A thermometer is an instrument that measures the temperature of any solid, liquid or gaseous matter. It has varied applications in homes, hospitals, science laboratories, restaurants and industrial processes for different purposes such as measuring the temperature of the human body, food, chemical reactions, air leaks, indoors/outdoors, etc.
The most common type of thermometer is made of glass to see the temperature clearly. It has a bulb with a long capillary tube to hold liquid. This liquid is usually mercury or alcohol. Based on what liquid is filled, you can identify it like mercury and alcohol thermometer.
Let’s understand the difference between alcohol and mercury thermometers so that you can put them to the right use and measure the temperature accurately.
Properties of Mercury Thermometer
- It is clearly visible with light silvery colour.
- The temperature range that it can measure falls between -37 degree Celsius (low freezing point) and 356 degree Celsius (high boiling point).
Advantages and Disadvantages of Mercury Thermometers
- It is a good conductor of heat and hence, can measure even high temperatures.
- It gives results quickly – has a fast response time.
- It expands linearly and less than alcohol and any other liquid.
- It is more durable than alcohol thermometer because mercury does not evaporate easily.
- It is smaller in size as compared to alcohol one.
- Mercury does not wet the wall of the thermometer, which means that results can be highly accurate.
- It is highly toxic for living beings and the environment if the bulb breaks and mercury leaks out.
- Mercury is difficult to clean, and it can contaminate the surface on which it leaked.
- It cannot measure cold temperatures.
- It has low thermal co-efficient.
Properties of Alcohol Thermometer
- Since alcohol is colourless, it is dyed, which gives it a bright colour.
- It generally ethanol, toluene, kerosene or other liquid, depending on the manufacturers and range of temperature required.
- The temperature range it can measure falls between -112 degree Celsius (low freezing temperature) and 78 degree Celsius (high boiling point).
Alcohol Thermometer Advantages and Disadvantages
- It is suitable to measure low temperatures because of its freezing point is low.
- It is less toxic than mercury thermometer and hence high on safety factor for human and environment.
- It has a greater value of temperature coefficient of expansion than a mercury thermometer.
- It is less expensive than a mercury thermometer.
- It is less durable because alcohol evaporates faster than mercury.
- It cannot measure high temperature because of a low boiling point.
- It wets the walls of the thermometer, which can adversely impact the accuracy of readings.
Which is Better – Mercury or Alcohol Thermometer?
Well, both mercury and alcohol thermometer have their own merits and demerits. So, it would be unfair to term one better than another. It really depends on the purpose or application for which you want to use the thermometer. Just make sure that you buy a quality thermometer and that too, from a reputed brand or supplier.