Copper chloride, commonly called cuprous chloride, is the lower chloride

Chloride

The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

 of copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

, with the formula CuCl. The substance is a white solid sparingly soluble in water, but very soluble in concentrated hydrochloric acid. Impure samples appear green due to the presence of copper(II) chloride

Copper(II) chloride

Copper chloride is the chemical compound with the formula CuCl2. This is a light brown solid, which slowly absorbs moisture to form a blue-green dihydrate. The copper chlorides are some of the most common copper compounds, after copper sulfate....

.
Copper(I) chloride was first prepared by Robert Boyle

Robert Boyle

Robert Boyle FRS was a 17th century natural philosopher, chemist, physicist, and inventor, also noted for his writings in theology. He has been variously described as English, Irish, or Anglo-Irish, his father having come to Ireland from England during the time of the English plantations of...

 in the mid-seventeenth century from mercury(II) chloride

Mercury(II) chloride

Mercury chloride or mercuric chloride , is the chemical compound with the formula HgCl2. This white crystalline solid is a laboratory reagent and a molecular compound. It is no longer used for medicinal purposes Mercury(II) chloride or mercuric chloride (formerly corrosive sublimate), is the...

 ("Venetian sublimate") and copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 metal:

HgCl₂ + 2 Cu → 2 CuCl + Hg

In 1799, J.L. Proust

Joseph Proust

Joseph Louis Proust was a French chemist.-Life:Joseph L. Proust was born on September 26, 1754 in Angers, France. His father served as an apothecary in Angers. Joseph studied chemistry in his father’s shop and later came to Paris where he gained the appointment of apothecary in chief to the...

 characterized the two different chlorides of copper.