In {HEAD ~ Step} 23, the pumping of {TAIL ~ the solution} and the discharging of the liquid are controlled to optimum rates 
In { HEAD ~ Step } 23 , the pumping of { TAIL ~ the solution } and the discharging of the liquid are controlled to optimum rates
OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH