12-12-2022-2035 - Chelating Agents Continued Various Draft

https://en.wikipedia.org/wiki/Glyphosate 

https://en.wikipedia.org/wiki/1,1,1-Tris(diphenylphosphinomethyl)ethane 

https://en.wikipedia.org/wiki/Tributyl_phosphate 

https://en.wikipedia.org/wiki/Thioglycolic_acid 

https://en.wikipedia.org/wiki/Dimercaprol 

https://en.wikipedia.org/wiki/2,3-Dimercapto-1-propanesulfonic_acid 

https://en.wikipedia.org/wiki/Bis(diphenylphosphinoethyl)phenylphosphine 

https://en.wikipedia.org/wiki/BiPhePhos https://en.wikipedia.org/wiki/Malic_acid 

https://en.wikipedia.org/wiki/ATMP 

https://en.wikipedia.org/wiki/Category:Chelating_agents https://en.wikipedia.org/wiki/Thia-crown_ether 

Structure of the silver complex of a thiacrown ether [Ag(18-ane-S6)]²⁺.

https://en.wikipedia.org/wiki/Thia-crown_ether

https://en.wikipedia.org/wiki/Category:Sulfur_heterocycles

Physical origins

Marble is a rock resulting from metamorphism of sedimentary carbonate rocks, most commonly limestone or dolomite (rock). Metamorphism causes variable recrystallization of the original carbonate mineral grains. The resulting marble rock is typically composed of an interlocking mosaic of carbonate crystals. Primary sedimentary textures and structures of the original carbonate rock (protolith) have typically been modified or destroyed.

Pure white marble is the result of metamorphism of a very pure (silicate-poor) limestone or dolomite protolith. The characteristic swirls and veins of many colored marble varieties are usually due to various mineral impurities such as clay, silt, sand, iron oxides, or chert which were originally present as grains or layers in the limestone. Green coloration is often due to serpentine resulting from originally magnesium-rich limestone or dolomite with silica impurities. These various impurities have been mobilized and recrystallized by the intense pressure and heat of the metamorphism. 

Degradation by acids

Acids damage marble, because the calcium carbonate in marble reacts with them, releasing carbon dioxide (technically speaking, carbonic acid, but that decomposes quickly to CO₂ and H₂O) and other soluble salts :^[19]

CaCO₃(s) + 2H⁺(aq) → Ca²⁺(aq) + CO₂(g) + H₂O (l)

Thus, vinegar or other acidic solutions should never be used on marble. Likewise, outdoor marble statues, gravestones, or other marble structures are damaged by acid rain whether by carbonation, sulfation or the formation of "black-crust" (accumulation of calcium sulphate, nitrates and carbon particles).^[19]

Crystallization

Crystallization refers to a sometimes controversial method of imparting a glossy more durable finish on to a marble floor (CaCO₃). It involves polishing the surface with an acidic solution and a steel wool pad on a flooring machine. The chemical reaction below shows a typical process using magnesium fluorosilicate (MgSiF₆) and hydrochloric acid (HCl) taking place.

CaCO₃(s) + MgSiF₆(l) + 2HCl (l) → MgCl₂(s) + CaSiF₆(s) + CO₂(g) + H₂O(l)

The resulting calcium hexafluorosilicate (CaSiF₆) is bonded to the surface of the marble. This is harder, more glossy and stain resistant compared to the original surface.

The other often used method of finishing marble is the use of polishing with oxalic acid (H₂C₂O₄), an organic acid. The resulting reaction is as follows.

CaCO₃(s) + H₂C₂O₄(l) → CaC₂O₄(s) + CO₂(g) + H₂O(l)

In this case the calcium oxalate (CaC₂O₄) formed in the reaction is washed away with the slurry leaving a surface that has not been chemically changed.^[20]

Microbial degradation

The haloalkaliphilic methylotrophic bacterium Methylophaga murata was isolated from deteriorating marble in the Kremlin.^[21] Bacterial and fungal degradation was detected in four samples of marble from Milan Cathedral; black Cladosporium attacked dried acrylic resin^[22] using melanin.^[23]

 

https://en.wikipedia.org/wiki/Marble