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4/8/2020CHAPTER 2Chemicals, Apparatus, and UnitOperations of AnalyticalChemistry1Mechanical Analytical Balancex.xxxx g231
4/8/2020Semi-ElectronicAnalytical Balance4How does an modern electronic analyticalbalance work?photocellPan onhollow metalcylindercylindricalmagnet current keeping the pan in the null position is directlyproportional to the sample’s mass.5Fig 2-CO, p.2062
4/8/2020Forhygroscopicsolid andnoncorrosiveand relativelynonvolatileliquid transferTypical Weighing Bottles7A desiccator is a device fordrying substances or objects.Components of a typicaldesiccator. The basecontains a chemicaldrying agent, which isusually covered with awire screen and aporcelain plate withholes to accommodateweighing bottles orcrucibles,8Drying Agents;Conc. H2SO4Silica gelCaCl2CaSO4 (“Drierite”)Na2SO4 (10H2O)Color Indicator2H 2 O6H 2 OCoCl 2 CoCl 2 2H 2 O Co(H 2 O)6 Cl2Blue purple pink93
4/8/2020Photo of desiccator containingweighing bottles with dry solids10Arrangement for thedrying of samples.It shows the recommendedway to dry a sample. Theweighing bottle is contained ina labeled beaker with a ribbedcover glass.11Quantitative transfer ofsolid sample. Note theuse of tongs to holdthe weighing bottleand a paper strip tohold the cap to avoidcontact between glassand skin.Fig 2-10, p.32124
4/8/2020Fig 2-16, p.391314Typical pipets:(a) volumetric pipet,(b) Mohr pipet,(c) serological pipet,(d) Eppendorfmicropipet,(e) Ostwald-Folin pipet,(f) lambda pipet.155
4/8/2020Frosted ring“10 mL in 2/10”10 mL(10 0)0 810 mL(0 )(2 mL?)Serological Pipet16TDTCTD“TD”—to deliver“TC”—to containFig 2-22d, p.4517Should the last drop be blown out?--DependsUse of Volumetric PipettesTo deliver, allow the liquid to drain for 5 to 10 seconds afterthe liquid is vertically dispensed. Do not blow out. Touchthe pipet tip to the side of the receiving container.186
4/8/2020Reagents arenot stick tothe plasticmaterial?(e.g., Teflon?)Bottom line: Read the manual, consult the technicalsupport of the manufacture, or calibrate yourself.1920Fig 2-18b, p.42217
4/8/2020AirbubbleStopcocks2NaOH SiO2 « » Na2SiO3 H2O(Water glass/liquid glass)22xx.xx mLFig 2-21, p.4423Fig 2-22a, p.45248
4/8/2020Fig 2-22b, p.4525Table 2-3, p.4926279
Operations of Analytical Chemistry Mechanical Analytical Balance x.xxxxg 1 2 3. 4/8/2020 2 Semi-Electronic Analytical Balance How does an modern electronic analytical balance work? cylindrical magnet Pan on hollow metal cylinder photocell current keeping the pan in the null position is directly
