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meniscus line
Asimple definition of meniscus is the
curve on the surface of the liquid.
According to
DIN
,
ISO
andmost other
standards volume should be read at
the lowest liquid level.
The lowest level of the meniscus has
to touch the upper edge of the
graduation mark.
On the volumetric glassware the form
of the meniscus is concave.
For the exact and most precise
results, the eye of the observer must
be exactly at the same level of
meniscus line.
To have a better, faster and more
accurate reading and measurement,
a black strip should be held at the
back side, just belowof the graduation
mark and meniscus line.
black paper
graduation
line
meniscus
line
classification
All volumetric products are always
calibrated as
to contain (In)
or
to
deliver (Ex)
.
They are classified in two groups;
Class “B”
or
Class “A”
or
“AS”
.
Class “A”
and
“AS”
carries exactly
the same error and tolerance limits.
The difference is in their “delivery”
and “waiting times”. “S” means quick
(swift) delivery.
The classification as
“A”
or
“B”
indicates the degree of accuracy of
related parameters.
Class “A”
or
“AS”
volumetric
products carries highest level of
accuracy and specially well accepted
by laboratories looking for quality.
The error limits, accuracy and
variations are always according to
related
ISO
or
DIN
standard limits.
The waiting time starts after
complete transfer is finalised.
After the transfer of the liquid usually
liquid continues to flow down from
the burette or pipette wall.
For accurate volume measurement
attention must be paid to the
waiting time.
Specially with pipettes the residual
drop accumulated at the tip should
be considered.
waiting time
Delivery time is the time needed to
deliver the liquid from the starting
level to the final level.
For burettes and pipettes final level
is generally the tip of the product.
delivery
time
The schellbach stripe is a narrow
blue band which takes place at the
center of a wider white band on the
burette tube backround.
Mostly printed at the backside of the
burette tube for easier observation
of meniscus line.
schellbach stripe
Thepenetrated light fraction twoarrow
head points that appear at the
meniscus line.
Exact meniscus line is exactly where
two arrow heads touch each other.