|
THE ORCBS > Chemical Safety > Programs & Guidelines > REPLACEMENT OF MERCURY THERMOMETERSPublic 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:
If the thermometer use does not meet one of the exemptions, a mercury free alternative will need to be purchased.
Special storage requirements for non-mercury thermometers When stored 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. Selecting equivalent non-mercury thermometers Before purchasing 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. Next, identify the properties of the thermometer that was broken:
Then, identify 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. Finally, identify the alternatives:
Recombining separated non-mercury thermometersManufacturers 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. The preferred 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. Total immersion/partial immersion thermometers - what's the difference?Total immersion 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. Partial immersion 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. Total 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 immersion thermometer. Calibration/Certification - what do I need?All thermometers 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. A certified 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. Special Pricing for Non-Mercury ThermometersWe 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. The special pricing is available through University Stores. To obtain the special pricing complete a university non-stock order form and submit it to University Stores. University Stores has two thermometers in stock:
| ||||||||||||||||||
