This research study the effect of the proportion of the media (water - alcohol ) to determine where the arsenic used alcohol ( methanol _ ethanol _ propanol ) Using a Potentiometric method. It conducted the calibration process for the specific size of the solution studied a specific size of the standard solution of iodine Using a Potentiometric method , after the application of analytical conditions and technical optimal to determine arsenic , and then we studied the effect of mixing ratio on the detection limit for arsenic in mixed media (water _ Alcohol ) . The study showed that the value of the detection limit of arsenic vary with the type of alcohol used and accounted for in the reaction medium , it reached to (1× 10-7 M) in media (75:25 water _ methanol ) , but when you use a media ( 75:25 water _ ethanol ) arrived to the limit of detection (1×10-4 M ), As for propanol arrived to the limit of detection (1×10-3 M). where the value reached detection limit of arsenic to (1× 10-5 M) in media ( 50:50 water _ methanol ) , but when you use a media ( 50:50 water _ ethanol ) arrived to the limit of detection (1×10-3 M ), As for propanol arrived to the limit of detection (1×10-2 M). The study showed that the use of the ratio ( 75:25 water _ alcohol ) gave a higher value limit of detection and therefore better results . Was calculated as the standard deviation and standard deviation percentile confidence limit in addition to the feedback that indicates the efficiency of the method of determining the concentration of arsenic detection limit for each medium.