How to calculate the weight of a certain mineral in a compound? e.g. Ca in gypsum?

[Miles_1111]

Say if I add 10g of Cacl2, 6g of gypsum and 6g of epsom, how to calculate the individual weight of Ca, Mg, SO4, CL, etc? If it is complicated, could you recommend any convenient software (online or off line) to do the math? Thanks.

 

[Silver_Is_Money]

It isn't complicated. It requires knowing the molecular weight (also called molar mass) of the molecular compound, and the molecular weights (molar masses) of each of the atoms that reside within the compound, plus the counts of each atom within the molecular compound.

For CaCl2, the compounds (molecules) molecular weight is 110.984
For Ca++ the molecular weight is 40.078
For Cl- the molecular weight is 35.453

Such that: 1*40.078 + 2*35.453 = 110.984

Ratio to determine the quantities of each individual component within 10 grams:

Ca++ = 10 * 40.078/110.984
Ca++ = 3.611 grams

Cl - = 10 * (2*35.453)/110.984 [notice that you must multiply Cl times 2 since there are 2 atoms of Cl present]
Cl- = 6.389 grams

A quick proof check:
3.611 grams + 6.389 grams = 10 grams

Here is a great website to help you:
https://www.convertunits.com/molarmass/

When you launch this website, you simply enter the chemicals formula in the box and click on "Get molar mass". A lot of detailed information will follow that will be a great aid to you in your quest. Everything you need to determine individual component grams should be available through this website. All you need to know initially is the correct chemical formula. It should make your quest even easier than using the method I showed you above, as (among other things) it provides you with "mass percent". Multiply mass percent times your grams to get individual atoms weights in the compound as grams. Results will match my example above, but will be easier to do overall.

 

[Silver_Is_Money]

From there you can compute the PPM (Parts Per Million, the equivalent of mg/L) of the Ca++ and Cl- for a given amount of water to which you have added them.

Example:
Distilled water, 35L volume.
10 grams CaCl2 added

Ca++ = 3.611 g = 3,611 mg
Cl- = 6.389 g = 6,389 mg

Ca++ = 3,611 mg / 35L = 103.2 PPM (mg/L)
Cl- = 6,389 mg / 35L = 182.5 PPM (mg/L)

 

[Miles_1111]

@Silver_Is_Money Briliant! Many thanks man. One more question is that should I add the salts ( 10g of Cacl2, 6g of gypsum and 6g of epsom ) at all mashing? or add them at mashing, sparge and boil separately?

 

[Miles_1111]

Say if I aim to get 10L wort into the fermentor. Use 18L RO water in total = 12L as mashing water + 6L as sparge water ( I will get 7L first wort and overall 13L before boiling. ). Should I calculate the PPM for salts according to 18L? 10L or 12L?

 

[Silver_Is_Money]

Calculate PPM as for 18L, or whatever the sum total amount of initial water happens to be. I mineralize my mash and sparge water equally as to PPM (or did so when I sparged, which I no longer do). I have never added any minerals to the boil. Now that I've gone no-sparge, all of my minerals go into the mash water.

The general consensus is that at least 50 PPM of Ca++ is required in the mash water.

You will also need to consider mash pH adjustment. There are many mash pH software assistants available. I'm of course highly biased, being the author of one of these software solutions, but while you are evaluating several of them please also give consideration to evaluating mine. It is free. Such software also does the mineralization PPM (mg/L) calculations for you.