When the pH of the fixer solution is below 3.5, formation of {TAIL ~ hydrogen sulfide gas} can be {HEAD ~ a problem} 
When the pH of the fixer solution is below 3.5 , formation of { TAIL ~ hydrogen sulfide gas } can be { HEAD ~ a problem }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD