how to reduce water content in a chemical?

Question

how to reduce water content in a chemical, says, initially 3% water content reduce to 0.1%.

if you suggest vaccum the container, please tell me why vacuum would reduce the water content?

Answer 1

The exact technique used to remove water is going to depend on what the physical state of the "chemical" you're talking about is as well what its specific identity is. Without knowing those things it's impossible to answer the question except in very general terms.

For inorganic solids, it is often possible to reduce water content by holding the material under high vacuum with or without the application of heat. This works because water is going to have a very high vapor pressure relative to something like an inorganic salt and will be drawn off by the vacuum. This is not appropriate for materials that sublime easily or are potentially heat sensitive.

Organic solids can be dissolved in a solvent and the treated with a drying agent like MgSO4, molecular sieves, etc. The solvent can then be removed under vacuum and the last traces removed under high vacuum.

Organic liquids may be treated similarly to organic solids, or they can be treated directly with the dying agent and then separated by filtration or distillation.

Gases can be dried by passing through drying agents or by fractional freezing (i.e. freeze the water out) or distillation.

The specific choices involved in any one of those methods is going to be dependent on what "chemical" you're talking about. This is definitely not a one size fits all kind of thing.

Answer 2

Water is a real bummer isn't it.

Use a Rotovap - a round bottom flask is tilted at 45 degrees and spun. It is attached to a gentle vaccum.

As the flask rotates, the liquid - in this case, water - coats the sides increasing the surface area available for evaporation.

(alternatively, swirl whatever container your solution is in)

The gentle vaccum creates lower air pressure which speeds up the evaporation.

Voila. You should have product sooner. However, water is still a pain.

I like the suggestions about washing in organic solvents like ether or acetone - just make sure you don't let them react with your product. AND, if you rinse with ether, then you a separation funnel, you want to be sure which layer your product is in! It's just that organic solvents evaporate so much faster.

Answer 3

Chemical Oxygen Demand (COD) is a measure of the extent of reactivity of reduced species still present in the water. You have not provided sufficient oxidation in the treatment process to cause the oxidation of these various reduced compounds, so there are still residuals present. These compounds will continue to react when presented with oxidizing constituents in the natural environment. You need to hit the effluent harder with your oxidation step (increase the amount of oxidizer) before discharge, or possibly provide a longer residence time if the situation is simply a result of inadequate time to consume all of those constituents even though you have provided an excess of reactive oxidizer. Sometimes a better filtration upstream from the chemical treatment can help by removing organic particulates that consume your oxidizer (make the oxidation step attack the dissolved constituents rather than the suspended particulates). How you proceed depends on what is going on.

Answer 4

boil it. I'm not guaranteeing that your chemical wont explode... It should work, water evaporates faster when the temperature goes up. Hopefully your chemical doesn't evaporate too! You might want to do research if you were planning to attempt this....

Answer 5

Moisture content can be eliminated or reduced by aeration. Maybe a dessicator can help.

Answer 6

You could let it sit in some dehydrated salts, like magnesium sulphate, i think.
Or you could rinse it in ether several times,or acetone.

Answer 7

increase the heat so the water can b evapourated

Answer 8

Try a desiccator.