The apparent activation energies and pre-exponential factors for the R
ochow reaction, determined from reaction rate measurements at 280-360
degrees C, strongly change, if contact masses are varied with respect
to promoters, to the copper component's nature and percentage as well
as to the silicon type. With each variation, the activation parameters
consequently follow the same Cremer-Constable relation. The isokineti
c temperature is in the range 330 +/- 20 degrees C, i.e., within the r
egion of the reaction temperatures. This implies that the sequence of
activities of compared contact masses can be reversed by a mere temper
ature variation. This may be a reason of contradictions in the literat
ure on Rochow synthesis.