The moment you start your professional development in the field of chemistry, you begin to find yourself with a wide variety of tools and measuring instruments. Proper understanding and mastery of these will help you achieve more accurate results, whether you are working with a bulk material or testing hazardous chemicals.
The fact is that it is necessary to know which are the most indispensable tools for any chemist. Among the large number that there are, there are pycnometers, so today’s article will have the opportunity to know what is a pycnometer, how it is used, how it works and many more aspects. Continue reading and learn all about it.
Concept and definition of pycnometer
It is one of the instruments that are usually found in chemical laboratories and that has a measurement use. In this sense, a pycnometer is a way to measure how much density a liquid has experimentally. This applies to a wide variety of substances, making it a perfect instrument for know exactly the density of a liquid.
In general, the pycnometer is used when there is no knowledge of the density of a liquid, be it a solution or an element in its purest state. In fact, this instrument has a double function, the what is to measure the densityas well as the weight of a particular liquid, such as water, honey, oil, prepared solutions, among others.
Regarding the shape or how a pycnometer is, it is made of glass and generally has a relatively small size. It has a beveled lid in which a capillary is located, and, although we said that it is used to find liquid densities, it is also possible apply the same principles for solids.
In fact, it is thanks to its design that it allows the study of the density of a liquid in a properly equipped laboratory. This for the simple reason that it has a kind of conduit through which the air bubbles travel a path until they reach the top and are released. For this reason, this last part or process is fundamental, since the final results depend on thisso they can be more or less exact.
What is the pycnometer method?
Because all pycnometers have pre-set measurements, determining the density of a liquid is much easier, but it can be applied to any solid as well. This is why the measurement and study method used with this instrument is based on the following points:
- it is vital own a measuring scale that allows to know the weight of a liquid.
- The design of these instruments is made so that the gases can complete their journey and then be released through a special stopper.
- Depending on how many bubbles there are, the density and weight of the liquid will be affected.
- It is vital that the person handling the pycnometer perform a calibration every so often.
From here is when it begins to carry out the measurement process. That is, preparing the instrument to be used, cleaning it, calibrating it, weighing it when it is empty, among other things. Regarding the steps to follow in order to use the pycnometer, consider the following:
- Remove the stopper that it has and then pour the liquid to be measured or studied.
- Now you must place the cap that you removed.
- The liquid will go up through internal ducts, everything will depend on whether or not you have this system.
- Once the liquid reaches a certain mark established on the instrument itself, it is when the first measurements can be made.
- It is important to add distilled water to complete this study process.
- The water needs to settle a bit once it is added to the pycnometer.
It is important to note that there are two measurements to be made. The first one is without the water, and the second, already with all the elements in the pycnometer. In case you have wondered what is more accurate when making measurements, having references and several samples gives you a very good approximation of what is real.
What is a pycnometer used for?
We can say that, in a certain way, these measuring instruments are similar to hydrometers. However, the differences can be noticed in terms of their structure or physical design, otherwise they work in the same way. So whether you have a pycnometer or a hydrometer, Can you find the density of a liquid?. Now, the first instrument allows you to know such values based on the weight of a liquid. While, in the second case, the hydrometer bases its operation on the principles of Archimedes.
To do it in a much more summarized and direct way, picometers are used to:
- measure or know the values of density of a liquid.
- They can make it easy to measure the volume of any gas.
- It is possible to apply these principles to the measurement of densities in solids.
An important fact to mention is that they can also be used to measure specific gravity, as well as light refraction and other physical properties that are linked to the nature of liquids, such as temperature, viscosity, impurities, among others. others.
How does a pycnometer work?
If you want to know how a pycnometer is used, you need to know how it works. In general, it is an instrument which is usually calibrated to be able to make measurements of a particular liquid. In fact, what is done in this regard is to compare the values obtained after a measurement with the density of water. In other words, if you want to calculate the density of cooking oil, you measure its density and compare it with the density of water.
You can achieve this thanks to the weight and volume of the liquid. Now, in terms of volume, this value can be obtained using a graduated cylinder or, failing that, a pipette. Regarding the weight, it is enough that you do use of an electronic scale. It is important to note that the vast majority of pycnometers have two bulbs made of glass and have a vacuum between them.
This simple detail helps a lot when it comes to knowing the pressure difference between the bulbs and, thus, being able to determine the density of the liquid to be studied. It is important to note that these instruments have the capacity to be able to make measurements without the need for physical contact. Therefore, you can work with highly toxic or dangerous elements or liquids and still be fine. Sure, as long as you know how pycnometers are used.
What magnitude does the pycnometer measure?
When making measurements with this instrument, magnitudes such as the mass and volume of a liquid must be taken into account. Thanks to this, both the relative density and the absolute density are expressed in the same magnitude: kilogram per cubic meter. However, this can be expressed in other units of measurement thanks to the use of the CGS system. Thus, you can also express the density of a liquid as grams per cubic centimeter.
How is density measured with the pycnometer?
The main thing is to have a reference value, which, in most cases, turns out to be the density of water. Then the density of the liquid to be studied is known and once both data are available, the mass of a reference volume is compared with the mass of the liquid being studied. It is important to consider that not all pycnometers have the same capabilitiesthe smallest can have a maximum capacity of 5 mL, while the largest can exceed 35 mL.
Regarding mathematical studies, you have the following formula to know the density: D = (M1*P1)/Ma. The “D” represents the density to be calculated, “M1” is the mass of the liquid and “P1 and Ma” is given by the density and mass of the water. With all these values, the result you will get It is expressed in grams per cubic centimeter.
What are the characteristics of a pycnometer?
- It is a measuring instrument that can be made of different materials and different capacities.
- Some pycnometers have a sensor that allows them to determine the temperature of a liquid after it has been heated.
- They may be designed with integrated circuits that help facilitate calibration and data logging.
- They can be used for thick liquid matter such as paint or more pasty substances.
Can a pycnometer be heated?
This will largely depend on the type of material the pycnometer is made of. However, this instrument is not recommended or should be heated. The reason for this is because the volume of the material to study tends to increase and change. In the same way, heating a pycnometer implies that there is a kind of oxide, which causes the mass to be studied to be inconsistent.
What is the classification that pycnometers follow? – Guys
Regarding the classification or types of pycnometers that exist, the following are found on the list:
- gas pycnometer: This type of instrument uses gravimetry to study the samples. It is one of the most used in the vast majority of laboratories.
- Gay-Lussac pycnometer: What characterizes this one, in particular, is its great precision with the measurements.
- Chatelier’s pycnometer: Its physical shape resembles that of a volumetric flask, but with more width.
- Stainless steel pycnometers: These are usually used mainly for materials that are highly viscous, such as paints, oils and others.
- Chapman’s pycnometer: its shape makes it unique, since they are designed with two bulbs inside. Its main characteristic is to allow knowing the humidity percentage.