Scale samples that cannot be dissolved by aqua regia
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Hello, friends: A sample was brought to me by a colleague, and it needs to have its components analyzed. I tried using HCL and HNO3, but neither of them was able to dissolve it; the same was true when using aqua regia. What kind of scale causes this situation? I heard it’s inside the gasifier. What are the typical ingredients?
It’s difficult to determine; I recommend using microwave digestion for the samples followed by elemental analysis.
1. Melt the solid sodium hydroxide in a nickel crucible and then add acid to dissolve it. 2. Ask in detail about the source of the sample
This post was last edited by qugd on 2010-4-18 at 19:04. Wang water is a strongly oxidizing mixed acid consisting of 3 parts salt and 1 part nitric acid; it can dissolve metals as well as some non-metals with reducing properties. However, it is powerless against some stable non-metallic compounds that do not undergo reduction. The most typical example is that aqua regia can be stored in glass containers; from this, it can be inferred that such scale must be silicate scale. Similarly, aqua regia cannot dissolve corundum, that is, materials similar to agate. Remember one truth: aqua regia cannot dissolve everything; otherwise, what would we use to hold them? This kind of scale can be dissolved with strong alkalis or hydrofluoric acid; go ahead and give it a try after reading my post. If it can’t be dissolved any further, then the issue of scaling will need to be discussed further. The slag in the gasification furnace is likely to be a silicate-based substance.
Silica, right? This stuff isn’t affected by acids
If dissolution doesn’t work, use melting. The flux can be sodium hydroxide or sodium carbonate, among others.