RogueRose
International Hazard
Posts: 1590
Registered: 16-6-2014
Member Is Offline
|
|
Bulk/commodity (snow melt type) CaCl2 excellent for dessicant after high temp heating
Pics & video are on the way
The CaCl2 I have is thin flakes and is about $7-9/50 lb in the winter. I tried to use it as a desiccant in a number of applications and was severely
disappointed. Prior to my first usage attempts I baked in oven at high for 12 hours (should be well over 500F maybe 550-575). It remained in its
flake form and could be broken up by pressing down with a pan or something flat. I never weighed water loss unfortunately.
Second try I heated the same CaCl2 over a wood fire (much higher BTU and probably 1000-1300F on the grill above the fire. The salt started to look
like thick white oatmeal and wa steaming profusely. Stirring continuously, or 10 seconds on - 30-45 seconds off, is helpful for faster and more even
completion. If allowed to sit, it may melt but it will form a hard crust on the bottom, very difficult to remove while very hot yet chip off very
nicely once cooled 300-500 degrees from high temp. Pieces can be broken up easily but there will be no flakes. I used a hatchet to chip at the
solidified mass on the bottom and with little effort it removed in large chunks. Immediately after breaking up solids (while still VERY hot
700-1000F) place in an air-tight metal container or other heat-proof container.
In one pan, all loose pieces were dumped and the bottom 1/4" coating was allowed to remain. Within 30 mins, while sitting outside, there was about
30-40ml of liquid (this is a 4" diameter pan, so not large at all, and total surface area was limited as the layer was a pretty smooth surface - not
tons of surface area like with 1/4" of granules or flakes on the bottom). The humidity was probably 50-70% with little wind movement so I consider
30ml of liquid a very significant amount in that 30-40 mins.
As a comparison to the first run months ago, I saw "dew" droplets start to appear on the flakes after about 3-4 hours at ~45-55% humidity (although
temp was about 10 degrees cooler then).
So, I just wanted to make it known that the CaCl2 used as ice melt seems to be very useful when processed to remove the crystallized water. There
should have only been 1 H2O molecule difference between the 2 batches and I can't understand how there is so much difference in performance.
I'll post some pics and results of some testing. When heating over wood flame, there is a very little bit of carbon attracted to the salt but as this
isn't going to be mixed with anything - only used to filter/dry air - I don't see that being an issue (I do the same with MgSO4 and it works very
well, much better than in an oven).
|
|
|
NEMO-Chemistry
International Hazard
Posts: 1559
Registered: 29-5-2016
Location: UK
Member Is Offline
Mood: No Mood
|
|
maybe one is calcium oxide?
|
|
|
RogueRose
International Hazard
Posts: 1590
Registered: 16-6-2014
Member Is Offline
|
|
No, they came from the same bag, of that I am certain.
I'm going to do some tests with the same setup I had before, but smaller (proportions will be equal though).
I know it wasn't CaO for sure, as I don't have that. If anything it would have been Ca(OH)2 but that is a fine powder vs the large flakes of the
CaCl2.
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by RogueRose  |
I know it wasn't CaO for sure, as I don't have that. If anything it would have been Ca(OH)2 but that is a fine powder vs the large flakes of the
CaCl2. |
Physical form isn't a great way to identify a compound by. Just check pH: CaO reacts very alkaline, as it's a strong base.
The various hydrates (1,2,4 and 6) of CaCl2 have strongly differing MPs, so you should be able to identify what you've got that way.
Much of the 'road CaCl2' is a byproduct of Solvay process Na2CO3, so it's likely to be quite contaminated with NaCl.
[Edited on 8-7-2016 by blogfast25]
|
|
|
Acuyo
Harmless
Posts: 29
Registered: 29-6-2016
Member Is Offline
Mood: activated
|
|
| Quote: Originally posted by blogfast25 | | Quote: Originally posted by RogueRose |
I know it wasn't CaO for sure, as I don't have that. If anything it would have been Ca(OH)2 but that is a fine powder vs the large flakes of the
CaCl2. |
Physical form isn't a great way to identify a compound by. Just check pH: CaO reacts very alkaline, as it's a strong base.
The various hydrates (1,2,4 and 6) of CaCl2 have strongly differing MPs, so you should be able to identify what you've got that way.
Much of the 'road CaCl2' is a byproduct of Solvay process Na2CO3, so it's likely to be quite contaminated
with NaCl.
[Edited on 8-7-2016 by blogfast25] |
Good to know but for drying this shouldn't really be a problem, I'm guessing?
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
No, it shouldn't. NaCl forms no hydrates.
|
|
|
RogueRose
International Hazard
Posts: 1590
Registered: 16-6-2014
Member Is Offline
|
|
I found an analysis of the bag and it says "garunteed minimum 77% CaCl2" - may contain various amounts of the following:
NaCl
KCl
SrCl2
water
CaCl2 info
Hydrate level - Density - Melting Point/decomp point
Anhydrous - 2.15g/cc - 772-775C (1,935C boiling point)
monohyd - 2.24g/cc - 260C
dihyd - 1.85 g/cc - 175C
tetrahyd - 1.83g/cc - 45.5C
Hexahyd - 1.71g/cc - 30C
I'd like to do some test to see how much of the 23% is crystiline H2O - so I'll measure say 200g then heat till melted, seal in airtight container,
weigh again.
If this product is the Hexahydrate, that would mean 21% is H2O leaving less than 2% contaminates which is really pretty pure in my book for a $9 bag
(1lb of 98% CaCl2 has been sold on Amazon for $25 I've seen)
Here is information on the other listed "contaminates"
SrCl2 - forms di and hexa hydrates hexahydrate melts at 61C MP of 874 is listed as anhhydrous but IDK if that means at that temp the dihydrate
looses the H20 to form anhydrous and melts at the same point??
SrCl2 - Strontium Chloride
Hydrate level - Density - Melting Point/decomp point
Anhydrous - 3.052 g/cc - 874C (BP 1,250C)
dihydrate - 2.672 g/cc - MP/decomp??
hexahydrate 1.93 g/cc - 61C
NaCl
no hydrates, 2.165g/cc, MP 801C, BP 1,413C
KCl
no hydrates, 1.984 g/cc, MP 770C, BP 1,420C
|
|
|
blogfast25
International Hazard
Posts: 10562
Registered: 3-2-2008
Location: Neverland
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by RogueRose | I found an analysis of the bag and it says "garunteed minimum 77% CaCl2" - may contain various amounts of the following:
NaCl
KCl
SrCl2
water
CaCl2 info
Hydrate level - Density - Melting Point/decomp point
Anhydrous - 2.15g/cc - 772-775C (1,935C boiling point)
monohyd - 2.24g/cc - 260C
dihyd - 1.85 g/cc - 175C
tetrahyd - 1.83g/cc - 45.5C
Hexahyd - 1.71g/cc - 30C
I'd like to do some test to see how much of the 23% is crystiline H2O - so I'll measure say 200g then heat till melted, seal in airtight container,
weigh again.
If this product is the Hexahydrate, that would mean 21% is H2O leaving less than 2% contaminates which is really pretty pure in my book for a $9 bag
(1lb of 98% CaCl2 has been sold on Amazon for $25 I've seen)
Here is information on the other listed "contaminates"
SrCl2 - forms di and hexa hydrates hexahydrate melts at 61C MP of 874 is listed as anhhydrous but IDK if that means at that temp the dihydrate
looses the H20 to form anhydrous and melts at the same point??
SrCl2 - Strontium Chloride
Hydrate level - Density - Melting Point/decomp point
Anhydrous - 3.052 g/cc - 874C (BP 1,250C)
dihydrate - 2.672 g/cc - MP/decomp??
hexahydrate 1.93 g/cc - 61C
NaCl
no hydrates, 2.165g/cc, MP 801C, BP 1,413C
KCl
no hydrates, 1.984 g/cc, MP 770C, BP 1,420C |
Assuming your product is indeed 'Solvay CaCl2' then NaCl will by far be the most prominent contaminant.
Solvay converts limestone (crude CaCO3) and sea salt to sodium carbonate:
CaCO3 + 2 NaCl === > CaCl2 + Na2CO3
Both raw materials of course contain K, Mg, Sr in quite small quantities, that can end up in the byproduct of Solvay soda production,
CaCl2, but it's a reasonable assumption that the bulk of non-Ca will be Na. The rest is probably trace elements.
You could try and recrystallise the product but with such high solubility limit and a flat S,T curve that isn't easy with CaCl2.
[Edited on 9-7-2016 by blogfast25]
|
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
