[Finn Berger]

You will get more consistent results measuring by weight than volume

One caveat though: Mineral salts are hygroscopic, and you don't really know how much water they may have absorbed.

Adhering to the KISS principle I just add salts by measuring spoons:). Not very accurate, but accurate enough. Accuracy is an illusion anyway, as you have no way of knowing how much minerals are added by your grains.

That's true,  but it would also affect volume measurements wouldn't it? And I totally agree with your comment about accuracy.

You may be right there. I've sort of been imagining the water seeping into empty space between the mineral molecules. We need a chemist here, there are too many people like me - been teaching Norwegian language and litterature, history and philosophy - around;).

I have some chemistry background. I would think the water would be absorbed by the minerals and make them swell.

I don't think it's that simple, since hydrated salts are typically more dense than anhydrous (sometimes significantly so). The issue with volume measurements is that grain size and shape (and therefore the empty space in between) has a significant role. Without knowing the extent of hydration of the salt and its affect (if any) on the size and shape of the crystals, there's just too many moving pieces to make a solid rule of thumb estimate. And it very well may go in different directions for different compounds as well.

As a teacher, there were a few basic truths I tried to hammer into the heads of my pupils. One of them was that you should never expect a question to have a simple answer. It's nice to have that confirmed .

You may still have to settle for a simple solution to a problem, but it's very important to know that that's a compromise - and that there may be other solutions. I'll go on measuring my salts with spoons, but I'll still drink the beer of my neighbour who prefers weighing them:).

[ynotbrusum]

As a teacher, there were a few basic truths I tried to hammer into the heads of my pupils. One of them was that you should never expect a question to have a simple answer. It's nice to have that confirmed .

And then there is Occam’s razor….

[Finn Berger]

As a teacher, there were a few basic truths I tried to hammer into the heads of my pupils. One of them was that you should never expect a question to have a simple answer. It's nice to have that confirmed .

And then there is Occam’s razor….

Absolutely . So I used to let them watch "The Name of the Rose" - the film, that is -  too . That's a beautiful portrait of a true hero. And it teaches you the essence of what science is about.

Damn, we're getting off topic here:).