<prompt> Orthotoluidine Arsenite test determinesFree residual chlorineCombined chlorineFree and combined chlorine separatelyFree and combined chlorine together  <response>: Orthotolidine -Aresenite OTA TestThis is a modification of the OT test to determine the free and combined chlorine residual separately.Further, the errors caused by the presence of interfering substances such as nittrine, iron and manganese all of which produce a yellow colour with orthotolidine, are overcome by the OTA test.Also knowQuickest and simplest method for free residual chlorine Diethyl parpaphenylene Diamine DPD indicator test.Free residual chlorine is a measure of the portability of water. 