequently, introduce 40 milliliters of hydrochloric acid into the flask via funnel C. Heat the flask to release gases through a sulfuric acid bubbler and maintain boiling for 30 to 40 minutes. After 2 to 3 minutes of boiling, remove the heat source, connect scrubbers A and B, and continue passing air for 20 minutes. Allow the absorption tubes to rest at room temperature for 30 minutes before weighing them again. The increase in the absorption tubes' mass corresponds to the carbon dioxide content in the sample. This method guarantees precise measurement of CO2 through gas absorption and gravimetric analysis.

The determination of carbon dioxide content requires specific equipment and chemicals. Apparatus includes flask D fitted with a glass stopper that holds a funnel and condenser, a stopcock to regulate airflow, carbon dioxide absorption tubes labeled 71 and 7, a sulfuric acid bubbler, scrubbers A and B, and a precise weighing balance capable of detecting small mass changes. Air supply is necessary to pass through the system. The reagents needed are distilled water complying with IS 1070-1970 standards, 40 milliliters of hydrochloric acid meeting revised specifications, and sulfuric acid for the gas bubbler. The procedure involves weighing approximately 2.5 grams of the lime sample with distilled water in flask D, passing air until the absorption tubes reach constant weight, adding hydrochloric acid to release CO2, and finally measuring the mass increase in the absorption tubes to determine CO2 content.

According to IS 6932 Part 2 (1973), carbon dioxide content in building lime is determined by weighing about 2.5 grams of the sample, placing it in flask D with 20 to 40 milliliters of distilled water, and assembling the airtight apparatus with absorption tubes. Air is passed through until tubes achieve constant mass. After adding 40 milliliters of hydrochloric acid and heating to release CO2 gas, the gases pass through a sulfuric acid bubbler during boiling for 30 to 40 minutes. Following boiling, air is passed for an additional 20 minutes through scrubbers. The absorption tubes are then cooled at room temperature for 30 minutes and weighed again. The CO2 content is calculated by the formula: CO2 (%) = (Mass increase of absorption tubes / Mass of sample) × 100. Results are rounded according to IS 2:1960 standards and reported as a percentage by mass of the lime sample.

To accurately measure carbon dioxide content in building lime per IS 6932 Part 2, the following steps are essential: accurately weigh approximately 2.5 grams of the lime sample; transfer to flask D and add 20 to 40 milliliters of distilled water; assemble the airtight apparatus with a glass stopper, funnel, and condenser; pass air until the CO2 absorption tubes reach constant mass; add 40 milliliters of hydrochloric acid through funnel C; heat the flask to release CO2 gas, allowing gases to pass through a sulfuric acid bubbler while boiling for 30 to 40 minutes and continuing for 2-3 minutes; remove heat and connect scrubbers A and B; pass air for 20 minutes at a moderate rate; finally, allow the absorption tubes to rest at room temperature for 30 minutes before weighing. The increase in mass indicates the CO2 content. This ensures complete reaction and reliable gravimetric determination.

IS 6932 Part 2 focuses specifically on the test method for determining carbon dioxide content in building lime. Originally part of IS 712-1964, which covered various lime tests, it was separated for clarity. Sample preparation aligns with Clause 7.2 of the latest IS 712 revision. The standard references additional Indian Standards such as IS 712:1984 for building lime specifications, IS 1070:1992 for reagent grade distilled water quality, and IS 265:1993 for chemical analysis methods. Reporting and rounding of results adhere to IS 2:1960 protocols. Together, these standards ensure consistent, accurate, and reproducible assessment of lime quality in construction applications.