Randy's 2 Part DIY

[Reefiez]

I got my hands on some pharm grade calcium chloride 2 hydrate (99%-103% assay).

I am not a chemistry person, so I am looking for some input on whether my calculation or assumptions are correct.

Randy's recipe uses dowflake, which is 77-80% calcium chloride (by weight).

My first instinct is that mine is ~100%, which is ~20% purer than Randy's. So I just decrease the amount of powder to dissolve accordingly. Instead of 2.5 cups per gallon, just 2 cups.

But then I thought, I think I'm missing something, where did the 2 water molecues go?

So I googled a periodic table and searched the atomic weight of the elements, and calculate the calcium chloride portion (assuming 100% purity for simplicity).

CaCl (H2O)2 will have an atomic weight of 111.56
CaCl has an atomic weight of 75.53

Assuming 100% purity, CaCl by weight is 0.677, or 67.7%.

67.7% is about 10% LESS than Randy's Dowflake of 77-80%.

Does this mean I should add the ~10% MORE, so 2.75 cups?

I haven't touched chemistry for over a decade, am I over-thinking this? Could someone point me in the right direction?

Thanks a lot!

 

[dodgy67]

I started to use Rand's 2 part recipe about a 18 momths ago just bought some Calcium Chloride Dihydrate and Sodium Bicarb., I would assume as long as you can dissolve the correct amount in a gallon of RODI and I started off with 1ml per gallon of each spread over the day with a dosing pump, as long as your testing your Ca on a regular basis you can adjust if its too strong or too weak a solution

 

[bertoni]

You should be very close with about 20% less. Randy's recipes are based on calcium chloride dihydrate, which I think is what you have. You might need to do some tuning.

 

[Reefiez]

ok, i just found a huge mistake in my calculations! i missed an extra chloride lol!

seems that randy's recipe is spot on even for a 100% calcium chloride dihydrate without modification. i believe the difference would be less than 5%, which is pretty insignificant.

my mistaken calculation was that CaCl2 (H2O)2 is 147.01g/mol, with CaCl 110.98g/mol. CaCl by mass would be 110.98/147.01, coming to 75.5%, which is pretty close to Randy's 78.5%. I assume the difference is due to a little less moisture in the dowflake product. fine tuning will probably be needed.

thanks for the input dodgy67, and also bertoni for always answering so quickly!