You are correct about the sodium chloride in Natron. However... I have also seen references to sodium chlorite and sodium chlorate in archeological resources. Nevertheless... so as not to continue losing the forest for the trees... again... the point that I was making is that there is really nothing new about the use of these sorts of chemicals. This point is also made in the very beginning of the Conclusion of the article:
A Brief History Of Heat And Chemical Preservation And Disinfection - Hugo*...
*Was previously available for free online reading prior to the merger of Blackell Synergy and Wiley. Sorry I didn't make a copy... perhaps someone here has access. Might also be available in this book...