An "absolute" value for the molar volume of Si in Si single crystals is pre
sented as 12.058 820 7(54) cm(3) mol(-1) with a relative standard uncertain
ty of 4.5 .10(-7). It is argued that the consistency of most of the molar v
olume determinations is useful for evaluating the quality of the Si single
crystals involved. A value for the Avogadro constant is derived as 6.022 13
3 9(27) 10(23) mol(-1) having a relative standard uncertainty of 4.6 10(-1)
.