The Eco-celli Barometer--the first and only liquid mercury-free barometer

History In the seventeenth century the Italian scientist Evangilista Toricelli (1608-1647) was looking for a way to prove that air had weight. In 1643 he proposed an experiment which demonstrated that atmospheric pressure determines the height to which a fluid will rise in a tube inverted over the same liquid. He used a glass tube enclosed at one side and filled completely with mercury. He locked the tube on the open side with his thumb and turned the tube upside down creating a mercury-filled reservoir. When he released his thumb he noticed that a certain amount of mercury remained in the tube. The air pressure on the surface of the mercury in the reservoir pushed the mercury column up and down in the tube. His other observation was that when the column of mercury went down, the weather went bad, and when the mercury climbed up in the tube, the weather changed to fair. His experiment essentially created a sustained vacuum and led to the birth of the first actual and reliable weather instrument.

Hazards The barometer has changed very little since 1643 and if not for the relatively recent discovery that mercury is a very hazardous substance, we would happily continue using Torricelli's barometer. Since it was first isolated, mankind has developed an increasingly vast array of uses for mercury. The Torricelli mercury barometer would be in use for three centuries before the US EPA rated mercury as the 20th most hazardous element. As recently as a few decades ago many of us can recall the intrigue of playing with “quicksilver” from broken thermometers or barometers without realizing its toxicity or that mercury can enter the body through simple skin contact.

The Eco-celli Alternative Less than 10 years ago, Dingens Barometers (www.barometers.com)—one of the world's premier barometer manufacturers—recognized the need for a liquid alternative to the hazardous mercury barometer. They were confronted with a demand from environmentalists who sought a new instrument without mercury but with the similar precision as the Torricelli barometer. The goal was to create an accurate instrument that was environmentally safe. For this project they engaged in the support of Flanders Technology and the University of Diepenbeek. On August 24, 1998 they registered and patented their invention, dubbed the Eco-celli. This environmentally friendly barometer looks similar to a Torricelli, and has accuracy comparable to a mercury barometer in the atmospheric range but it uses no hazardous material. The Eco-celli consists of a U-shaped glass tube filled with a non-toxic, red silicon-based fluid as well as a gas in the top of the reservoir. This is where the Eco-celli differs completely from the Torricelli as the Eco-celli is based on the compressibility of gasses (Boyle's Law) and not solely on gravity. Along side the barometer tube is a precision thermometer is filled with blue colored methyl alcohol. An increase or decrease in temperature can cause the fluid in the barometer to expand and affect the pressure reading. This is corrected by setting the movable scale, which is attached to both the barometer and thermometer, to the top surface of the blue fluid in the thermometer. Manual calculation adjustments for temperature or gravity are no longer needed. The Eco-celli's scale is four times larger than a standard mercury barometer making it much easier and accurate to take a reading. The barometric pressure can be read by aligning the index attached to the scale with the top of the red fluid level. This also serves to show the pressure trend as it remains in place as the red fluid level changes with the changing air pressure.

Key Benefits: • Mercury-free

• Scale 4x larger than the traditional scale w/ English and metric units

• Easy and safe to transport

Principle:

• Based on the compressibility of gasses (Boyle's Law) and not solely on gravity.

• The red silicon-based fluid and gas filled U-shaped tube is the barometer part of the instrument where air pressure is measured.

• The right-hand precision-thermometer is filled with blue colored methyl-alcohol and measures ambient temperature.

• The error margin of temperature in the air pressure values is corrected by setting the moveable scale to the surface of the blue fluid in the thermometer.

• The air pressure can be read by setting the second index to the red fluid level.

• The amount and direction of changes in air pressure between the previous index setting and the current one result in a reliable forecast.

Measurements

• U-shaped and thermometer tubes: length = 32.3”, width = 1.57”, tube diameter = 0.28”

• Thermometer scale: 0°C - 50°C/32°F - 122°F

• Barometer scale: 28.80” – 31.00”/975 mb-1054 mb (dimensions: 9.85” x 1.57”)

Craftsmanship Each handmade piece of glass has a tension after it has been formed. To remove this tension the Eco-celli's hand-blown glass tubes are placed into an oven and heated to 500° C, then cooled very slowly. This 16 hour process maintains the highest standards for quality glass tubes.

Applications Many schools have been forced to give up their mercury models for safety sake and in most cases have replaced them with digital models which unfortunately eliminate the ability to illustrate the science principle of the atmosphere. The Eco-celli allows students to actually see the affects of atmospheric pressure on the liquid in the barometer. An electronic digital barometer cannot provide this visual reinforcement since all the students see are numbers changing, much like a digital clock. The Eco-celli barometer, which has comparable accuracy as a mercury barometer is now the sensible alternative for all schools. In addition liquid mercury barometers are used in many hospitals and medical labs find the local barometric pressure in order to calibrate medical equipment, especially those used to read blood gases. The growing awareness of the danger of mercury and the potential cost of a mercury spill clean-up has motivated many facilities to look for a suitable replacement barometer - and many now choose the Eco-celli Barometer.