Mixing baking soda, or NaHCO3, with hydrochloric acid, or HCl, results in table salt, NaCl, as well as water, H2O, and carbon dioxide, CO2. These experiments can also demonstrate stoichiometry, which deals with the reactants and products in chemical reactions.

This is an acid-base reaction (neutralization): NaHCO 3 is a base, HCl is an acid. This is a gas evolution reaction, CO 2 is the formed gas. , [Note: Often used in an aqueous solution.]

Ca(OH)2 we used is new, and saturated Ca(OH)2 solution is high. I can use the saturated Ca(OH)2 solution to change the PH level of CaCl2. 6H2O solution up to 9 or 10, but it will serious decrease its latent heat.

Soil pH is commonly measured in water or 0.01 M CaC12. Soil pH in CaCl2 is usually preferred as it is less affected by soil electrolyte concentration and provides a more consistent measurement. However, the pH difference between measurements in water and CaCl2 is related to the soil solution electrolyte concentration.

Soils have the capacity to resist changes in pH, but there are instances where the water pH can cause changes. Both the soil and the water contain negatively and positively charged ions that influence the chemical composition and thus the pH of soil.

pH measurements are determined in both water and a calcium chloride solution because the calcium displaces some of the exchangeable aluminum. The low ionic strength counters the dilution effect on the exchange equilibrium by setting the salt concentration of the solution closer to that expected in the soil solution.

Pure distilled water should be neutral with a pH of 7, but because it absorbs carbon dioxide from the atmosphere, it’s actually slightly acidic with a pH of 5.8.

It is generally accepted that the pH(KCl) of a soil is a good indicator of soil acidity. The pH(KCl) value is when a diluted solution of potassium chloride (KCl) is used in the analysis, instead of water (H2O) which gives the pH(H2O) value. If a soil has a pH(KCl) of less than 4,8 it can be regarded as being acidic.

pH is determined by measuring the hydrogen ion activity in an aqueous solution. A glass electrode, calibrated against a pH standard is used to do this. A sub-sample of soil is mixed with water or CaCl2 at a ratio of 1 part soil to 5 parts liquid and the pH of the suspension is measured after 1 hours shaking.

Testing pH Using Soil Strips

1. Dig for a Sample.
2. Place 1 to 3 Teaspoons of Soil in a Clean Glass.
3. Pour in Distilled Water.
4. Agitate the Soil Vigorously by Stirring or Swirling.
5. Pour Soil Sample Through a Coffee Filter and Into Another Clean Glass.
6. Dip the pH Test Strip into the Liquid.
7. Repeat the Process.

Two materials commonly used for lowering the soil pH are aluminum sulfate and sulfur. These can be found at a garden supply center. Aluminum sulfate will change the soil pH instantly because the aluminum produces the acidity as soon as it dissolves in the soil.

Cation exchange capacity

Factors influencing the CEC include the soil type, the soil pH and the soil organic matter content. Soils are made up of sand, organic matter, silt and clay particles. Soils with high sand content have low holding capacity for cations compared to clayey and silty soils.

To determine the cation exchange capacity (CEC), calculate the milliequivalents of H, K, Mg, and Ca per 100g of soil (meq/100g soil) by using the following formulas: H, meq/100g soil = 8 (8.00 – buffer pH) K, meq/100g soil = lbs/acre extracted K ÷ 782. Mg, meq/100g soil = lbs/acre extracted Mg ÷ 240.

Soils with a higher clay fraction tend to have a higher CEC. Organic matter has a very high CEC. Sandy soils rely heavily on the high CEC of organic matter for the retention of nutrients in the topsoil.

Defining Cation Exchange Capacity The total number of cations a soil can hold–or its total negative charge–is the soil’s cation exchange capacity. The higher the CEC, the higher the negative charge and the more cations that can be held. CEC is measured in millequivalents per 100 grams of soil (meq/100g).

Soil cation exchange capacity (CEC) is a significant number for an important soil characteristic. If the CEC number is low, not many molecules are able to bind (react) to the particle surface. If the number is high, a larger number of molecules can bind to the particle’s surface.

Clays such as kaolinite have a CEC of about 10 meq/100 g, while illite and smectite have CECs ranging from 25 to 100 meq/100 g. Organic matter has a very high CEC, ranging from 250 to 400 meq/100 g.