Sampling moisture loss

Since Ppore depends heavily on vapor pressure, this is expected to occur after some cooling takes place. As Ppore decreases and vapor condenses, the pressure difference is expected to force the oil within the structure. The condensation mechanism should predominate in thick samples and short frying times, since in thinner samples or longer frying times, moisture loss rate may diminish considerably (and therefore Pp0re)> allowing oil absorption to begin early. 

Some workers use 20 g air-dry soil, add 12 ml water and incubate in the dark at 22°C for 28 days, making good any moisture loss. Others extract the air-dry soil directly. The given method uses the fresh (or thawed) soil sample. The usual extractant for moist soils is 2 M KCI, but for dry soil, 10% m/v KCI (1.34 M) may be used. The amount of nitrite-N in the soil is usually so small that it can be neglected, but it will be incorporated in the amount of nitrate recorded. 

Place sample (5 to 10 ml) in a disposable sample cup, completely covering the bottom of the cup, if possible. Place sample into sample cup in a timely manner to minimize moisture loss or gain during handling. If sample is not to be tested immediately, place a sample cup lid on the cup to prevent moisture transfer with the room atmosphere. 

Fill a sample cup half full ( 7 ml) with selected salt standard. Place sample into sample cup in a timely manner to minimize moisture loss or gain during handling. 

Drip losses, cooking/processing loss, and thaw loss are related to, but different from, expressible moisture. In these measurements, the moisture loss that is measured is the amount lost without the application of any force. Thus, the liquid that is expelled can be collected by carefully pouring off the excess liquid. Placing the food sample in a funnel and collecting the drip in a graduated cylinder is often the easiest way to practically accomplish this task. 

Expressible moisture (EM) measures the water that can be squeezed out of a material, generally under a force. Traditionally, the Carver press was used with meats (Forbes et al., 1974 Lee and Patel, 1984). A piece of meat was placed between large pieces of filter paper. The press squeezed out the moisture, and the investigator measured the diameter of the wet circle on the filter paper. One of the problems with the Carver press method is ensuring the use of consistent pressure each time. Also, one can only measure a single sample at a time. Because of the arbitrariness of the conditions, the exact relationship to a real sample is not known. The actual amount of moisture loss is also not determined. 

Usually, the first moisture value to be obtained on a coal sample is the air-dry loss moisture. This moisture loss occurs during an attempt to bring the coal sample into equilibrium with the atmosphere in the sample preparation room. The practice of using temperatures above room temperature may accelerate oxidation but shortens the time needed for air drying hence, temperatures above 40 to 50°C (104 to 122°F) are not recommended for air drying. 

Variations in the data that fall outside the experimental allowable limits may be due to factors that originate during sample preparation and handling, such as (1) the sample moisture may not have been in equilibrium with the laboratory atmosphere (2) the sample may have been overdried or under-air-dried (3) excessive dust loss may have occurred during screening due to a loose-fitting... 

Moisture total moisture content of a sample customarily determined by adding the moisture loss obtained when air drying the sample and the measured moisture content of the dried sample. Moisture does not represent all of the water present in coal, as water of decomposition (combined water) and hydration are not given off under standardized test conditions. 

A convenient way to quantify the Increase In magnitude of the u transition with the Increase In epoxy moisture content Is to compare the area under this transition peak with sample moisture content. Several possible dynamic mechanical property comparisons exist. No Identifiable trends were observed between the magnitude or area of the loss modulus (E") or tan d and the amount of moisture In the N-5208 or DGEBA-TETA epoxy samples. 

Vn>en the area under the Log (S") versus temperature curve Is plotted against epoxy moisture content, there Is a definite Increase with Increased moisture content. One method for presentation of the data Is to simply plot the area under the loss compliance transition as a function of sample moisture content. This could be done for each epoxy under consideration. 

---