Capillary Tube, A Great Little Invention

The scientific area, especially the laboratory practices are really extensive and very varied. As many objects of study as methods and procedures to be employed can be highly alternable. It is for this reason that there is a high diversity of laboratory materials, since each one is adapted to a specific need. The capillary tube has been the little great invention of laboratory materials. Discover how versatile the capillary tube can be and why it occupies the 23rd place in the ranking.

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What is a laboratory capillary tube?

It is known as capillary to a tube of reduced length and diameter of a very small size. It receives this name because due to its characteristic small diameter favors or demonstrates the effect of capillarity. Which is no more that the ascension of a liquid through a thin tube by the cohesive forces and adhesion with the surface.

capillary tube

Other theories reflect that his name comes from of the similarity it possesses with the diameter or thickness of a hair. They can they are made of different materials such as: copper, alloys metal and the most common glass.

Features of capillary tube laboratory

Made of various materials according with its use.They are a fairly narrow circular section.It has about one (1) millimeter in diameter.It conducts fluid inside it by capilaridad.Su name is associated with the resemblance to the thickness of hair.The laboratory capillary tube its diameter measures between 0.5mm to 3mm, while the cooling capillary tube ranges from 1cm to 6cm.

What is the laboratory capillary tube for?

In experimental laboratories, the laboratory capillary tube is used to measure the temperature at which a substance melts. That is, the melting point. In other types of laboratories such as the clinical laboratory, the capillary tube is used for hematocrit measurement. Which refers to the measurement of the globular bundle that is separated from the whole blood through centrifugation. In chemical laboratories it is used to demonstrate the properties of capillarity.

Capillarity - What is it?

Capillarity is a property of fluids that depends of its surface tension. This tension depends, in turn, on the cohesion of the fluid, which gives it the ability to go up or down a tube capillary. In short, it is the ability of a liquid to move through a small tube. What can happen in horizontal and even vertical direction, even against gravity.

This property or action is generated due to the relationship of the forces between molecules of both the surface and the liquid.

Forces involved in capillarity

Capillarity although it is known as a simple event, in reality includes a number of forces that allow this to be possible. Go on in they have:


It is the one that allows the molecules of some liquid to stick to walls of a capillary tube.


It is the property that allows the molecules of that liquid to hold together or adhere to any other substance.

Surface tension

It is the one that allows to keep the surface intact and the formation of the concave or convex meniscus. Which are formed depending depending on whether the cohesion is greater than the adhesion, the menisci are convex.
If it is the opposite case where the adhesion is greater than the cohesion the meniscus it will turn out concave.

Advantages of using laboratory capillary tube

capillary tube

In many laboratories, capillary tubes are preferred over other expansion equipment due to:

  • They are economical.
  • Easy to manipulate and manejar.
  • No they have moving parts.
  • They are simple without solid or liquid deposits.
  • They are disposable so there is no risk of contamination

The capillary tube, although it looks like a simple laboratory material, is one of the best instruments designed in this field. Its physical basis in the properties of liquids is wonderful, as well as functional. It is for these reasons that it occupies the 23rd place in the ranking of the 30 best laboratory materials.

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