EHS > Chemical
> Programs & Guidelines
OF MERCURY THERMOMETERS
Public Act 578
of 2002 of the State of Michigan prohibits the sale or offer for
sale of mercury thermometers for use in the state after January
1, 2003. The act permits three exemptions:
- A use for
which a mercury thermometer is required by state or federal statue,
regulation or administrative rule;
- Mercury fever
thermometers dispensed by prescription.
If the thermometer
use does not meet one of the exemptions, a mercury free alternative
will need to be purchased.
Public Act 578
storage requirements for non-mercury thermometers
horizontally, such as in a drawer, non-mercury thermometers separate
more frequently than mercury thermometers. Ideally non-mercury thermometers
should be stored with the bulb lower than the expansion chamber,
however this is not always possible. Special drawer trays, which
will store the thermometers at the correct angle, can be purchased
from VWR (catalog numbers 61010-012 or 61222-502). These trays are
only 1.5 inches high and will fit in most drawers.
equivalent non-mercury thermometers
a replacement, take an inventory of the thermometers in your laboratory.
Remove mercury thermometers from areas where there is a high risk
of breakage such as heating blocks, drying ovens, water baths, and
refrigerators. Many times when a thermometer is broken in one of
these devices the first available thermometer is grabbed as a replacement.
Often it is an expensive thermometer, which may be used as your
replacement and it can be replaced with an inexpensive substitute.
the properties of the thermometer that was broken:
- Partial immersion/total
the properties needed for the application. When looking at alternatives
the tendency is to buy the most accurate with the largest range.
Most non-mercury thermometers do not have as large of a range as
mercury. The most cost-effective replacement may not exactly duplicate
the properties of the original thermometer but will meet the properties
required for the application.
Cost similar to mercury
Accuracy: Varies, similar to mercury
Range: -100 to 200o C
Often discounted by suppliers, most cost effective alternative
for water baths, ovens, and refrigerators.
Cost: comparable to, to substantially more than mercury depending
on range and accuracy.
Accuracy: Varies, similar to mercury
Range: -10 to 260 o C
Used successfully in many mercury replacement programs.
Cost: Comparable to mercury
Range: -10 to 225 o C
Chemistry has attempted to use these as a substitute in their
teaching labs. They experienced problems with reuniting separated
columns. Some of the liquid may remain on the walls of the capillary
tubing resulting in inaccurate readings.
Cost: Depends on the accuracy, some are comparable to Ever-safe.
Accuracy: Similar to much better than mercury
We are currently testing Fisher PN #15-078J in Chemistry. With
discount pricing it is comparable to the Ever-Safe thermometer
however it can be stored in a drawer without the separation problems
associated with non-mercury thermometers. Digital thermometers
are rapidly improving and decreasing in price. Do not dismiss
this alternative without consulting the most current information
to consider when purchasing a digital thermometer:
- How often
the reading is updated.
- The diameter
of the stem may be different than a traditional thermometer,
apparatus made need to be modified
- The orientation
of the display, it may be difficult to read in some applications
- The thermometer
housing or stem may degrade in the experiment.
separated non-mercury thermometers
recommend two different methods for reuniting non-mercury thermometers.
Before trying either of these methods be sure to wear the proper
eye and hand protection to protect against broken glass.
method suggested by manufacturers uses a centrifuge. The centrifuge
has to be large enough to ensure that the liquid column will be
forced down. If the cup is not deep enough the column will split,
forcing part of the liquid down. The remainder of the liquid will
be forced up into the expansion chamber, which may break.
Pad the bottom
of the centrifuge cup with soft wadding, such as cotton, and insert
the thermometer, bulb side down, into the cup. Turn on the centrifuge
for a few seconds and the liquid will be forced passed the air gap.
For the second
method, hold the thermometer in an upright position. Gently tap
on the stem above the separation against the palm of your hand.
Be careful! If the thermometer is hit too hard it may break and
could cut your hand. As the thermometer is tapped the liquid above
the separation will break away from the wall and run down to join
the main column.
immersion/partial immersion thermometers - what's the difference?
thermometers are designed to have the bulb and the liquid column
exposed to the temperature being measured. For example, when the
thermometer is used in a water bath set to 80 o C, the entire thermometer
is immersed to the 80 o line and it is pulled out less than an inch
to take a reading. A correction factor may be applied to a total
immersion thermometer used in partial immersion applications.
thermometers are designed to have a specific portion of the thermometer
exposed to the temperature being measured. The amount of immersion
is usually indicated by a ring on the stem or by an inscription
on the reverse giving the depth of immersion.
thermometers may have "total immersion" inscribed on the
back but often they do not. If the thermometer does not say partial
immersion or have a ring around the bottom assume that it is a total
- what do I need?
are calibrated but not all are certified.
When a thermometer
is manufactured it is calibrated against a reference standard. This
is done to correctly identify the scale.
If a thermometer
is certified it means that the manufactured thermometer is measured
a second time against a reference standard at specific points on
the scale. The results are sent from the manufacturer as a calibration
certificate and accompanies the certified thermometer when it is
purchased. These thermometers will need to be re-calibrated periodically
for certain programs such as those administered by the FDA, EPA,
some state agencies and for ISO 9000 compliance.
thermometer that is calibrated with an ice point in its scale requires
only one complete certification in its lifetime. The re-calibration
of the ice point will provide a reliable means for the accurate
adjustment of the remainder of the scale.
Pricing for Non-Mercury Thermometers
We have obtained
special pricing for non-mercury thermometers through Fisher Scientific.
Fisher supplies the Ever-safe thermometers, which have been used
successfully in other replacement programs.
pricing is available through University Stores. To obtain the special
pricing complete a university non-stock order form and submit it
to University Stores.
has two thermometers in stock: