CHRIS25
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Sodium Silicate Solubility Problems
I took delivery of sodium silicate powder. I have spent the last 3 days working out solubility calculations so that I can get an accurate molarity
for experiments namely silica gel and crystal garden to begin with. The info that came with the chemical states that it has a 2.4 SG.
Internet searches given for various solubility data at 20c range from 150g/L to 100g/L based upon obscure graphs. My initial tests were:
10mLs at 10c 0.7g
30mLs at 20c 1.2g
400mLs at 25 - 35c 2.3g
This seems so wrong I think. Especially when practically every paper I read speaks about Na2SiO3 as being highly soluble in water.
A recent study about making silica gel for example stipulated an optimum reaction as follows:
"Mix a 1.2 SG sodium silicate....." This is 20g plus 100mLs of water and is a 1.67M concentration (unless my maths is all wrong).
Since there is no information at all about what molarity (or percent by weight or V/V) given anywhere at all when papers talk about a saturated
solution of sodium silicate this is all becoming quite confusing. Although I did come across one paper that mentioned a solution 30-40% weight
sodium silicate, which could mean either grams solute per 100mLs water (40g and 60mLs water) or percent solute per 100mLs water (40g plus 100mLs
water.
Either way this whole solubility issue with sodium silicate seems to be a confusing mess, something I have not come accross in any chemical to date.
Please could someone help me here.
[Edited on 8-4-2013 by CHRIS25]
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
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The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
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elementcollector1
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Perhaps you should try solubility at different temperatures?
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CHRIS25
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Hi I did: My initial tests were:
10mLs at 10c 0.7g
30mLs at 20c 1.2g
400mLs at 25 - 35c 2.3g
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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elementcollector1
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I don't follow. You changed temperature and volume? Or temperature and mass? Only one thing should be the variable: Use the same volume and total mass
for each trial, then increase the temperature, measuring at each 10-degree step how much has dissolved (hint: |final-initial|)
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S.C. Wack
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Not the Merck Index.
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macckone
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The ratio of sodium oxide to silica oxide will determine the solubility.
The most soluble form is Na2SiO3.
This form is also referred to as sodium metasilicate.
The less soluble forms contain less sodium hydroxide.
The solubility can be increased by adding sodium hydroxide if you have a less soluble form.
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CHRIS25
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EC: No neither, these were three different tests. Besides I am really trying to understand the innaccurate portrayal of sodium silicate as a readily
soluble substance in water when it is not, also as below, how is a specific gravity of 1.43 achieved in such conditions, if I am understanding SG
correctly which would imply 143g total weight and therefore 43g/L of Sodium silicate?
SC: That is the most constructive thing I have read concerning the solubility of silicates, no more explanation needed. So many chemistry papers
that I have read have constantly referred to Na2SiO3 with adjectives such as - "highly" "readily" "easily" soluble (especially at high temperatures).
This was misleading. It's practically insoluble really and how on earth do they achieve a SG of 1.43 if this is so difficult to dissolve?
MAC: Thankyou, I am aware about the ratios of NaO to SiO and their different effects on reactions but did not know that solubility was affected to a
great degree. Also Metasilicate and silicate are interchangeable terms according to some. it Seems a bit contradictory that if it contains sodium
hydroxide and this affects solubility how does adding more improve the situation - nevermind.
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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macckone
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The solubility of the Na2SiO3 form is 150g/L @ 20C.
That is pretty soluble. Unfortunately it sounds like you have the neutral sodium silicate that is much less soluble and not the metasilicate.
Although the terms are used interchangeably, the metasilicate is a specific sodium oxide to silicate ratio while sodium silicate (the generic) is not.
http://apps.kemi.se/flodessok/floden/kemamne_eng/natriumsili...
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CHRIS25
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Hi MC, that must be it, and thankyou for that link, will read and digest; today I placed 0.6g into 100mLs water at 60c. About 0.4 dissolved, the
solution was cloudy and with a clearly undissolved residue on the bottom, so I added 0.3g NaOH and immediately everything dissolved and I was left
with a clear solution. So I got over-zealous and added another 1.8g of sodium silicate, which obviously did not dissolve, so I had to add 28g of NaOH
just to get about 70% of that to dissolve, seemed pointless taking this any further and ending up with a sodium hydroxide solution rather than a
sodium silicate solution; so I filtered the solution and it now sits on my table with a strong golden amber like colour and a thick viscosity.
So from what I can gather sodium silcate anhydrous is in fact for all intense and purposes Insoluble in water and this is infuriating that the correct
terminology is not used even in professional documents. Unless I can create a huge pressure and 150c temperature (how do yo do that with water?) I
simply can not dissolve it.
I have managed to get 2.2g to dissolve in 100mLs of water, that's nothing. Not even the chemical company that I bought it from made any distinction
as to what kind of silicate this was, I simply assumed that everywhere where people referred to sodium silicate this was in fact Sodium silicate,
especially when referring to Crystal gardens - not so - infuriating inaccuracies all over the web, including wikpedia.
[Edited on 10-4-2013 by CHRIS25]
[Edited on 10-4-2013 by CHRIS25]
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
|
|
|
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