Calcium Nitrate

Thoughts On Calcium Nitrate

I’ve found this salt a little tricky to work with. Was easy enough to prepare. I gradually added 500g. of calcium carbonate (agricultural lime/ crushed limestone) to 2 litres of 25% nitric acid which neutralized the acid giving dissolved Ca nitrate plus CO2 and water. I then just evaporated off the water in a large evaporating dish over a low flame on my kitchen stove. When the salt was solid and half dry, I took a break for about an hour and turned off the stove. When I came back I noticed that the partly dry Ca nitrate had absorbed a good quantity of water already out of the room in a very short time. So far, so good… this is what we are looking for. So I turned on the stove to low again and proceeded to further take the salt to complete dryness, all the time stirring the drying salt with a spatula. On one occasion I got some of the salt a little too hot and I could see it decompose to give the toxic brown fumes of NO2, so I turned the heat down to minimum, and kept drying until all salt was a pale pink color but still a bit lumpy. I then ground it further on cooling in a mortar & pestle, and quickly covered it with plastic wrap to stop moisture absorption.
That night (full moon) I placed it in my “dew pond” in a large evaporating dish next to my bags of ice, to absorb full moon dew. See photos.





To my disappointment, the Ca nitrate had absorbed little or no dew overnight, even though I collected over 200ml in the “pond”? This salt doesn’t suck! So, what gives? I’m trying to figure it out. I don’t believe I decomposed it all into oxide since that takes over 500°c., but maybe it sucks better when slightly hydrated already? Or maybe I’m just hyper and it needs patience, like 7 days under the stars? Already tonight, it’s looking a bit damper.

Nice work. Your calcium nitrate seems to have some impurity cause it is brown (when pure, it is white) but I hope this will not interfere with the dew collection.

Quote :

To my disappointment, the Ca nitrate had absorbed little or no dew overnight

I have observed for potassium carbonate, that it passes through a period of moisture collection when nothing visible happens and then, "suddenly" it turns into liquid. Maybe the same happens with the CaNO3. It takes some days, especially when you have a lot of the salt concentrated in a small bowl.

Calcium nitrate seems to have aprox. the same solubility in water than potasium carbonate (1,1 g/ cc). But potasium acetate has 2g/cc, and is very deliquescent (actually, it is very difficult to keep it dry). However, I have no experience trying to get and distil dew from it, so perhaps it's not as useful as it seems. But it may be worth a try.

Calcium nitrate is able to absorb a great deal of water, which you will see floating on the surface. No other salt has worked as incredibly as calcium nitrate in my experience of collecting dew.

You just have to give it a week, and you will see that it keeps collecting water even when you think it's done.

Even sitting inside in a room with very low humidity the calcium nitrate will fill up the container with water in about a week. Potassium carbonate on the other hand starts to loose water and dry up when I bring it back inside.

Hi luce7,

congrats on that really nice dew pond.

May I ask at which temperature you gathered 200ml dew.

And this huge bags are filled with ice?


Wilfried

Wilfried wrote:

Hi luce7,
congrats on that really nice dew pond.
May I ask at which temperature you gathered 200ml dew.
And this huge bags are filled with ice?
Wilfried

Hi Wilfried,
It’s getting to be mid-summer here in south eastern Australia and night-time temperatures jump around a lot, but I guess lately the night-time lows have averaged around 12°c (54°F) when I’ve harvested dew in my tiny rural valley. The big bags of ice haven’t added much to the yield lately and the plastic sheet has been collecting micro droplets which only pool into one corner when I shake down the sheet. So really this info is pretty useless to you or anyone else since there are so many variables of weather, season and locality. Conditions in my valley are very variable, and we almost never get snow in winter, just light frosts early morning of down to -3°c (27°F). Our climate here is kinda like northern California, but getting dryer due to climate change.

Nonetheless thank you luce 7 for the info.

Wilfried

I’m interested in using Calcium nitrate but I have neither the resources nor proper knowledge in chemistry to make it. Does anyone happen to know if and where it can be purchased? I did find this website (http://www.sciencestuff.com/prod/Chem-Rgnts/C1448) but I was wondering if I can buy it anywhere else? I have been trying everything to collect dew and its proven quite impossible. I must live in dry valley or something.

best price found so far:

hi valley chemicals

http://store.hvchemical.com/search.htm?searchterm=calcium+nitrate&goButton=go&step=2&ViewFrom=1&NumResults=10

CALCIUM NITRATE 500 G REA/ACS 4-HYDRATE 777550 $27.85