Burette = (Am.) buret ; a graduated vertical glass tube used to deliver variable volumes of liquid or gas ; usually equipped with a stopcock to control the liquid flow. Buret reading tips : Read the bottom of the concave meniscus You should always estimate the reading of any scale to the nearest tenth of a division. Avoid parallax ( 視差 ) Account for the thickness of the marking lines in your readings thickness of marking line = ca mL/ 50 mL buret volume of a drop = ca mL / 50 mL buret drainage rate = no more than 20 mL/min Washing any glassware with a new solution is a good idea. The air bubble often trapped beneath the stopcock of a buret should be expelled before use. The mass titration by a syringe is more accurate.

(a)Glass bead valve (b)Teflon valve Geissler Burette

Glass buret. Digital titrator with plastic cartridge containing reagent solution is used for analyses in the field. Battery-operated electronic buret with digital readout delivers 0.01 mLincrements from a reagent bottle.

An air bubble trapped beneath the stopcock should be expelled before you use the buret. Operating a buret. 1.Wash buret with new solution. 2.Eliminate air bubble before use. 3.Drain liquid slowly. 4.Deliver fraction of a drop near end point. 5.Read bottom of concave meniscus. 6.Estimate reading to 1/10 of a division. 7.Avoid parallax. 8.Account for graduation thickness in readings.

Buret and meniscus

Buret with the meniscus. Estimate the reading of any scale to the nearest tenth of a division mL

Buret volume (mL) Smallest Graduation (mL) Tolerance (mL)  or 0.02     0.10 Tolerance of Class A buret

Recommended method for manipulation a buret stopcock. 뷰렛에 적정용액 취하기

Volumetric flask : mess flask : measuring flask ; A laboratory flask primarily intended for the preparation of definite, fixed volumes of solutions, and therefore calibrated for a single volume only. TC 20 o C = calibrated to contain the indicated volume at 20 o C E : eingu  TD 20 o C = calibrated to deliver the indicated volume at 20 o C A : ausgu  Soak already thoroughly cleaned glassware in 3~6 M HCl in a fume hood for >1hr, followed by many rinses with distilled water. Volumetric flask

Class A glass volumetric flasks with glass stopper or Teflon stopper. Class B polypropylene plastic volumetric flask for trace analysis. Short-form volumetric flask with Teflon-lined screw cap fits.

Flask capacity (mL) Tolerance (mL) 1           0.50 Tolerance of Class A volumetric flask

The Lab Notebook The lab notebook must. State what was done. State what was observed. Be understandable to someone else Report  Date  Weather  Temperature  Humidity  Pressure  Name  Coworker  Objectives, chemical equations  Methods and procedure / Instrumentation and reagents  Results and discussions AConclusion A Reference

Summary Lab safety Chemical balance / tare, capacity, sensitivity, vernier, buoyancy, weights, tolerance, electromagnetic restoring system Drying / constant mass, desiccator, desiccant, ignition Filtration / crucible, vacuum filtration, decantation, policeman, ashless filter paper, mother liquor Transfer pipet Buret / meniscus, parallax Volumetric flask / TD, TC Lab notebook

Q n A Thanks. Dong-Sun Lee / 분석화학연구실 (CAT-Lab) / SWU.