Moisture tests

Water Activity. The rates of chemical reactions as well as microbial and en2yme activities related to food deterioration have been linked to the activity of water (qv) in food. Water activity, at any selected temperature, can be measured by determining the equiUbrium relative humidity surrounding the food. This water activity is different from the moisture content of the food as measured by standard moisture tests (4). 

A typical profile of the pressure potential of soil moisture tested by a tensometer across the free-water surface shows a negative pressure (lower than atmosphere pressure) in the capillary zone (Figure 18.2). The negative pressure in the capillary zone indicates that the capillary zone belongs to the unsaturated zone. 

Synthesis of CHDM/BA and CHDM/PDA Polyester Resins Described in Tables III and IV. CHDM, brassylic acid (or dodecandioic acid) and "Fascat 4100 in a mol ratio of 2/1/0.005 and 5 wt % of xylene were placed in a three-necked, 250-mL round-bottomed flask fitted with line, a thermometer, an Ace temperature controller, a heating mantle, a mechanical stirrer, a steam-heated Allihn partial condenser with a xylene-filled Barrett moisture test receiver below the Allihn condenser and a total condenser above it. The mixture was heated to about 140 without stirring to melt the reactants and stirring was started. Heating was continued to 205 C. A slow N sweep was maintained throughout the reaction. About 95 to 100% of the theoretical water was collected in the Barrett receiver. Upon cooling the reaction mixtures partially solidified to white waxy solids which liquified when heated to about 40 C. Acid numbers were < 1 mg of KOH/g of resin. 

Reprise cTbumiditi, Essai (Taking up Moisture Test). A French Humidity Test described by L. Medard, MP 33, 325-27(1951)... 

Hygroscopicity (or Humidity) Test (Absorption of Moisture Test) (Reprise d humidite, Essai, in Fr)... 

In vacuum oven methods for moisture determination, such as the official method of the Association of Official Analytical Chemists, lactose solutions are dried at about 100°C for 2 to 6 hr. The result in the dried product is amorphous lactose glass. Since lactose glass is very hygroscopic, the dried sample must be protected from moisture until final weighing. If a-hydrate crystals are present in the product to be analyzed, the sample is diluted with water to dissolve the crystals, since slow removal of the water of crystallization under the temperature and vacuum conditions of the moisture test unduly prolongs the moisture determination. 

Hygrascapicity (ar Humidity) Test (Absorption of Moisture Test) (Reprise d humidite, Essai, in Fr) (Hygroskopizitat- or Feuchtigkeit Probe, in Ger). The hygr nature or property of a material to absorb moisture from its environment must be known if an expl is to be considered for military or commercial use. Absorption of moisture can have an adverse effect on the sensitivity, stability, or reactivity of expls. This property should be negligible to very low absorption for most expls... 

Moisture assessment Drying endpoint target (moisture test) Granule size Sieve analysis... 

Encapsulation assessment Appearance target (moisture test) and drying cycle Visual-performed measurement of drying cycle Blend uniformity Tools available for online... 

Gross moisture sample sample representing one lot of coal and composed of a number of increments on which neither reduction nor division has been performed or a subsample for moisture testing taken. 

Bosisio, R.G., Huy, H.H. 1976. On a method of correcting for basis weight variations in dielectric moisture tests on paper, butter fats and grease samples. J. Microwave Power 12, 309-317. 

Sample Description Moisture Test Length Fines... 

Testing of encapsulated devices was done by thermal cycling and by accelerated moisture testing at elevated temperatures, high humidity and bias ( ). 

Highly accelerated moisture tests (HAST) were performed in a two-zone Hirayama pressure chamber in which samples were exposed to 145°C, 85% R.H. and 18V bias. Periodically, the devices were removed from the pressure chamber and the linear devices were tested for electrical performance in a Gen Rad 1731M Linear IC Test System. This instrument monitors several device parameters. All of these parameters remained within specifications until the devices failed due to open circuitry resulting from corrosion. Earlier tests were performed at 131°C, 85% R.H. and 30V bias (2). Under these conditions the test requires long times. Short test times are readily achieved at 145°C (6). 

Table V. Accelerated Moisture Testing of Linear Devices at 145°C/85%RH/18V...

In addition to the linear devices, accelerated moisture tests under identical conditions were also performed on the digital devices on A-42 leadframes. The results are given in Table VI. 

Figure 6.26 Typical drawing of bottle finish Table 6.2 Results of moisture tests...

Electrical properties of grain have been utilized for quick moisture tests based on the measurement of resistance, capacitance, or electrical conductivity. Many studies have been devoted to the development of density-independent functions of the dielectric properties that would permit on-line measurement of moisture content [74-76]. Also, measurements of electrical properties of grain and seed have been employed for purposes other than determining moisture content. For example, viable seeds of corn were sorted from dead seeds by measuring the current conducted by individual soaked kernels between electrodes connected to a 6-V dc source [77]. Another application of electrical properties is electrostatic separation where the ability of a seed to hold a surface charge is determined mainly by its conductivity. 

The water content or moisture test for aggregates is determined by drying them in a ventilation oven at 110°C 5°C. 

Figure 2 Vacuum pump, Pirani vacuum gauge, and hygrometer in low-humidity room for gravimetric moisture test. 

Figure 3 Desiccator in desiccator guard and sulfuric acid scrubbers to remove water from air used to release vacuum in desiccator in gravimetric moisture test.

Figure 4 Dry box with sample vials, weighing bottles, hygrometer, and Petri dishes filled with anhydrous phosphorus pentoxide for sample preparation for gravimetric moisture test.

One of the most useful tests for various plasties and additives is a moisture test. Often the moisture content is a eritieal measurement for plastics products. Lack of moisture control can cost a business significantly in out-of-specification product, downtime, and raw materials. Alternatively, effective moisture eontrol can save a company thousands of dollars. 

In 2009, the ASTM International Committee D02 on Petroleum Products and Lubricants has approved a new ASTM method which covers the determination of moisture content in new and in-service lubricants and additives by relative humidity sensor. The method, D7546 - 09 Standard Test Method for Determination of Moisture in New and In-Service Lubricating Oils and Additives by Relative Humidity Sensor, offers users an alternative to moisture testing by Karl Fischer titration. 

FIGURE 10.12 Percent weight change after a five-day ambient moisture test and 125 C bake. 

---