Zinc Protects!

Discovering the 8th  Metal

A History  of Zinc

 Fathi Habashi

Centuries before   zinc  was discovered   in  the  metallic form,  its  ores   were   used   for making brass and zinccompounds were used for healing wounds and sore eyes.  Although  the word brass frequently occurs in the OldTestament, there is little evidence that an alloy of zinc and copper was known in early times.  The word translated “brass” might equally well be rendered  bronze  or copper, both of which were in common  use.

 In the latter part of the thirteenth century, Marco Polo described the manufacture of zinc oxide in Persia and how thePersians prepared tutia (a solution of zinc vitriol) for healing  sore eyes.

 The Roman  writer Strabo (66 B.C. – 24 A.D.) mentioned  in his writings that only the Cyprian ore contained “thecadmian stones, copper vitriol, and tutty,” that is to say, the constituents from which brass can be made. It is believedthat the Romans first made brass in the time of Augustus  (20 B.C. to 14 A.D.) by heating a mixture of powderedcalamine, charcoal and granules of copper. Roman writers observed that coins made from orichalcum wereundistinguished from gold.

 

 

 

Biringuccio  (ca. 1540) has the next most complete description of brass making. He described how either calamine orfurnace tutty could be mixed with broken up pieces of copper and sprinkled with a layer of powdered  glass, then heatedin a closed crucible for 24 hours.

Agricola (Figure4) in 1546 reported that a white metal was condensed and scraped off the walls of the furnace whenRammelsberg ore was smelted in the Harz Mountains to obtain lead and silver to which he gave the name “contrefey”   because it was used to imitate gold.  This often consisted of metallic zinc, although he did not recognize it as such. Heobserved, furthermore, that a similar metal called “zincum” was being produced  under similar circumstances  in Silesia by the local people. Paracelsus (1493-1541) (Figure 5) was the first European to state clearly that “zincum” was a newmetal and that it had properties distinct from other known metals.

 

 

 

Thus, by about 1600, European scientists were aware of the existence of zinc. All the metal they had examined,however, had likely been imported  from the East by Portuguese, Dutch and Arab traders. However, there  was aprofusion  of names quite unrelated to the local names for zinc ores.  These included tutenag – derived from thePersian tutiya, calamine, which became the English tutty, zinc oxide – and spelter, likely from the similar coloured lead-tin alloy, pewter, or the Dutch equivalent, spiauter or Indian tin which the British scientist Robert Boyle latinised tospeltrum in 1690 from which originates spelter, the commercial term for zinc. The word tutia, an old name for zinc oxide,is derived from a Persian word that means smoke and refers to the fact that zinc oxide is evolved as white smoke whenzinc ores are roasted with charcoal.

 

In Renaissance times, latten (or laten, laton, lattyn) became the common English word for brass, akin to the Frenchlaiton (= brass) and Italian  latta (= sheet brass), and probably  based on the Latin latte or lathe (= sheet).  The origins  ofthe German word for brass, Messing, may be related  to the Latin massa (= lump of metal). The modern  English brassmay be related  to the French braser (= braze or solder). The word “zinc”  may be derived from the Persian word singmeaning stone.  In Arabic, zinc is known as kharseen, i.e. Khar from Al-Ghar = mine, seen from Al-Seen = China,hence kharseen, the metal from Chinese mines. The spelter trade with the East flourished throughout the seventeenthand first half of the eighteenth  centuries, although  there seem to be no records concerning the tonnages involved.

In an extensive  research “On the method of extracting zinc from its true mineral,  calamine”, Andreas Marggraf (Figure6) in 1746 reduced calamine from Poland, England, Breslau and Hungary with carbon in closed retorts and obtainedmetallic zinc from all of them. He described his method in detail, thereby establishing the basic theory of zinc production.Marggraf also showed that the lead ores from Rammelsberg contained zinc and that zinc can be prepared fromsphalerite.  Marggraf  was probably unaware that in 1742, the Swedish chemist  Anton von Swab (1703-1768)  haddistilled zinc from calamine and that, two years later, he had even prepared it from blende. Since the vapors rose to the top of the alembic  before  passing into the receiver,  this process  was called distillation per ascendum. In 1752Swab and another Swedish chemist Axel Fredrik Cronstedt (1722-1765) developed at government  expense the use of Swedish zinc ores for the manufacture of brass,  to avoid the necessity of importing calamine.

 

 

The knowledge  of deliberate zinc smelting in a retort was acquired by an Englishman on a visit to China just prior to 1740.
A vertical retort procedure was developed by William Champion (1709-1789) and by 1743 a zinc smelter had beenestablished at Bristol in the United Kingdom. A charge of calamine and carbon was sealed into a clay crucible having ahole in the bottom. This was luted onto an iron sat in a tub of water and it was here that the metallic  zinc was collected(Figure 7). The distillation took a total of about 70 hours to yield 400 kg of metal from all 6 crucibles positioned in thefurnace. An annual production rate of 200 tons has been suggested for the works at that time.

This  type of apparatus continued  to be employed until 1851 although it was fuel inefficient, consuming 24 tons ofcoal for every ton of spelter produced. In 1758, William’s  brother,  John, patented the calcination of zinc sulfide tooxide for use in the retort process, thereby  laying the foundation for  the commercial  zinc practice which continuedwell into the twentieth century. The English zinc industry  was concentrated  in Bristol and Swansea.The Welsh process was a batch operation which required withdrawing the crucible and retort after each cycle. It waslabour intensive and fuel inefficient. A major technological  improvement came with the development of the German process by Johann Ruberg (1751-1807)  who built the first zinc smelting works in Wessola in Upper Silesia in 1798which used the horizontal retort process developed by him. The principal  advantage of this technique  is that the retortswere fixed horizontally into the furnace allowing them to be charged and discharged without cooling. By placing theretorts in large banks, fuel efficiency was greatly  increased. The raw material  initially used was zinc galmei (calamine), a by-product  of lead and silver production. Later, it became possible to produce zinc directly from smithsonite,  aneasily smelted ore. This was shortly followed  by the use of zinc blende, which had first to be converted into the oxideby roasting. After this development, other smelting works were soon erected in Silesia near the deposits, in the areasaround  Liège in Belgium, in Aachen, in the Rhineland and Ruhr regions in Germany.