There are also carbonating alkali calcium compounds (lime, quicklime, etc.) The finished product always needs to be neutralized, and bad actors will skip this step. Lime/chalk, is also used as a cutting agent due to it being within the ideal pH range.
Using chlorinated cracking agents, such as laundry detergent, is dangerous for many reasons, but bad actors do this as well. Combine these two and you've got poison on the streets. This is exactly why prohibition should be replaced with strict regulation.