Sodium sulfate is present in some soils. Salt easily becomes hydrated and dehydrated under the influence of climate change. Massive changes occur during this process of hydration and dehydration, which affect the engineering properties of the soil.
- Take the soil sample in a condition in which it can crumble. If necessary, put it in the oven at 105 . dry on0C to 1100C. Break the lumps in mortar with rubber covered pebbles. Mix the sample thoroughly and subdivide it by quarter.
- Take 10 g of soil from the sample in a 250 ml bottle with 100 ml of distilled water. Shake it occasionally with a mechanical shaker for about 2 hours. Let the soil stand overnight. If the soil is scattered, add 0.5 to 1.0 g of pure potassium nitrate to aerate the particles.
- Filter 25 ml in a beaker. Check whether the solution is alkaline with a phenolphthalein indicator. If so, add concentrated hydrochloric acid to neutralize the solution. To make the solution acidic, add 4 more ml of hydrochloric acid.
- Boil the solution. Remove the solution from the heat and pour the hot barium chloride solution in a fine stream, stirring constantly, until no more precipitation falls.
- Place the beaker on a steam bath for at least 4 hours and allow the precipitate to settle. In addition, precipitate, dry and ignite filtration can be done through a pre-loaded sintered glass crucible or a Gooch crucible through an ashless filter paper wash free of chloride iron. In ash condition after the filter paper has dried. The precipitate is then ignited on a burner or in a muffle furnace at 600oC to 700oC for half an hour on low flame.
- Cool in a desiccator, weigh and note the residue. This is the weight of barium sulfate.
Calculate the corresponding weight of sodium sulfate and determine its percentage as follows:
a) sulfate (SO .)4) percent by mass = 41.15 W1/w2
b) sodium sulfate (Na.)2 therefore4) percent by mass = 60.85 W1/w2
woo1 = mass in g of the precipitate
woo2 = mass of grams of soil contained in the solution taken for precipitation.
IS: 2720 (Part 27) -1977