The result was positive, because the S. aureus and E.coli grow around the filter paper, so the measure inhibition zone for each compound of sliver with different concentration is zero. As a result, it means that 1PPM of each compound of silver does not work for killing bacteria.A small piece of 7ppm silver has been collected from the Department of Chemistry. Cut it into 4 small pieces and prepare plates and spread 50μl on E.coli and S.aureus and put each small piece in one plate and incubate for 24 hours at 37C.There should be WII, WIII, WIV, WV and WVII there. WVII is an equivalent of WI only done on a different date and should have the same starting concentration WI. There were no sufficient WI stocks left to concentrate so exchangedit for WVII.Try doing the filter paper experiment again with higher concentrations of silver: try using the highest concentration for all 5 silver solutions: 20ppm, 10ppm, 5ppm. only makeup 2ml of the solution to immerse filter paper in. So, the solutions stretch further. From the solutions, you put your filter papers in, the filters won’t absorb it all, take 50μl and spread it on a plate, let it dry and then spread E. coli and S.