If Dr. K. Guerman himself does not know the answer to this clumzy question nobody in this world would be able

Hi Konstantin,

I don't think the answer to this question is known for certain. My guess is that it is due to autoionization: 2 HTcO4 = TcO4- + TcO3+ + H2O or 2 HTcO4 = TcO4- + H2TcO4+.

This is analogous to the behavior of HNO3 at high concentration: 2 HNO3 = NO3- + NO2+ + H2O

Either TcO3+ or H2TcO4+ could be colored, or they might be strong enough oxidizers to get reduced to Tc(VI), which would disproportionate to Tc(VII) and Tc(V). The reduction potential for the protonated form of HTcO4 is unknown.

Wayne

Hi, Wayne ,

Thank you for your note! It is really very close to the real reason, I suppose.

I noted that HTcO4 is being died differently depending is it dried in an excecator filled with P4O10,  Mg(ClO4)2 or with H2SO4conc. I SUPPOSE THAT some reducing agent participate in the conversion to the red substance. That could be some dust or gas impuriry. It is strange anyhow that the substance could be investigated by solid NMR-Tc-99 wirh very strange spectrum (reported at ISTR-2011).

Is it possible that aggregates or intermolecular interactions in concentrate water solutions or solid state respectively will be responsible of this behavior? The Uv-V spectrum in each case could help us in this way? I think that perhaps it could be possible that the response will be in the relationship of color with the structure in solution (concentrate and diluted-weak or no so weak interactions) and solid state.

To my mind the difference in spectra is too high to be due only to outer sphere effects.

More probable it is due to red-ox behavior

Thanks a lot for the answer.