Moisture measurement, hydrated

Application to Moisture Measurement with Hydrated Aluminum Oxide Films... 

Drainage tests and initial measurements should not be made before 28 days have elapsed after the anodes are embedded in the artificial concrete system in order to allow the hydration of the concrete and to ensure moisture equilibrium, which can affect the potentials. The protection current density is limited to 20 mA ra"-(at the steel surface) to avoid possible reduction in the steel-concrete bond. Usual current densities lie in the range 1 to 15 mA 129-33]. 

The slow rate of hydration for buried surfaces is desirable from a service point of view, but makes the study and evaluation of the durability of surface treatments difficult unless wedge tests (ASTM D3762) or similar tests are used to accelerate the degradation. As for the wedge test, the stress at the crack tip, together with the presence of moisture at the tip, make this a more severe test than soaked lap shear specimens or similar types and therefore a better measure of relative durability. 

Water can be identified from its physical properties. Also, trace amounts of water may be determined by Karl-Fischer analysis. The Karl-Fisher reagent is a solution of iodine, sulfur dioxide and pyridine in methanol or methyl cel-losolve. Water of crystallization in hydrates can be measured by TGA and DTA methods. The presence of trace moisture in gases can be determined by mass spectrometry. The characteristic mass ion is 18. 

Hydrated Zeolites. The zeolitic pellets are hydrated by equilibration at atmospheric moisture content. The cell is immersed in liquid air, and a minimum equilibrium temperature of — 120°C was obtained. At that temperature the conductivity and capacity of the samples are measured over the frequency range 200-107 Hz. After eliminating the cooling liquid, the temperature rises slowly (0.5°C/min). Measurements are performed continuously in the same frequency range during the. temperature rise up to room temperature. The results are near-equilibrium values, and the errors are assumed to be the same over the complete temperature range. The same procedure was applied by Mamy for dielectric measurements on montmorillonite 11). 

Moisture in coal takes three forms (l)free or adherent moisture, essentially surface water (2) physically bound or inherent moisture (thai moisture held by vapor pressure and other physical processes) and (3) chemically bound water (water of hydration or combined" water). The ASTM defines total moisture as a loss in weight in an air atmosphere under rigidly controlled conditions of temperature, time, and air flow. Total moisture represents a measurement of all water not chemically combined. Total moisture is determined by a two-slep procedure, involving air-drying for removal of surface moisture from the gross sample, division and reduction of Ihc gross sample, and determination of residual moisture in the prepared sample. An algebraic calculation is used to obtain the total moisture value. 

Sensing chemical species is a much more difficult task than the measurement of mechanical variables such as pressure, temperature, and flow, because in addition to requirements of accuracy, stability, and sensitivity, there is the requirement of specificity. In the search for chemically-specific interactions that an serve as the basis for a chemical sensor, investigators should be aware of a variety of possible sensor structures and transduction principles. This paper adresses one such structure, the charge-flow transistor, and its associated transductive principle, measurement of electrical surface impedance. The basic device and measurement are explained, and are then illustrated with data from moisture sensors based on thin films of hydrated aluminum oxide. Application of the technique to other sensing problems is discussed. 

The various forms of moisture in coal are described according to the manner in which they are measured by some prescribed standard method. These forms are (1) inherent moisture, (2) surface or free moisture, (3) total moisture, (4) air-dry loss moisture, (5) residual moisture, (6) as-received moisture, (7) decomposition moisture, and (8) water of hydration of mineral matter. 

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. 

Despite the well-known clinical coupling of dry skin and itch, studies to objectively compare the degree of skin hydration or measurements of the transepidermal water losses with severity of pruritus have provided conflicting results on this close association. This review will discuss the existing data, breakdown the pathophysiology of xerotic itch, and describe the role of moisturizers in alleviating both entities. 

Serup, J. A three-hour test for rapid comparison of effects of moisturizers and active constituents (urea). Measurement of hydration, scaling and skin surface lipidization by noninvasive techniques. Acta Derm. Venereol. (Stockh.) 1992 177 (Suppl.) 29-33. 

Interactions of the pastes with the skin in vivo all in vivo measurements were conducted in a climatized room under standardized temperature and humidity conditions (22°C, 45 5% rh). Six healthy volunteers participated in the study. In the first part, after measurement of skin hydration with the NOVA DPM 9003,11 the pastes were randomly applied at a rate of 10 mg/cm2 on different areas (2x2 cm including one untreated control area) of the ventral forearms for 5, 30, and 120 min. Thereafter, the pastes were removed with a soft paper tissue and skin hydration was measured at 1, 2, 3, 4, 5, and 15 min. The second part of this study was conducted on the same volunteers following exactly the same procedures, but the skin was preliminary hydrated by an occlusive application of a moisturizer (an O/W lotion containing 5% urea and 10% glycerol) for 1 h. This was intended to mimic a clinical situation where the pastes are applied on wet skin states with the explicit goal of drying the skin. 

Generally when we think about measuring skin moisture we think of lotions where there is both an immediate and sustained positive increase in the hydration state after application. Classic methodologies for evaluating moisturizer efficacy start with dry skin and monitor the improvement benefit of continued product application over days or weeks.39 41 Even in short-term trials, the lotion effect on skin is typically measured as increase in moisture and the improvement in moisture-related benefits such as smoothness and elasticity.42... 

Moisturization in skin can be measured in a variety of ways, some of the more common of which are summarized in Table 31.3. It can be measured directly as an increase in hydration in skin or improvement in clinical and sensory symptoms resulting from the improved hydration state of skin. At the most basic level, consumer perceptions can provide a measure of skin feel and appearance but more often are used to quantify the sensory aspects that cannot be measured instrumentally.45 Expert clinical grading provides a more refined quantitative measure of appearance 46 The human eye is still the most powerful tool for discriminating subtle changes in appearance 47 However, bioinstrumentation is required to measure insensible parameters such as the hydration level in skin.48-50 While methods based on electrical properties of skin are widely used to indirectly measure water content, Near-Infra Red and Raman Spectroscopic techniques are more closely reflective of the actual hydration state.51,52... 

Within all of these procedures, the actual measurements continue to focus on mildness and moisturization as defined by the same three aspects used in short-term tests, sensory, visible appearance, and hydration state, with the addition of a measure of barrier integrity using TEWL. 

With regular cleansers, a procedure like FCAT (Forearm Controlled Application Test) provides good sensitivity to varying discriminate products based on their drying potential. Looking at soap versus syndet bar, we can compare three clear trends in Figure 31.13 an increase in the visible appearance of dry skin over time, a concomitant decrease in the equilibrium hydration state of the skin, and an increase in the disruption to the moisture barrier evidenced as an increase in TEWL. In all the three measures, the syndet is seen as milder and less drying. 

The ability of cleansers to positively affect the moisturization of skin can further be measured by evaluating biomechanical properties that are intrinsically linked to hydration state. For example, changes in skin softness are directly related to hydration state, and Figure 31.16 shows how biomechanical... 

---