Effect of aqua regia on P, S, C and Si?

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Discussion Overview

The discussion revolves around the effects of aqua regia on a sample containing phosphorus (P), sulfur (S), carbon (C), silicon (Si), and several metals. Participants explore the implications of using aqua regia for dissolving metals while considering the potential reactions and transformations of the non-metallic components in the sample.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • The original poster (OP) questions whether aqua regia will affect the non-metallic components (P, S, C, Si) in their sample while dissolving the metals.
  • One participant asks for clarification on the forms of P, S, C, and Si present in the sample, suggesting that their chemical state could influence the outcome.
  • Another participant suggests that the OP's sample may be an alloy and notes that atomic absorption spectroscopy (AAS) could provide concentrations for non-metallic components as well.
  • The OP clarifies that the sample is a powder and that the non-metals are in their elemental form, expressing uncertainty about the detection of non-metallic compounds using AAS.
  • One participant explains that treatment with aqua regia typically involves boiling the sample, leading to the oxidation of P to orthophosphate, S to sulfate (after passing through sulfite), and the loss of carbon as CO2, while silica remains intact.
  • Another participant reiterates the previous point about the effects of aqua regia on Si, noting that it would also be converted to silica.

Areas of Agreement / Disagreement

Participants express differing views on the effects of aqua regia on the non-metallic components, with some agreeing on the expected transformations while others raise questions about the specific forms of these elements and their behavior during the treatment.

Contextual Notes

There are unresolved questions regarding the specific chemical forms of P, S, C, and Si in the sample, as well as the implications of these forms on the analysis methods. The discussion does not reach a consensus on the outcomes of using aqua regia on the non-metallic components.

allistair
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I've got a sample containing 8 substances: P, S, C and Si (+4 metals) which i need to analyse. I was planning on using aqua regia to dissolve the metals, remove the 4 substances that aren't metals (and deal with them later ^^) and then use atomic absorption spectroscopy to measure the metals' levels but I was wondering if the royal water would have any effect on any of the P, S, C or Si that are also in the sample?

At first glance I would say it would have no effect, but I've never worked with agua regia before and it seems to be a rather peculiar mixture :). Anyone have any experience with this?
 
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allistair said:
I was wondering if the royal water would have any effect on any of the P, S, C or Si that are also in the sample?

In what form are these? Are you actually given red/white/black phosphorus? Is it a phosphate? Is it part of something organic?
Is this part of a powder, or is the sample a solution with sediment on the bottom?
 
The OP's sample may just be an alloy. AAS will give you concentrations for non-metallic components too.
 
The sample is a powder and the P, S, Si and C are present in their 'elemental form' (not sure about the english word... but I mean that they're not bonded with another element).

I also have some rough amounts btw:

Si: 0 < x < 1g
S: 0 < x < 0.1g
P: 0 < x < 0.1g
Mn: 0 < x < 1g
Ni: 0 < x < 0.1g
Cr: 0 < x < 1g
Cu: 0 < x < 1g
C: 1-2% of total sample

But i should be able to detect the non-metallic compounds as well? I thought this technique only worked for metals in solution. I was assuming the non-metallic compounds wouldn't dissolve either.
 
Last edited:
Usually treatment with aqua regia involves boiling the sample to near dryness. Nothing but the silica should resist that treatment. The P will be oxidized to orthophosphate. The S will be oxidized to sulfate (if it isn't already sulfate) but not before it is oxidized to sulfite (which is volatile and will be lost). Carbon will be lost as CO2. Silica will remain in solid form. To analyze the non-metals (perhaps with the exception of P), you will need to withold some of the original sample and analyze it by different methods.
 
thank you for your assistence, much appreciated :)
 
chemisttree said:
Usually treatment with aqua regia involves boiling the sample to near dryness. Nothing but the silica should resist that treatment. The P will be oxidized to orthophosphate. The S will be oxidized to sulfate (if it isn't already sulfate) but not before it is oxidized to sulfite (which is volatile and will be lost). Carbon will be lost as CO2. Silica will remain in solid form. To analyze the non-metals (perhaps with the exception of P), you will need to withold some of the original sample and analyze it by different methods.

Exactly; the OP was talking also about Silicium and that's attacked too (and forms silica).
 

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