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Density of solutions of dissolved solids (NaCN, Lime, SMBS)

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Aug 29, 2005
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Hi guys, I need a way to detirmine the density of a solution in which I have dissolved solids to a certain w/w concentration- be they Sodium cyanide, Lime (hydrated), and Sodium metabisulphite (SMBS).

Where would I look for this information?

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Try the CRC Handbook or Lange's Handbook of Chemistry.
 
Normaly you will not get data about your particular system. If you would like the density at one single point then it is the fastest way to find a graduated flask, fill it with your solution and put it on a ballance.Then I hope you know how to calculate the density.
If you would like to have a three component diagram at various temperatures then you should prepare the experiment more carefully and with more equipment;a direct read-out electronic density meter would help you a lot because you will probably repeat measurements a few times. You should select the range of your concentrations. For most effective work search for "Design of experiments.mixtures" that you can find in almost each statistical software. Prepare solutions and repeat density-temperature scans.Design of experiments.Analysis tools will help you to prepare a result expresed as a function density=f(x1,x2,x3,T).
m777182
 
It is not a 3 component system, it is just a normal 2 component system.

i.e. I want the answer to- what is the density of a 15w/w% solution of SMBS at 20C?
What is the density of a 20w/w% solution of sodium cyanide at 20C?

I find it hard to believe that this info is not listed somewhere? I do not have access to experimental apparatus, as we are simply in the design stage.

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Have you tried looking at the literature for NaHSO3 yet? When you dissolve Na2S2O5 in H2O it reacts to form NaHSO3.

Sodium Metabisulfite is a white, or offwhite, finely crystalline powder with a faint sulfur dioxide odor.

What strength is your hydrated lime slurry?
 
As an approximation, if the solid dissolves without a large (either - or +) heat of solution, just use the total weight & the volume of the liquid. I.e.,

"density of a 15w/w% solution of SMBS at 20C?"
--- SG ~ 100/85 = 1.176
"What is the density of a 20w/w% solution of sodium cyanide at 20C?"
--- SG ~ 100/80 = 1.25

Experimentally, I first use a wide range SG hydrometer, SG 1.00-2.00. Then use a narrow range hydrometer, e.g., 1.080-1.150 to control a zincate solution of desired SG 1.120, for more precision. SG hydrometers:

Of course, with slurry you have 2 SG values. If you let settle, you can get the SG of the solution per se (at saturation dissolution). If keep stirring, get the slurry SG, i.e., that of the solution containing suspended solids.
 
cub3head- the hydrated lime slurry is at 15 w/w%

Kenvlach, I did that, but acc to my calcs dissolving lime (For example) causes the volume of the solution to DECREASE ...


eg.
start with 17T of water ~17m3
Dissolve 3T of Lime in it to make up 15 w/w% solution

SG lime (solid) = 2.3
SG Water (l) = 1.0

SG Mixture = 2.3*15%+1.0*85% = 1.2

therefore volume of a 20T solution of 15w/w% lime = 20/1.2=16.7m3 .... LESS than the water you added in the first place, which, I have been told is not practically observed (i.e. you add lime bags to a tank of water, and the level of the solution increases).


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First, your math is wrong. For the approximation, the volume is fixed at the initial volume of water:

SG ~ 20/17 = 1.176

Second, when you quickly dump solids into a volume of water, the gross volume will of course increase. It will then decrease as dissolution occurs. For strongly exothermic dissolution, the total volume can even be less than the initial volume of water (after the solution has cooled back to original T).

Third, lots of data on the Internet. E.g.,
"At 20 degrees C, hydrated lime has a solubility of 0.165 grams per 100 grams of saturated solution."
--- Since the solubility is so low, the volume of the slurry will be significantly greater than the initial volume of water. But, still less than the gross or total volume. Maybe a 5% decrease just for getting rid of the air in the powdered lime.
Do a search.
 
Firstly, I'm not quite sure why you have taken such an agressive tone, I was simply asking a question

Secondly, my maths is not wrong, I have simply made an assumtion- just as you have in assuming the volume of fluid does not change in arriving at your SG = 1.176 figure ... this does not help me as it is the final volume of solution that I want to know in the end - I can't just assume it!

Thirdly, I have searched on the internet, and have not found the solution density stated clearly anywhere ...

Finally,
"Since the solubility is so low, the volume of the slurry will be significantly greater than the initial volume of water"

Thank you, for some reason my reference has the solubility of lime at 16g/100g so I assumed it would all fully dissolve ... (somobdy missed a few decimal places!). In that case Iguess it would be reasonable to assume that none of the lime dissolves (for arguments sake) and the slurry is just a suspension of solid particles. therefore

17T of water =17m3
3T lime = 3/2.3 = 1.3m3

density of mixture (Slurry) = 20/(17+1.3) = 1.09 t/m3

That is now the 3rd value we have got!

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I'm sorry; I was a bit blunt because you hadn't used the approximation as given. It's a moot point, anyway, as it only applies to solutions, like the sodium compounds in water. For the solution phase of the lime slurry, handbooks give a density of 1.00007 g/cc at 20 C [data for a 0.15 wt% Ca(OH)2 solution, slightly below saturation], so the dissolved portion is negligible in comparison to the solids.

More info can be found by searching the Internet. E.g.,

"A lime slurry with a density of 35% solids will weigh approximately 10.3 pounds per gallon and contain 3.6 pounds dry solids per gallon." --
This bit of data gives SG = 1.10 for 15% solids by linear interpolation. So, your 3rd value is quite reasonable.
 
Great! thanks- one down the other two to go! Both SMBS and NaCN will fully dissolve (unless someone has missed a decimal point again- but I doubt it!)

Cub3bead: I couldn't find any solution density info for Sodium bisulphite (as opposed to SMBS) either?

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