Hi,

There is a difference. Explain to the farm co-op what your intentions are and that you need a water soluble calcium nitrate. They may call it either greenhouse or technical grade calcium nitrate. If you buy stuff that was intended just to be thrown into a garden or field it won't dissolve that easily and you will probably end up with a gunky mess. If you buy calcium nitrate from the co-op make sure it's intended for what you want to do.

Different grades of chemicals exist based on purity. For hydroponic gardening you don't need to worry about using anything extremely pure. People working in the cosmetic and pharmaceutical industries however need to buy higher grades. Chances are the chemical store gave you the price of something more pure than you need.

Here is an explanation of some different chemical grades. You can always ask what grade of a chemical you are buying and the seller should be able to tell you.

http://secure.sciencecompany.com/Chemical-Grade-Designations-W53C665.aspx

The Calcium Nitrate sold by the chemical supplier is most probably lab grade. One part of the price difference may also be due to retail price (per kg) and different profit ranges (very common in EU). Fertilizer grade CN that is commonly used for nutrients is cheap and 23 Â for 50kg seems right.

I actually confirm what bilberrybrian said, except that I doubt that the co-op product may not be suited. Any grade of this component has a good water solubility and is suited. Asking doesn't do any harm though,- but while you are at it, also ask about percentage of Ca and N and exact purity (ca. 95-97%). This may be very useful when doing your maths later!

When buying Calcium Nitrate in bulk size, be aware that this component is extremely hygroscopic! I'd recommend that as soon as you open the pack, you repack in 5 kg (or smaller) containers or plastic bags and seal well!

Thanks guys, the co-op said they had it but didn't when I went in :/ I found another place that was selling it per kilo so I just brought a few kilos, I looked on the company website when I got home and it says "not suited for hydroponics", why would that be? I took a teaspoon or so of it and put it in a jar of water and it dissolved OK, needed a little bit of a shake but the water went clear and I can't see a white suspension or anything. Is there any other reason besides solubility that they say it isn't suited?

gmcd,

the calcium nitrate you have bought will work the same as the others. the only difference is it is wax coated granules. it is intended for soil application. the wax make sure it won't drain fast.

I strongly doubt that wax coated granules would dissolve (instantly) in water as described by gmcd. I also don't understand why they say "not suited for hydroponics". Best (and surest) is probably to ask them why. You still may get back here to check if their statement/explanation is plausible or just a conventional thing.

Btw: do not mix Calcium Nitrate (salt or concentrate) with any sulfates or some other components. When making nutrients don't forget/remember the A&B component principle.

Not instantly, it did need a bit of a shake. My cynical mind says it maybe because the sell a more expensive higher grade calcium nitrate specifically for hydroponic use, no one sells it in my country.

Its this stuff (pdf file) - Tropi-Cote http://www.growforce.com.au/Agricultural/Soluble_Fertilisers/Yara_Fertilisers/YaraCalciumNitrateNitrabor.pdf

Here is a link that might be useful: Calcium Nitrate

gmcd,

ah... i am using the same.
http://www.yara.us/fertilizer/products/yaraliva/index.aspx

'wax' is not the right word... maybe 'resin'?

the resin make sure it won't drain fast when use in soil. i use this to fertilize my soil based crop.

regarding supplies, have you look at this page? http://www.home.aone.net.au/~hydroponics/supplies.html

Here is a link that might be useful: chemical supplies in australia

Thanks kuyaig, I don't actually live in Australia, that is just a pdf file I came across. Good to know someone else is using it for hydroponics and having no problems, I really don't want to pay 10x the price and go to a chemistry supplier.