THE SI-28 PATH TO THE AVOGADRO CONSTANT - FIRST EXPERIMENTS AND OUTLOOK

For the first time an attempt has been made to determine the lattice p arameter, density, and molar mass of an isotopically highly enriched s ilicon-28 crystal. The goal was to achieve an independent value of Avo gadro's constant of accuracy equal or superior to current best values obtained from similar measurements of very pure and highly perfect sil icon single crystals of natural isotopic composition. That aim has bee n foiled by unexplained contaminations of the Si-28 crystal and perhap s other unidentified causes. Under these circumstances this paper rest ricts itself to a brief record of the method used and the results obta ined. The value of the Avogadro constant so derived is considered of n o further significance and differs from the CODATA and other credible values by about 1.10(-5)N (A).