A sheet feeding apparatus includes a stacker for stacking a sheet; a sheet separating device for sequentially separating and feeding the sheet stacked on the stacker; a sheet transport guide for guiding the sheet from the separating device to a processing position; and an ultrasonic wave sensor arranged between the separating device and the processing position for detecting the sheet. In a first reaction zone, 1,3-butadiene is reacted with hydrogen cyanide in the presence of a catalyst to produce pentenenitriles comprising 3-pentenenitrile and 2-methyl-3-butenenitrile. Each of the rows is addressable by a row address. Furthermore, the parameters of the low frequency are changed according to changes of the operating voltage of the discharge lamp. The concave rib is extends about the perimeter of the plunger and extends towards the first end of the plunger. R1, R2, R3 R4 and R5 have meanings given in the description.