A learning value for correcting a basic injection pulse such that an actual air-fuel ratio approximates to a target air-fuel ratio is calculated individually for each injection time number, which is decided according to an operation state of an engine. The chemical reservoir includes one or more channels extending along the inside of the reservoir. The snag resistant opening has a unique shape which reduces the likelihood that the irregular material on the conveyor system will become jammed at the sensor opening or that the edges of the sensor opening will cause damage to the irregular material, or that the sensor opening will become blocked by snagged material. The ferrous and austenitic alloys are particularly formulated for use in oilfield operations, especially sour oil and gas wells and reservoirs. The separating agent is obtained through anionic polymerization of a novel maleimide and serves to separate optically active compounds. When the pusher 4 is pressed in the tip end direction, a tip end face 66 of the stopper 5 comes into contact with a base end portion 28 of the outer tube 2, whereby the depth of insertion of the pusher 4 into the outer tube 2 is restricted, and a set amount of a chemical 100 is discharged through a diameter-reduced portion 22.