Does salt age cause Inconsistencies?

[Rhodesholar]

I have heard a lot of fellow reefers complaining that when testing their salt batches they find radical inconsistencies say with PH, Alkalinity, Calcium etc. Supposedly, measurements from bucket to bucket bag to bag vary.

I was wondering if the age of the salt could cause this? Would the buffers/trace elements in the salt over time degrade thus causing the issue, or is this just matter of human or test errors, or do the actual batches of salt when manfactured vary that much?

I am not a chemist so forgive my ignorance on the matter and thank you to anyone who responds.

[bertoni]

If the salt were exposed to moisture and CO2, that might cause problems, I guess. I'm not much of a chemist, although the moderator will be back soon. Otherwise, I wouldn't expect the major components to change.

Batch-to-batch variation can be a problem, and the mixes themselves seem to change from time to time.

[Mike O'Brien]

Yes, moisture can cause insoluble precipitate to form.

[JamesJR]

Mike O'brien is right. It can become difficult to dissolve the salt completely if it has been sitting out and become hardened.
It can also to a slight extent, absorb things from the air but that wouldn't have a huge role once you dissolve it in water which would dillute the contaminants. Other than that I wouldn't worry about it.