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VERIFICATION OF VOLUMETRIC GLASSWARE

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nina elyana zulkipli

on 27 November 2013

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Transcript of VERIFICATION OF VOLUMETRIC GLASSWARE

VERIFICATION OF VOLUMETRIC GLASSWARE
SOP AO3 015

INTRODUCTION
From the 16th century to today, chemical researchers have used glass containers for a very basic reason: the glass container is transparent, almost invisible and so its contents and reactions within it are clearly visible.

INTRODUCTION
GLASS: THE INVISIBLE MATERIAL
Because glass need to be heated or cooled or mix chemical substances. A chemistry laboratory requires special heat and chemical resistant glass.
In Microbiology analysis, ordinary glasses often leach toxic sunstances that can be harmful to growing cells, so microbiologist require glasses with low levels of extractables.
 Ordinary beakers and flasks are not used for accurate volume measurements; the markings on these pieces of glassware are generally only accurate to within 5%

SAFETY HANDLING GLASSWARE
New glassware should be soaked several hours in acid water (1% solution of HCL or HNO3 ) before washing
Never apply heat directly to empty glassware used for volumetric measurement
Temperature for drying not more than 800 C in short time only.
Autoclaving- Streilization time should not exceed 15 minutes at 1210 C and drying time should not exceed 15 minutes at 1100 C
Not advisabe to expose to temperature below -200 C,
may effect on coating

GLASS: THE INVISIBLE MATERIAL
GLASSWARE
It can be divided into TWO groups
Non-Volumetric Glassware
BEAKER
FLASK
Volumetric Glassware
Volumetric Flask
Graduated Cylinder
VOLUME MEASUREMENT
Pipets
Burets
Volumetric flask
Measuring cylinder
Syringe???
Wash buret with new solution
Eliminate air bubble before use
Drain liquid slowly
Deliver fraction of a drop near end point
Read bottom of concave meniscus
Estimate reading to 1/10 of a division
Avoid parallax
Account for graduation thickness in readings
BASIC PRINSIPLE OF GLASSWARE CALIBRATION
TO CONTAIN
(TC)
Will contain the specified amount when filled to the capacity mark
Will not deliver that amount
Adhesion to sides
TO DELIVER
(TD)
Marked slightly differently so that it does deliver the specified amount, assuming the liquid is water at 20'C (TWENTY DEGREE) and it is poured using specific techniques
Example:
Volumetric Flask
- Hold specific volume
- Essential for proper concentration of buffer
- Not good for 'DELIVERING' proper volume
- Used of TD device should be used
OPERATING A BURRETTE
PROPER TECHNIQUE OF TITRATION
Place the flask on a white background
Place the buret tip in the neck of the flask while your swirl
Position the black field just below the meniscus
Avoid parallax error by reading at eye level
A 50 mL buret can be read to ±0.01 mL, but in order to be able to interpolate to the last digit, the perpendicular line of sight must be followed with meticulous care
READING THE MENISCUS
AVOID PARALLAX

A volumetric flask is calibrated to contain a particular volume of solution at 20'C when the bottom of the meniscus is adjuzted to the center of the mark on the neck of the flask
VOLUMETRIC FLASKS
Glass is notorious for adsorbing traces of chemical especially cations. Adsorption is the process in which a substance sticks to a surface. (In contrast, adsorption is the process in which a substance is taken inside another, as water is taken into a sponge.

For critical work, you should acid glassware to replace low concentrations of cations on the surface with H+.
PROPER USAGE OF VOLUMETRIC FLASK
Pipette deliver known volumes
Transfer pipette
Measuring pipette
PIPETTE AND SYRINGE
Designed to transfer a fixed amount of liquid when filled to the mark, e.g. 10 mL and only 10 mL
There is generally only one "fill-line" on a volumetric pipet
For example a 5 mL volumetric pipette has one marking on it. This marking measures exactly 5 mL of liquid, no more, no less

Measuring pipette are straight-bore pipette marked at different volumes
They are less accurate than volumetric pipettes
Transfer Pipette
To deliver one fixed volume
More accurate

Measuring Pipette
Deliver variable amounts

For rapid measurement of liquid volume
They are generally more accurate and precise for this purpose than flasks
This is a semi-accurate liquid measuring vessels
EXAMPLE OF PIPETTES
TRANSFER PIPETTE
GRADUATED CYLINDER
1O mL has approx 6.62 mL
100mL has 52.7 mL
25mL has 11.5 mL
READING THE VOLUME
CALIBRATION OF VOLUMETRIC GLASSWARE
Calibration is the process of measuring
the actual quantity of mass, volume and so on that corresponds to an indicated quantity on the scale of the instrument
Correction of Thermal Expansion
EXERCISE
Q & A SESSION!
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