Explain how your text above will show when the BaSO_4 no longer has adsorbed impurity ions on its surface. The washed BaSO_4 precipitate must be quantitatively transferred from the beaker onto the filter paper for ashing. Use your wash bottle and a rubber policeman on the end of a glass stirring rod to squirt and scrape all of the solid barium sulfate from the beaker onto the filter paper. Quantitative transfer of the precipitate requires that oil solid particles adhering to the beaker or the rubber policeman be transferred to the filler paper. Once all the precipitated barium sulfate has been collected on the filter paper, carefully remove the paper from the funnel without tearing it and gently fold it into a loose "package." Place the filter paper and its contents in the dry, cooled, pre-weighed crucible. Use a low burner flame to heat the crucible supported in the triangle until the paper is dry. Once the paper is dry, gradually increase the burner flame to char the filter paper without allowing it to ignite. Once the paper is completely charred, continue heating the crucible strongly until the paper has been completely ashed and any black carbon residue from the paper has disappeared. (It reacts with the air, forming carbon dioxide gas and water vapor). Once the paper is completely ashed and nothing but solid white barium sulfate remains, cover the crucible and cool it to room temperature. Weigh the crucible and its contents without the cover. In this experiment, we use special ashless filler paper designed for quantitative analysis. How would your final weighing be affected if the paper used were not ashless? Return the crucible to the triangle and heat it for an additional five (5) minutes and then cool and weigh it again. Repeat this process until two successive weighings differ by no more than 0.004 g. (This technique is referred to as "heating to constant weight") Collect data from the person who has the same unknown number as you do and with whom your instructor has asked you to share data and record his or her data next to your own in the table on the next page.