Calx

An overview of calx in historical and chemical contexts

For the modern chemical term for calx, see Calcium oxide.

Calx is a term historically used to describe the powdery residue left after a metal or mineral has been subjected to calcination, a process involving heating to high temperatures in the presence of air or oxygen. This term is derived from the Latin word for "lime" (calx), reflecting its early association with lime production.

Historical Context

In ancient and medieval times, the concept of calx was central to the alchemical understanding of the transformation of substances. Alchemists believed that metals were composed of a pure substance that could be extracted through calcination, leaving behind the calx as an impure residue. This process was thought to purify the metal and was a step in the pursuit of the philosopher's stone.

The term "calx" was also used in the context of medicine and pharmacy, where it referred to the ashes or residues of burned substances used in various remedies and treatments.

Chemical Understanding

In modern chemistry, the term "calx" is largely obsolete, having been replaced by more specific terms such as oxide or ash. However, the concept remains relevant in understanding the historical development of chemical processes and terminology.

One of the most common examples of calx is calcium oxide (CaO), also known as quicklime, which is produced by the calcination of limestone (calcium carbonate, CaCO₃). This process involves heating limestone to a temperature of about 900°C, at which point it decomposes into calcium oxide and carbon dioxide (CO₂).

Applications

Calcium oxide, historically referred to as calx, has numerous applications in modern industry, including:

• As a key ingredient in the manufacture of cement and concrete.
• In the production of steel, where it serves as a flux to remove impurities.
• In environmental applications, such as the treatment of wastewater and flue gases.

Also see

• Calcination
• Calcium oxide
• Alchemical processes
• History of chemistry

References

• E.J.,

 Alchemy, 
  
 Dover Publications, 
 1957, 
  
  
 ISBN 978-0486201299,

• Partington, J.R.,

 The Early History of Chemistry, 
 Nature, 
 1935,
 Vol. 135(Issue: 3415),
 pp. 1015–1016,
 DOI: 10.1038/1351015a0,