Magnesium sulfate / potassium sulfate / sodium sulfate
"Took the prep @ 5:30pm. Taste not bad... but definitely use the lemon slices. Then did 16 ounces of Gatorade followed by 16 ounces of water.  Make yourself Comfy on the toilet.... I've been here the last 2 hours. It comes on quickly so I wouldn't risk it.... unless you wanna be poopy pants too. Overall, not bad at all. Easy prep"