According to foreign media reports, chromium is a common alloy additive used in the manufacture of tool steel or stainless steel and other materials. People have always believed that it was invented in the late 19th and early 20th century. A team led by rahil alipour of University College London (UCL) studied several Medieval Persian manuscripts and identified an archaeological site in southern Iran called chahak, which used to be an ancient steel production site. In particular, one of the manuscripts attracted their attention. The manuscript, called al jamahir fi marifah al jawahir, was written by the learned Abu rayhan Biruni in the 10th or 11th century A.D. Crucially, it contains the only known formula for forging steel in high temperature crucibles. “The identification process can be quite lengthy and complex for several reasons,” says Marcos Martinon Torres, a recent author of the study’s paper. First, the language and terminology used to document technical processes or materials may no longer be used, or their meaning and attributes may differ from those used in modern science. In addition, writing is limited to social elites, not to individuals who actually practice this skill, which may lead to errors or omissions in the text. ” < / P > < p > among them, an ingredient called “rusakhtaj” puzzles archaeologists. Eventually, they determined that it was chromite, which could be used to make chromium crucible steel. The discovery of this important trace of chromium in chahak site also supports this view. < / P > < p > the research team determined that this process occurred between the 11th and 12th centuries by dating several pieces of charcoal recovered from the crucible and on-site slag. Scanning electron microscope images showed traces of chromite, and in the crucible slag, they found chromium in steel particles ranging from 1% to 2%. Although this is much less than the chromium found in modern stainless steel and tool steel, which can contain 11% to 13% chromium, the fact that it exists in something so old is of great significance to the scientific community. < / P > < p > the research team said that manuscripts of that era praised the complex shape of chahak steel, but also pointed out that the sword made of this material was brittle. The report shows that the number of app store purchases soared in the first half of this year due to the impact of covid-19