The solutes, produced by Carlo Erba, Sigma or Fluka, were of the
highest purity commercially available. The “extremely diluted solutions”
were prepared using, as solvent, a solution of sodium bicarbonate and/or
silicic acid, at low and known concentrations (5·10-5÷1·10-4mol·L-1).
The EDS were prepared and stored in laboratory glass containers treated
with a H2SO4/K2Cr2O7 solution. After that treatment, the containers
were rinsed with twice distilled water, until the electric conductivity of
the rinsing water reached a value of 1.2±0.2 μS cm-1, the same as twice
distilled water.