Concentrated sulfuric acid turns black. Why?
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This post was last edited by sunjl1981 on 2013-1-6 at 20:01. Our factory uses concentrated sulfuric acid for drying purposes, to dry acetylene and hydrogen chloride; the concentrated sulfuric acid that results is black in color. What could be the reason for this? Has anyone encountered this situation? It is filtered, and black solid particles are present. # hcbbs
It is caused by organic substances in acetylene or hydrogen chloride; please conduct an investigation.
This post was last edited by huawei on 2009-12-31 13:27. One possibility is that it is caused by organic substances carbonized by concentrated sulfuric acid; the analysis above is correct. Another possibility is that it results from the corrosion of steel by sulfuric acid.
Entering organic or inorganic substances will cause carbonization. While cleaning the concentrated sulfuric acid from the chlorine gas pipes, I truly witnessed the power of concentrated sulfuric acid to dehydrate and carbonize materials; it was as if fire were at work, with smoke being produced and heat generated. I touched a piece of cotton fabric that was undergoing carbonization using gloves, and it was hot – perhaps around 50 degrees Celsius. Have anyone else ever seen something catch fire due to concentrated sulfuric acid reacting with materials that are prone to carbonization?
Yes, it’s likely that the sulfuric acid turns black due to the carbonization of organic matter; it is recommended to use white quartz sand for filtration so that the composition of the filtered material can be analyzed. The transparency of the sulfuric acid after filtration should increase.
Agree with the opinion above; the issues of equipment corrosion and impurities
Regarding equipment corrosion, it is taken into account during the design process at normal temperatures; therefore, I believe it’s not corrosion per se, but rather an issue with gaskets in the pipelines, as well as the substances present in the materials. Ferrous sulfate isn’t black, right? Hehe.
There shouldn’t be any issue with organic matter. There is no possibility of organic substances being present in either acetylene or hydrogen chloride. It might be a problem with equipment corrosion.
⑴In the case of sulfuric acid, dehydrating properties are characteristics of concentrated sulfuric acid, not dilute sulfuric acid; that is, concentrated sulfuric acid exhibits strong dehydrating properties. ⑵Dehydration is a chemical property of concentrated sulfuric acid. The process by which substances are dehydrated by concentrated sulfuric acid is a chemical change; during this reaction, concentrated sulfuric acid removes hydrogen and oxygen atoms from the substance being dehydrated in a ratio corresponding to that of water molecules (2:1). ⑶Substances that can be dehydrated by concentrated sulfuric acid are generally organic compounds containing hydrogen and oxygen. Among these, the organic matter in substances such as sucrose, wood chips, paper scraps, and cotton undergoes dehydration to form black carbon (carbonization), while sulfur dioxide is also produced in the process. It may be due to the low purity of the material; the organic substances contained in it react with concentrated sulfuric acid, resulting in carbonization.
At excessively high temperatures, concentrated sulfuric acid and acetylene can also react to form carbon
Concentrated sulfuric acid can also carbonize acetylene