Queston for Randy about Calcium Oxide v Hydroxide

[CleveYank]

Stumbled across Calcium Oxide or Kalkwasser plus by Warner Marine being dosed in TOTM Dec 2003.
http://reefkeeping.com/issues/2003-12/totm/index.php

It's noting is brief with no information as to why the selection. Will probably PM mojoreef for his exact reason. But in the meantime inquiring here with the chemistry applied users.

Googling only pulls up vast hits for Calcium Hydroxide which I know about as much as you need for usage benefits and cons in a reef system.

This related animal less the hydrogen, of Calcium Oxide not so sure.

Randy or others who know, what's the beneficial differences or reason one would want to use a kalkwasser made from Calcium Oxide (Quick lime) insteaded of dosing the tried and true Calcium Hydroxide standard adopted Kalkwasser mixture?

And of course what negatives of dosing the Calcium Oxide are there if any?

 

[Randy Holmes-Farley]

Both work equally well. The oxide just has less water in it to start with. I used the oxide for years and now use the hydroxide just because that's what was available.

 

[CleveYank]

With the difference of with hydrogen or without there is no different positive or negative factors between the two as applied to being used as a kalkwasser solution? They are identical in all ways as to how they impact a reef system?

 

[bertoni]

Yes, they convert to the same form when added to saltwater. The calcium oxide releases a lot more heat, though, which can be an issue in some situations.

 

[Randy Holmes-Farley]

It is not hydrogen per se, just water:

calcium oxide (CaO) + water (H2O) = calcium hydroxide (Ca(OH)2

That happens almost instantly on contact with the water and is what causes the heat that Jonathan mentions.

I discuss it here:

What Your Grandmother Never Told You About Lime
http://reefkeeping.com/issues/2005-01/rhf/index.htm

specifically here:

What Is Lime?

According to the National Lime Association, “lime” is defined as either quicklime or hydrated lime. These materials are made by heating calcium carbonate until the carbon dioxide is driven off, forming quicklime (calcium oxide):

1. CaCO3 --> CaO + CO2

Water can then be added to form hydrated lime (calcium hydroxide; referred to subsequently in this article as just lime):

2. CaO + H2O --> Ca(OH)2

Both lime and quicklime are suitable for making limewater (kalkwasser) and otherwise supplementing calcium and alkalinity in reef aquaria. There are some important differences between the use of lime and quicklime that will be discussed in subsequent sections. These differences relate to the fact that quicklime is slightly more potent and gets hot when water is added to it (equation 2).

A couple of other definitions are worth noting. Limewater is the solution that forms when lime (or quicklime) dissolves in fresh water. The solution is exactly the same using lime or quicklime, as long as the same amount of calcium is added. Kalkwasser is simply the German word for limewater. Neither term is ever correctly applied to a solid, so any solid material sold as “kalkwasser” is either lime or quicklime.

Pickling lime is, in most cases, food grade calcium hydroxide. Mrs. Wages website (a place to buy pickling lime online) refers to it as calcium oxide in some places, but my understanding is that this product is calcium hydroxide. [As an aside, some of Mrs. Wages other information about pickling lime makes no sense at all, such as saying the reason that it contains lime is proprietary, but in the line above, showing how it works.]