cacl2 2h2o density

mbsun · Sep 11, 2015

Ok if i add 2kg of cacl2 2h2o to 4 litres of ro, the calcium chloride should displace 1093ml of water (2000g÷1.85g/cm3)

But it doesnt, and not according to the balling lite manual where you add 50ml of trace and then top up to 5l

So my 1093ml cant be correct.
Its late and i cannot figure!

Randy Holmes-Farley · Sep 11, 2015

No, you cannot do math like that. Dissolved solids can take up much less space than the same undissolved solids. Some times they take up no apparent space at all, pulling the water molecules closer together.

What is it you actually want to determine?

mbsun · Sep 12, 2015

Thanks randy

I guessed i could not, as i was clearly wrong

Could you tell me how to do it?

In this case my question would be- what would the finished volume of 4l ro plus 2kg of cacl2 2h2o be?

Randy Holmes-Farley · Sep 12, 2015

That would involve looking up the final density of the solution.

The solution you are making contains about 1510 grams of calcium chloride and 4490 grams of water, or about 25.2% calcium chloride by weight.

A 25% calcium chloride solution has a density of about 1.24 kg/L at 25 deg C.

which is from:

http://www.prog-univers.com/IMG/pdf/CalciumChloridHandbook.pdf

So since you have a total of 6,000 grams, the volume would be about 6 kg/1.25 kg/L = 4.8 L .

mbsun · Sep 12, 2015

That makes sense, and is much appreciated, thankyou randy

The final question-

Where could i obtain these tables for other chemicals like magnesium chloride, sulphate, potassium chloride, sodium bicarbonate for example?

Randy Holmes-Farley · Sep 12, 2015

You're welcome.

I have a big book called the CRC Handbook of Chemistry and Physics that has many such tables. Some you may be able to find online as I found the calcium chloride data.

JimWelsh · Sep 12, 2015

I have created a spreadsheet using the data from the tables in the CRC Handbook, which can calculate the density and refractive index of any concentration of solutions of various individual salts at 20C. Plugging your numbers into my spreadsheet, I get very similar numbers to what Randy got (of course). I got 25.19% (w/w) CaCl2, density at 20C of 1.23, and volume at 20C of 4.87 L. The spreadsheet handles all the salts you mention, except not NaHCO3 (yet).

Randy Holmes-Farley · Sep 12, 2015

JimWelsh said:
I have created a spreadsheet using the data from the tables in the CRC Handbook, which can calculate the density and refractive index of any concentration of solutions of various individual salts at 20C. Plugging your numbers into my spreadsheet, I get very similar numbers to what Randy got (of course). I got 25.19% (w/w) CaCl2, density at 20C of 1.23, and volume at 20C of 4.87 L. The spreadsheet handles all the salts you mention, except not NaHCO3 (yet).

Were you trapped in a one room cabin for a week by a hurricane?

mbsun · Sep 12, 2015

JimWelsh said:
I have created a spreadsheet using the data from the tables in the CRC Handbook, which can calculate the density and refractive index of any concentration of solutions of various individual salts at 20C. Plugging your numbers into my spreadsheet, I get very similar numbers to what Randy got (of course). I got 25.19% (w/w) CaCl2, density at 20C of 1.23, and volume at 20C of 4.87 L. The spreadsheet handles all the salts you mention, except not NaHCO3 (yet).

Is this available?
I would appreciate it if it was, but i quite understand if not- your work

Randy cheers

Been a great help

JimWelsh · Sep 12, 2015

@Randy: Funny. This is my way of making sure I understand a concept thoroughly; I create a spreadsheet that works the numbers backwards and forwards various ways, and then compare my calculated results to empirical data, to make sure I "got it right". In this case, I was actually more focused on studying refractive index than density, but I had data for both, so......

@mbsun: It's not so much about protecting "my work", as it is that my spreadsheets tend to suffer from a certain conceptual "sprawl" that would make them extremely unfriendly, intimidating, confusing, or perhaps even amusing to others. It would take work I'm not sure I'm prepared to do to make the spreadsheet "presentable". If you had hypotheticals for other salts similar to the one you described above for CaCl2*2H2O, I'll gladly oblige you.

Randy Holmes-Farley · Sep 12, 2015

FWIW, the fact that solid calcium carbonate dissolving into seawater takes up less volume than the same amount of seawater plus solid calcium carbonate has huge implications for the ocean.

Specifically, in the deep ocean, the pressure is so high that it causes calcium carbonate to dissolve simply because the high pressure forces the rock to dissolve so that it takes up less volume. For this reason, calcium carbonate shells and such that fall from the near surface to the bottom of the deep ocean dissolve on the way down, and calcium carbonate does not build up layers in the deep ocean even though it does near the surface such as on coral reefs.

mbsun · Sep 12, 2015

JimWelsh said:
@Randy: Funny. This is my way of making sure I understand a concept thoroughly; I create a spreadsheet that works the numbers backwards and forwards various ways, and then compare my calculated results to empirical data, to make sure I "got it right". In this case, I was actually more focused on studying refractive index than density, but I had data for both, so......

@mbsun: It's not so much about protecting "my work", as it is that my spreadsheets tend to suffer from a certain conceptual "sprawl" that would make them extremely unfriendly, intimidating, confusing, or perhaps even amusing to others. It would take work I'm not sure I'm prepared to do to make the spreadsheet "presentable". If you had hypotheticals for other salts similar to the one you described above for CaCl2*2H2O, I'll gladly oblige you.

Thats fine i understand.

The things i do in my kitchen, reefing homebrews i suppose, that i do for the fun of it to see if i can turn (my) theory into fact are equally (well not equally clearly as some knowhow needs improving) sprawling or hard to understand if you didnt write them

In actuality the cacl2 2h2o was something i spotted on a forum that made it clear to me what the flaw was in my attempt to work a homebrew salt mix back from a finished volume to a start volume

In order to do this i need to find myself or draw myself a compendium i think, inc nacl and nahco3

Hope google is my friend, may take a while, but all good fun