Given that it is difficult to determine who is telling the truth in the recent claim that J&J covered up finding asbestos in their powder, is there any chemical test that we can perform on our own to determine with reasonable confidence whether the particular sample of powder we have bought contains asbestos? (I am aware that one test involves viewing the sample under a sufficiently high-powered polarizing light microscope, but not everyone has such a tool.)

I have not much chemistry background beyond high-school, and it seems that there are numerous kinds of asbestos, apparently characterized more by their large aspect ratio than by their chemical composition. For example, chrysotile (which accounts for ≈95% of asbestos in buildings in the US) has an idealized chemical formula $\ce{Mg3(Si2O5)(OH)4}$, but may not even occur as exactly that. Talc according to wikipedia is either $\ce{H2Mg3(SiO3)4}$ or $\ce{Mg3Si4O10(OH)2}$. These break down as follows:

Chrysotile: $\ce{(Mg^2+)3[Si2O5]^2−([OH]^−)4}$

Talc A: $\ce{(H+)2(Mg^2+)3([SiO3]^2+)4}$

Talc B: $\ce{(Mg^2+)3[Si4O10]^4−([OH]^−)2}$

So we cannot test for $\ce{Mg^2+}$ or $\ce{[OH]^−}$. But is there a chemical test for $\ce{[Si2O5]^2−}$ that can be done at home? And is it safe to rule out chrysotile if no $\ce{[Si2O5]^2−}$ can be detected, or can the amount be too low for chemical detection but still dangerous?

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    $\begingroup$ The chemical difference between asbestos and talc is very small: the differences are structural. This is why the best test is probably to look at a sample with a microscope. $\endgroup$
    – matt_black
    Dec 31 '18 at 20:29
  • $\begingroup$ @matt_black: Thanks, but I'm not sure I understand your comment. Are you saying that talc has Si2O5 as well? Or are you saying that Si2O5 has very similar chemical properties to Si4O10? Or something else? $\endgroup$
    – user21820
    Jan 1 '19 at 9:07
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    $\begingroup$ @user21820 Very different minerals result from small changes to the structure of the silicate units they contain. The differences are caused by the subtly different way the SiO2 units are connected. Those differences are not easy to detect chemically. So, yes, Si2O5 is hard to tell apart from Si4O10 using chemistry (but trivially easy looking at the crystals of the mineral). $\endgroup$
    – matt_black
    Jan 1 '19 at 11:32
  • $\begingroup$ @matt_black: I see. It's a bit disappointing to be unable to do it myself, since I've read that some talc sources are contaminated while others are not, so I wouldn't simply trust any testing done on samples provided by the company, and one would need to test a statistically significant number of samples from off the shelves to be relatively confident there is no asbestos. As of now, with many involved parties withholding a lot of information, I would've liked to just ignore them and check for myself. $\endgroup$
    – user21820
    Jan 1 '19 at 11:39
  • $\begingroup$ you can do it yourself, build x-ray diffraction apparatus $\endgroup$
    – Adam
    Aug 31 '19 at 15:56

Is there a chemical test for $\ce{[Si2O5]^2−}$ that can be done at home?

First $\ce{[Si2O5]^2−}$ isn't a poly atomic ion like sulfate ($\ce{SO4-}$) or nitrate ($\ce{NO3}$) but represents a stoichiometry in the material.

Unfortunately at this time a test without x-ray diffraction is not possible. Asbestos/chrystolite is not just a chemical formula, but a crystal structure. It's not just what it is made of but also how the atoms are structured that makes it potently carcinogenic. If you were to take asbestos and melt it then cool it sufficiently fast to form a glass (amorphous/non-crystalline substance), it would not have similar carcinogenic properties as the crystalline material.

I am aware that one test involves viewing the sample under a sufficiently high-powered polarizing light microscope, but not everyone has such a tool.

It is worth noting that using polarized can be done at home with polarized filters but is a presumtive test not a direct method. Essentially all chrystolite will rotate light but not all minerals that rotate light are chrystolite.

  • $\begingroup$ Oh thanks very much for your answer. So am I correct to say that it was wrong for me to break down the formula "Mg3(Si2O5)(OH)4" into ionic 'components'? Also, thanks for explaining that the polarization test yields false positives. $\endgroup$
    – user21820
    Mar 22 '19 at 15:57
  • $\begingroup$ @user21820 Yes, but I will note that the bonding of silicates is somewhat an exception compared to other oxide ions (phosphate, borate, sulfate, carbonate, nitrate, chlroate, etc...) so I would say the intuition was good but silicates are a curve-ball. $\endgroup$
    – A.K.
    Mar 22 '19 at 16:13
  • $\begingroup$ I see. I was aware that silicates can be macromolecules, such as SiO2, but I got confused by the metal ions. Based on what you said, I would now guess that you have an Si2O5 macromolecular structure with embedded Mg2+ and OH− ions to balance out the charges. Right? $\endgroup$
    – user21820
    Mar 22 '19 at 16:40
  • $\begingroup$ @user21820 Essentially yes, but the word is network solid not macromolecule. $\endgroup$
    – A.K.
    Mar 22 '19 at 17:00
  • $\begingroup$ Ok thanks, though the article you cite says "In a network solid there are no individual molecules, and the entire crystal or amorphous solid may be considered a macromolecule". Haha.. $\endgroup$
    – user21820
    Mar 22 '19 at 17:02

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