Quote:
Originally posted by Fishaholic
Pickling Lime and Kalkwasser are the same exact thing minus the nice label and fancy german name.
|
Essentially this is true, although based on the initial grade of the limestone that is used to make the Calcium oxide it may differ...
Quote:
|
It is mixed at th same rate as it is the same thing, 2 tablespoons per gallon... ...I also mix it first in 20 ml of white vinager (acetic acid)...
|
Mixing direction rate is correct, but using Vinegar defeats the purpose of using Ca(OH)2 to start with. You end up with a solution of Ca acetate (very soluble) and water, instead of Calcium carbonate/bicarbonate (relatively insoluble) ions ... this will initially drop pH and will not help to maintain buffer capacity nearly as well as saturating a solution with Calcium oxide/ calcium hydroxide to provide for the buffering effect from the carbonate/bicarbonate ions. Although 20 ml of vinegar is not enough to completely neutralize the buffer present, it will prevent it's initial formation, as acetate ion is an organic acid, and the protons they donate to the solution will actually neutralize some of the existing buffer capacity of the system. Buffer will come back up somewhat, but the addition of acetic acid in the form of vinegar is totally unnecessary, even detrimental in view of what our expected outcome should be.
Quote:
|
...Both Pickling Lime and Kalkwasser are not batched, they are mined and both at the same purity, some claim Kalkwasser is a higher grade but it does not prove to be...
|
I'm not sure what you mean by "batched", but these products are made in "batches" and have lot numbers for the batches in which they are produced. Kalk and pickling lime are both mixtures of (very little) Calcium Oxide ( CaO ) and (mostly) Calcium Hydroxide ( Ca(OH)2 ). They are mined only in the sense that the raw precursor to make these products is mined Calcium Carbonate, either as marble that is not suitable for construction or deposits of Chalk or high purity limestone.
The products we seek are made first through the production of Calcium Oxide, then the manufacture of a more stable Calcium Hydroxide. Calcium Oxide is made by calcining a relatively pure native calcium carbonate, e.g., marble chips, chalk or limestone in a suitable kiln where the carbonate will be removed as carbon dioxide, leaving behind CaO. This kiln is usually a vertical cylinder of either steel or masonry lined with firebrick, heated by a boxed heat source (usually gas-fired) near the base of the kiln. The kiln is arraigned so that the entire mass of the limestone is exposed to the combustion products of the furnace without coming into actual contact with the flame. Large amounts of lime can be cheaply made in this manner using rotary furnaces. I might point out that this is also one of the sources of reef destruction in the South Pacific. Reefs are mined for their limestone (skeletons) to supply lime used for road and related structure construction.
Native Calcium Carbonates contain varying amounts of impurities, usually oxides and carbonates of magnesium, iron, silica, and varying clays. The final grade of the lime is determined by assay of the final product, and may vary from Pharmaceutical to construction grade. If there is enough of the clay present, the final product is called "over-burnt lime" and is used to make a quicklime product that is suitable only for construction/mortar purposes. The Calcium Oxide is the precursor for the production of Calcium Hydroxide, also known as "slaked lime", so called because it is thirsty for water (I will explain).
Also called "hydrated lime", Calcium Hydroxide is made by the careful addition of a limited amount of water to lime (Calcium Oxide). This process is known as "slaking" and is characterized by the avid absorption of water by the oxide to form Calcium Hydroxide in an extremely exothermic reaction.
Calcium hydroxide solutions are basic by reaction with water (pH of the saturated solution at room temp is 12.3) with a solubility of 1 gm in 630 ml of water at 25C. Solubility goes down as temp goes up (greater reactivity results in more precipitate, remember, solution for this product is
exothermic) to around 1 gm in 1300 ml water at 100C. Freshly made solutions of this substance will be clear, but will turn cloudy as they absorb carbon dioxide from the atmosphere to form Calcium Carbonate. This is not the initial precipitate seen when mixing the solution, that is from the excess Ca(OH)2. Allow this to settle out, and you can use the supernatant liquid (the clear liquid above the precipitate layer). Store this solution in a tightly close container, and to dose it, use a closed collapsible container to prevent the introduction of CO2.
If you want to test the purity of the lime that you have, I have the assay tests for Ca(OH)2 for those of you that might be interested, or you can contact the USP on the Internet for the assay standards.
Heh, just my $0.02 US ... Hope this clears up any misconception on this product. Although the pickling lime may not be pharmaceutical grade, it supplies the things we want without supplying an unacceptable level of contaminates (food grade is almost pharmaceutical grade)
Mrs. Wages costs me $1.19 per lb. at Kroger!
