How to measure the calculation of irreducible water saturation

Calculate water content

Here you can have the water content calculated quickly and easily. Simply enter the fresh mass and the dry mass below.

WG = water content
TM = dry matter
FM = fresh mass

Calculate water content

The determination of the water content is one of the basic tests on leather, food, soil or wood, for example, since the water content has important properties. For example, dry wood has a higher resistance to the flow of electrical current than damp wood and one can indirectly deduce the wood moisture. The water content in percent is the mass of water contained in the wood divided by the total mass of the moist wood times 100. The water content is the ratio of the water content and the wet weight of the wood. One can say that the water content consists of the respective proportion of the water in percent of 100 of the total mass and is referred to as volumetric and gravimetric.

Calculation of water content

The water content indicates the amount of water that is contained in a material.

Volumetric: water volume divided by total volume times 100%

Gravimetric: water mass divided by dry mass of the material times 100% with the water content you can also get values ​​over 100 percent.

When calculating for wood, the gravimetric water content is related to the wet mass.
The air contains the water in vapor form. The amount of water is calculated as the mass of water vapor in kilograms per m3 of air, which results in absolute humidity.

The amount of water vapor per square meter of air that is absorbed when the air is saturated with water vapor is the air humidity. The warmer the air, the more water vapor it can absorb; if the air temperature drops, it condenses and fog and rain forms.

Then the saturation humidity of the respective air temperature is reached.

Example: Calculating the water content of plants
Assuming that after the plants have dried, the water has completely disappeared and you have a fresh weight of 800 grams and a dry weight of 500 grams, then the water content is calculated as follows:

Water weight = fresh weight 800 g minus dry weight 500 g results in 300 g. Water content
measure the weight beforehand and let it dry; and then the difference is the water.

There are various options and methods available to determine the water content in the soil. Oven drying or the radiometric method enables the water content to be verified using the flame method. The soil sample is dried with a flaming liquid, for example denatured alcohol. This is called the field method.

In medical examinations with image diagnostics, for example ultrasound or computer tomography, the brightness of an image point often shows how high the water content is and this provides information on the condition of soft body tissue.

What is water content?

How do you calculate the water content?

How do you measure the water content?

Why do you need the calculation of the water content?

Example for the calculation of the water content from practice

What is water content?

Water is the source of all life and therefore occurs in almost all natural raw materials and organisms. The term water content describes the proportion that water takes up in these raw materials or organisms.

A basic distinction must be made as to whether the water content is determined based on proportions by volume ("volumetric") or proportions by mass ("gravimetric"). In any case, the water content is a ratio that relates to the total amount and is therefore given in percent.

How do you calculate the water content?

Volumetric water content (theta)
= Vwater / Vtotal [%]

Gravimetric water content (omega)

w = mwater / mtotal [%]

When using both formulas, it is important that the respective data on volume or mass are available in the same units of measurement. This is the only way to determine the correct percentage of water content.

How do you measure the water content?

The brass of the water content is usually carried out in such a way that the water contained in the sample is separated by drying. To do this, the initial volume (or, in the case of the gravimetric method, the initial mass) of the sample is first determined and then dried slowly and, above all, evenly.

This is done by supplying heat, the completely dried residual sample then has a reduced volume (and a reduced mass) - the difference to the original sample is the water content. A critical aspect of this process is that other substances that evaporate more quickly, such as alcohol, are also added a reduction of the sample and thus lead to a measurement error.

An alternative method is to recapture the water that has evaporated during the drying process through condensation on a cooled surface and to make the amount of water separated in this way directly measurable. Known components that evaporate at a lower temperature can be eliminated in advance using appropriate temperature profiles. However, this method is still imprecise in that a certain amount of water remains in the air as moisture.

Why do you need the calculation of the water content?

The calculation of the water content is often used to determine a quality or product grade. The following examples are mentioned:

- The water content in fuels (often referred to as "residual moisture") is, on the one hand, an indication of how easily the fuel is flammable. The more residual moisture there is, the more difficult it is to ignite the fuel.

At the same time, fuel prices are often billed in tons. It is easy to imagine that wood with a high level of residual moisture, for example, weighs more (and is therefore more expensive per cubic meter) than completely dried wood. That is why the price is usually linked to a maximum permissible residual moisture.

- The water content in certain foods determines the shelf life of the food. Completely dry, powdery foods have a longer shelf life than the same substances if they contain water (risk of mold formation).

The measurement / calculation of the water content is therefore carried out in these cases by the manufacturer and, if necessary, also by the dealer, in order to be able to guarantee perfect quality at the time of delivery.

Example for the calculation of the water content from practice

A test quantity of 50kg lignite briquettes (extract from a delivery of several tons) should be classified for their water content upon delivery. After complete drying in a climatic cabinet, the test quantity weighs only 49kg. What was the water content on delivery?

Gravimetric water content

w = mwater / mtotal
= (mdelivery - mdry) / mdelivery
= (50 kg - 49 kg) / 50 kg
= 2%