What Is Xylene Used For?

by Lucy Bell-Young

Xylene is used for various industrial purposes, such as in the manufacture of terephthalic acid and dimethyl terephthalate monomers, where it’s used as a chemical precursor. This is one of its most important uses because these are the monomers responsible for creating polymers for plastics, particularly polyethylene terephthalate (PET) and polyester fabrics.

Xylene is also used as an industrial solvent with applications in the printing, rubber, and leather industries. As a solvent, it can be used as a cleaning agent for steel and electronic components like silicon wafers and integrated circuits. Continue reading to learn more about the uses of xylene and how it works. 

Illustration of xylene molecule

Types Of Xylenes

Xylenes are aromatic hydrocarbons with benzene ring components. These chemicals are colourless, sweet smelling, and are flammable with varying flammability thresholds, depending on the type of isomer.

We touched on it in our last blog post about this chemical, but as a recap xylene is not one chemical but rather a category of related chemicals: isomers, which means they all have the same chemical formula (C6H4(CH3)2) but different molecular structures. Xylenes can either be used as a mixture or as separate substances. The three different isomers are o-Xylene, m-Xylene, and p-Xylene, and you can read more about them here.

What Is Xylene Found In?

French chemist Auguste Cahours was the first person who isolated and named xylene all the way back in 1850, where he discovered it as a constituent of wood tar. However, it took several more decades before this new-found chemical had any practical application.

Today, the industrial demand for xylene is high because of the equally high consumer demand for plastic products and polymer materials. In fact, according to recent research, the global demand for xylene will rise to approximately 63.6 million tons by the latter part of 2023.

In natural conditions, xylene occurs in petroleum and coal tar. Xylenes are also found in small amounts in crude oil, ranging from around 0.5-1%, though the exact amount may vary from one source to another. Some crude oil deposits have higher concentrations of xylenes, and even in refined petroleum products, like gasoline and kerosene, there are traces of xylenes.

On an industrial scale, xylene compounds are produced through the process of catalytic reforming and also through the carbonisation during the manufacture of coke fuel.

What Foods Contain Xylene?

There are more food items than you might think that contain traces of hydrocarbons, including xylenes. When this is the case, it’s usually the result of handling and transportation. For example, fresh food like fruits and vegetables might be exposed to xylenes due to environmental contaminants in the soil, water or air.

Some food items that have been found to contain trace amounts of xylenes and other aromatic hydrocarbons include:

  • Meat products (31 µg/kg)
  • Poultry (33 µg/kg)
  • Eggs (7 µg/kg)
  • Milk (4 µg/kg)
  • Bread (9 µg/kg)
  • Green vegetables (2 µg/kg)
  • Potatoes (9 µg/kg)
  • Nuts (63 µg/kg)
Petroleum pouring out of orange container
In natural conditions, xylene occurs in petroleum and coal tar

What Is The Function Of Xylene In Staining?

One of the most important uses of xylene is in medicine, particularly in histology or the microscopic examination of tissues. Here, it is used in the staining process of tissues for microscopy. In a nutshell, histopathologists can examine tissues for tell-tale signs of any disease. Tissues are prepared using paraffin wax for cutting, and xylene is used because it’s highly miscible with paraffin, making the cell transparent.

Xylene has an essential role to play in this process. Here’s the detailed step-by-step process of staining a tissue sample for microscopic examination if you want all the ins and outs – if not, here’s our brief overview:

Step 1: Fixation

Sample tissue blocks of about one cubic centimetre in dimension, or sometimes whole organs, are chemically treated with a 4% solution of formaldehyde to bind and create cross-links to some proteins in the tissue samples. The proteins are then denatured and dehydrated, which hardens them and deactivates the tissue enzymes that could degrade the cells. Bacteria and fungi are also destroyed in this process.

Step 2: Dehydration and clearing

The tissue sample is gradually dehydrated by washing it in increasing concentrations of ethyl alcohol. Eventually, the water in the cells is replaced by 100% alcohol. The alcohol is then replaced by xylene. This preparation is necessary to allow the tissue sample to be embedded in paraffin wax while maintaining its structure.

Step 3: Embedding

The tissue sample is now immersed in a bath of paraffin. Since paraffin is miscible with the xylene, the melted wax fills the interior of the tissue cells, forming a clear filler. 

Step 4: Sectioning

When the wax hardens, the tissue can then be carefully cut into thin slices using a microtome. Next, the thin sections are stained and placed on a microscope slide for examination.

Step 5: Staining and mounting

This step is basically the reverse of step two. Since most staining agents are water soluble, the paraffin must be removed first. To do this, the sectioned samples are passed through xylene in order to remove the paraffin. The samples then need to be rehydrated, so they’re washed with alcohol at decreasing concentrations, from 100% to 0%, until they are finally washed in water.

When stained, the samples are again dehydrated and placed in xylene. The sections are then mounted on microscope slides in a medium dissolved in xylene. A cover slip is put on top of each sample and the xylene is allowed to dry. Finally, the mounting medium hardens and binds the coverslip on the microscope slide.

Scientific background with modern histopathology tools
One of the most important uses of xylene is in medicine, particularly in histology or the microscopic examination of tissues

What Is Xylene Used For In Painting?

Xylene is commonly used as a paint solvent because it’s excellent at removing old paint on a variety of surfaces. It’s also effective at removing greasy stains, resins, enamels, and glue.

As a paint thinner, this chemical has some advantages over other paint thinning agents like toluene. This is due to the fact that xylene doesn’t evaporate as fast as other paint thinners, meaning that it can be more effective at thinning chunks of paint or lacquer. This allows you to apply paint more evenly on a surface.

Xylene is also the preferred thinner for those who use spray paints because it facilitates a better flow. Even if you use a paint brush or a roller, you can prevent clots or chunks by using xylene as a paint thinner.


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