Comparison of the structure of complex compounds in solutions of sulfates of 3d elements of various compositions using the spectrometric method with octahedral complex chromium (III) ions

Abstract

The leather industry collects, processes and turns meat production waste (skins) into  a valuable, unique material - genuine leather (according to the World Leather publication, the annual  meat market produces up to 7.7 million tons of waste in the form of animal skins). Among the mineral  tanning agents, tanning with basic salts of chromium sulfate has been recognized as the best so far, since  chrome-tanned leathers are of high quality. Tanning takes place in an aqueous medium in the presence  of a large number of organic compounds, such as amino acids, products of collagen hydrolysis,  which makes up the skin tissue. The tanned semi-finished product after tanning with chromium (III) salts,  due to the formation of strong chemical bonds with polypeptide chains of collagen, can withstand boiling  for three minutes with shrinkage of the tissue sample of no more than 5%. Metal salts of 3d elements  found in the solution after tanning can be useful in tanning the drumstick and obtaining a tanned  semi-finished product. In this regard, solutions of ferrous (III), chromium (III), cobalt (II), nickel (II),  copper (II) and zinc (II) sulfates were selected for the study. Of particular interest is the structure of the  structure of complex compounds of sulfates of 3d elements and their difference or correspondence to  the structure of tanning complex ions of chromium (III). The structure of complex ions can be judged  by the color of the solutions, by the change in the pH of the medium in which the hydrolysis of salts  takes place, as well as in the presence of amino acids or alkaline agents. Based on the comparative  analysis of colored solutions of sulfates of 3d elements by the spectrophotometric method with a solution  of chromium (III) sulfate, it follows that these compounds, like the complex chromium (III) ion, have  an octahedral form that is not disturbed when interacting with protein amino acids.