carbonnanotube

Last time I used sulpherous acid it was pretty apparent from the smell what it was. That being said you could always measurethe ORP if you have the equipment. The test weimming suggested will also work if you have sample to sacrifice. As a side note that was a fun project. We were trying to take "Red Mud" which is tailing from the bayer process and extract the REEs. Their idea was to use scrubber water from a near by coal plant to do the extraction. It did not work particularly well.