Environmental Project, 1102 – Alternatives to mercury-containing measuring devices – 6 Other mercury-containing measuring devices

Alternatives to mercury-containing measuring devices

6 Other mercury-containing measuring devices

Apart from the devices described in this study, mercury may be used in a number of other measuring devices. The total mercury consumption in Denmark with these other measuring devices before the coming into force of the current ban is considered marginal, and no exemptions for applications on any of these devices have been granted by the Danish EPA. Alternatives to the mercury-containing devices have not been investigated in this study, but they are apparently available on the market.

Coulter counters
Rasmussen (1992) describes at the beginning of the 1990s that mercury may be present in coulter counters, used for automated counting and measuring the size of microscopic particles. They are widely used in the hospital sector. Mercury was in Denmark used in the manometers of the counters. From the U.S.A. it is reported that mercury may be present in a pressure gauge, on-off switch, timing count gauge, vacuum gauge and possibly other gauges, depending on the model (Sustainable Hospitals 2000).

Gas flow meters
Precision flow meters, used for calibration of gas flow meters for small flows, contained (and may still contain) mercury in a friction-less sealing (Rasmussen 1992). The precision flow meters were held by a few institutions calibrating equipment and in total about ten of these meters had been sold in Denmark (Rasmussen 1992).

Hygrometers
From the U.S.A. it is reported that mercury may be used in hygrometers (Gallican et al. 2003). No information on the use of mercury in hygrometers has been reported in Denmark, and it has probably not been used for many years (if ever). A hygrometer is an instrument used to measure the moisture content of air or any gas. The most common type of mercury-containing hygrometer is the "dry and wet bulb psychrometer." The psychrometer is best described as two mercury thermometers, one with a wetted base, and one with a dry base. The water from the wet base evaporates and absorbs heat causing the thermometer reading to drop (Gallican et al. 2003).

Hydrometers
From the U.S.A. it is reported that mercury may be used in hydrometers (Gallican et al. 2003). No information on the use of mercury in hydrometers has been reported in Denmark, and it has probably not been used for many years (if ever). A hydrometer is a device that measures the density or specific gravity of a liquid. Hydrometers are calibrated based upon the specific gravity of water at 60°C being 1,000. Liquids denser than water will have a higher specific gravity, while liquids less dense will have a lower specific gravity. The hydrometer is used for many applications.

Pyrometers
From the U.S.A. it is reported that mercury may be used in pyrometers (Gallican et al. 2003). No information on the use of mercury in hydrometers has been reported in Denmark, and it has probably not been used for many years (if ever). Pyrometers are used to measure the temperature of extremely hot materials, and are used primarily for foundry applications. Infrared thermometers are today marketed for this application area.