These ring compounds are maintained in a concentration of {HEAD ~ between 0.01 and 4.0 grams} per {TAIL ~ liter} of solution in the bath 
per
These ring compounds are maintained in a concentration of { HEAD ~ between 0.01 and 4.0 grams } per { TAIL ~ liter } of solution in the bath
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH