Lab E2 Flashcards
Three types of precision calibrated glassware are always in use, what are these?
Burets
Pipets
Volumetric Flasks/Volumetric Glassware
What level should you read the solution in Volumetric Glassware?
Why?
Meniscus
To avoid Parallax Error (cause by change in observational position)
The curvature of the liquid surface on a narrow container
Level of concave is read on?
Level of convex is read on?
Readings on dark/colored liquid?
Liquid’s meniscus
Bottom of meniscus
Top of meniscus
Edge of the liquid
Isa flat bottom flask with a narrow neck.
Used to measure the very precise volume of solution.
Used to prepare solution of known concentration
Volumetric Flask
Elongated glass blub with two narrow glass stems at the top and bottom of the bulb.
Used to transfer volume of liquid
Two general types of glass pipets:
Pipet
Transfer Pipet
Measuring/Graduated Pipet
Used to transfer a fixed amount of liquid when filled to the mark.
It is either a ___________ which has bulb located at the middle
_________ which has bulb closer to the delivery tip, usually used for viscous liquid, like blood or serum.
Transfer Pipet
volumetric pipet
Oswald-folin pipet, usually for viscous fluids,
Used to measure variable volume.
Further classified into:
Has calibration marks that extend all of the way to the tip
Calibration marks that do not extend to the tip but the point above the tip
Measuring/Graduated Pipet
Mohr and Serological
Serological
Mohr
Serological pipet can be?
TC
TD
the contained quantity of the liquid corresponds to the capacity printed on the pipette.
the delivered quantity of the liquid corresponds to the capacity printed on the pipette.
TC-To Contain
TD-To deliver
Amount of liquid left on the pipet and to wet the inner surface
“___“Used when the pipet is adjusted to deliver
“___“Used when the pipet is adjusted to contain
The last drop of the TD pipet should be blown out, and TC is not
Drainage Holdback Error
Ex
In
False. TC-blown out
TD-not blown out
Sign of the pipet if it’s TC or TD
Double rings on the upper end of the pipet, indicate that it is BLOWN OUT/TC PIPET, should be blown using rubber bulb.
No ring-TD
Volumetric glassware which is used for accurate measuring of variable liquid reagent in a titration. It can be glass or plastic tube with graduation scale.
Buret
At the tip to control the flow of chemical solution
Barrel can be made:
Stopcock and Valve
Glass (Acid Buret)
Rubber Tube (Base Buret)
PTFE Polytetraflouroethylene (Teflon Buret)
Sign that the volumetric glassware cannot be used for accurate measurement
Exceeds correction factor
Experiment questions:
How to get the correction factor?
Apparent volume (capacity of pipet) - Actual volume (water)
- What is the importance and use of calibrating the volumetric glassware?
- What causes the volumetric glassware to deviate from its volume capacity?
- Name some basic techniques in proper handling of:
a) buret
b) pipet
c) volumetric flask
