November 1, 2021

The muffle is a furnace used in the laboratory . This oven is specially designed for laboratory procedures that require this type of uniform exposure to very high temperatures. The first muffles were designed in France in the 18th century although these were intended for use in pottery.

This furnace is designed for calcination, smelting and other processes in the laboratory that require the use of a furnace. Lighters are often used when heating substances, either to find their boiling point or another procedure, but the use of a muffle responds to other needs.

What is a Muffle?

The muffles are high temperature closed chambers , built with insulating refractory materials. Which means that they resist high temperatures without being affected. This camera is capable of reaching 1700 ° C and has a viewing hole.

It has a door that allows access to the chamber and a top hole to expel gases. When using the muffle, you should only introduce refractory materials as they are the only ones suitable to withstand the high temperatures it reaches.

In this laboratory instrument, the increase in temperature occurs in a regulated and progressive way through its control mechanisms. In the case of electric flasks, they reach a maximum of 1100 ° C, although it will vary depending on the model.

What is a Muffle used for?

The function of the muffle is to reach high temperatures and from there derive all the uses that can be given to it. Reaching between 1100 ° C and 1700 ° C, the flask is the laboratory instrument that reaches the highest temperatures.

Its design allows to have control over the sample entered into the instrument, something very difficult to obtain with other types of furnaces; but very necessary to control the procedure. Although the muffle is certainly not usually used in processes to heat samples with greater control, it is still required to monitor the sample.

The muffle then acts as a furnace but allows you to determine and monitor to a certain extent the conditions of the sample that you are subjecting to high temperatures. In a safe and convenient way.

Uses of the Muffle

The muffles were originally used in pottery for heat treatment, which consists of heating and melting metals and alloys to mold them and improve their qualities such as hardness or elasticity. From there its use spread to other areas until we were given the current laboratory muffle; now in various cases.

One of the most common uses in the laboratory is calcining; Calcination is the process in which you subject an element to high temperatures until it decomposes . This process has many functions, to remove absorbed moisture, carbon dioxide or oxidize the substance. There are also sample analysis processes that are made from the ashes of these.

The muffle is a fundamental part of gravimetric analysis, which consists of determining the elements and proportions in which they make up a sample. This is because one of the steps involves drying and calcining the precipitates, steps carried out using the muffle.

How do you use a flask?

The flask is an instrument that must be used with care to avoid accidents due to working at high temperatures. Once the safety regulations are established, it is easy to use but it is advisable to know the instrument before using it.

One of the things that you must take into account is the necessary temperature to be able to use it; which is an ambient temperature of between 15 ° C to 40 ° C with a relative humidity of 80% but why is this point important?

The answer is that operating the muffle outside of these conditions can hinder its operation, even damaging the apparatus.

The first thing you should do is make sure you comply with the safety measures, such as using the appropriate equipment and leaving the flask at least 15 cm away from other objects so that the heat circulates freely.

Next, check that it is connected to a power source and proceed to introduce the sample. Once this is done you can program the temperature.

Other precautions that must be limited are: do not connect it to a multi-connector or any connection that could overheat. As well as safety measures, such as not staying in front of the muffle while it is operating. Taking these points into account, the rest of its operation is quite simple.

Types of Muffles

The muffles differ in their power source ; in which there are two types, those that work by fuels and the electric ones. This difference affects the temperatures they can reach; being the most powerful fuel muffle, although not the most used.

  • Fuel Muffle

The fuel muffle reaches temperatures of up to 1700 ° C and is used when temperatures of more than 1200 ° C are required. The fuel used is propane gas or natural gas and this connection must be away from the muffle chamber so as not to contaminate the sample. These flasks are mostly used for heat treatment.

  • Electric Muffle

For its part, the electric muffle reaches a maximum of 1100 ° C or 1200 ° C and is the most used in laboratories due to its comfortable size. They are manufactured for 220 VAC networks and have a high electrical consumption; its capacity is less than that of fuel, but normally this does not present disadvantages.

The electric muffle is the preferred one for laboratory use due to its size and there is no danger of contamination of the sample; 1200 ° C is in fact a sufficient temperature for most procedures in which the use of the flask is required. However, the fuel muffle is also used due to its power.

Muffle Features

To become familiar with the flask and fully understand its operation, it is necessary to know the parts that make it up. The muffle requires some maintenance or rather annual calibration, but knowing the proper functioning of its parts will help you determine that it works normally.

  • Inner Chamber : Constructed of aluminum and silica to resist high temperatures. The upper part of the chamber has a hole to expel gases or insert a thermometer to check the temperature.
  • Heating elements : they are inside the chamber, their function is to evenly distribute the temperature.
  • Thermocouple : Sensor that indicates the temperature at which the chamber is located.
  • Timer : It is used to program the working time in which the muffle will operate.
  • Temperature control : This is usually of the PID type to avoid temperature peaks, it is used to program the temperature in the operating muffle. Analog controls have a wider margin of error.
  • Safety switch : This is located on the door that gives access to the chamber; It works by cutting off the power supply to decrease the temperature.

As you can see, the flask itself has two parts, the body and its structure that contains the chamber where the sample is introduced and its control system; where are all the operational controls to program and operate the muffle.

Importance of the Muffle

There are many laboratory procedures that require the application of high temperatures; even more so, being able to apply it in a homogeneous and controlled way to ensure the results of the procedure. Performing this procedure in another type of oven could expose the sample to contamination .

Not to mention that it would imply a greater security risk than the sample is dealing with. The muffle thus becomes the ideal instrument to work at high temperatures with samples in the laboratory, reducing the risk for the performer without compromising its efficiency or operation.

Dr. Loony Davis5
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Born and raised in Brussels in an English family, I have always lived in a multicultural environment. After several work experiences in marketing and communication, I came to Smart Water Magazine, which I describe as the most exciting challenge of my career.
I am a person with great restlessness and curiosity to learn, discover what I do not know, as well as reinvent myself daily, someone who is curious about life and wants to know. I enjoy sharing knowledge.
This is my personal project but I also collaborate in other blogs, it is the case, the most important web on water currently exists in the US, if you are interested you can read my articles here.

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