1)PPM is weird, it sounds like it means "number of solute molecules per 1,000,000 solvent molecules", but I don't believe that it does. Whenever I've had to use PPM, I was told it was based on mass, so: PPM = mg solute/kg solvent = mg solute/1,000g solvent = mg solute/1,000,000mg solvent.
Thank you for replying, and especially the links. I will spend some time there trying to understand the topic better.
Your reply came at a great
time because I was going to post another topic asking about PPMs.
I know I can mix 1g of ordinary table salt in 1L of pure (distilled) water, and produce about 1000ppm (accounting for how table salt may not be as pure as what would really be used to make calibration fluids. I calibrate my TDS meter this way. It's close enough for what I do.).
But, something I don't understand is when something like epsom salt (MgSO4
O) is dissolved in water.
Can the expected PPMs from 1g be calculated? Does the O4
O become "parts?" (Like the Mg and S?) Or, does it absorb into the water as dissolved oxygen which is then released into the atmosphere?
Does the Mg and S "parts" produce the same PPMs as NaCl?
For example, I know Epsom salt contains 10% and 13% Mg and S (by weight). So, should I expect 1g in 1L to produce 230 PPM (compared to 1g of NaCl producing 1000 PPM)?
I know TDS/PPM is a kludgey way of expressing electrical conductivity (EC) in gardening. But, the general rule is to multiple EC by 1000 and divide by 2. (1 EC = 500 PPM). I can live with that kind of vaguery.
But, what I have trouble with is how to predict (calculate) what a particular element will produce. I.e., the exact steps. It seems like it involves knowing the percent of mass, how many atoms are in a gram(?). But, what happens to things like H and O? Do they not count?
Sorry if I don't make sense. I'm trying to understand how, if I add 1g of K2
O (a common form of potassium in gardening), what "strength" will it be. (So, a ratio of K to N, which comes from calcium nitrate, Ca(NO3
, could be predicted.).
Thanks in advance!