Samples pressure pans

C 0.5 M HCl solution and mixes this reaction mixture further °C over the time of 1 h at the same temperature. The reaction mixture further held at room temperature for 24 h, filtered, washed off by 250 cm of distilled water to neutral value of pH and dried in the vacuum drier under the 60 1°C and under pressure 0.9 0.05 kg-cm. Preparation conditions of synthesized samples of PAn and composites shown on Table 1. 

Volatile sample pans and crimpers Vapor pressure pans and crimpers Large-volume stainless steel pans and crimpers Reusable high-pressure capsules and sealers Autosampler system pans and universal crimpers... 

In the case of samples taken to very high temperature or pressure, capsules which hold internal pressures up to 150 bar should be used. Disposable high-pressure capsules which avoid the need for cleaning are available. For hazard evaluation, gold-plated high-pressure pans should be used, since these should be inert towards the sample. 

Loss of solvate and hydrate are both observed as endothermic events resulting from the loss of mass from a pan in a sealed high-pressure pan no transition may be observed. The loss of moisture from a sample can therefore be a significant issue since it can obscure smaller events occurring in the same region, for example the glass transition in a polyamide or a freeze-dried material such as heparin (Figure 2.7). 

Explosives are a particular class of exothermic reaction where the size of the exotherm is very large. Using small sample sizes of 1-2 mg in the DSC allows the reaction to be controlled and measurements can be made without damage to the analyser. The DSC can be considered as a screen for hazardous materials usually high-pressure pans are used to encapsulate the sample, and a kinetic evaluation produced. If potential hazard is indicated then samples of larger size can be run on other equipment, for example isothermal/adiabatic calorimetry, to obtain more exact information. 

When weighing the filter after sampling, include any loose material from an overloaded filter and cassette. At all times take care not to exert downward pressure on the weighing pans. Such action may damage the weighing mechanism. 

The sample containers most commonly used are cylindrical pans pressed from pure aluminium foil. Alternative materials are used for very high temperatures or corrosive substances, and hermetically sealed pans to withstand several atmospheres pressure can be used for volatile materials. Some heat flux DSC instruments are available which are capable of operation at high pressures, by means of containment of the DSC cell within a pressure vessel. 

The GPC instrumentation and GPC procedures used here are the same as described earlier (I) but with slight alterations. The Kroeger HAK-1 pads furnished with the pressure filter were replaced by Millipore 5-/x Mitex membranes to reduce changes in solution concentrations arising from adsorption of the solute on the fibrous material of the pad. When retention of eluted fractions was desired, two shallow aluminum pans filled with tetrahydrofuran (THF) were placed in the syphon box, and then the door was closed and latched. The saturation of the enclosed air space by THF vapor minimized evaporation of the solution during drop formation, drop fall, and retention of fraction in the syphon. The possibility of diluting the sample solution when charging the sample loop was... 

Different sample pans are used in DTA and DSC measurements for samples of various shapes and physical states. The sample pans are of two types open pans for solid samples and sealed pans for liquids or volatile samples. The materials used for making sample pans are mostly aluminum, silver, gold, stainless steel, and carbon. When aluminum and silver sample pans are used for samples containing water, the sample pans should be pretreated with water in a small pressure vessel to avoid reactions between the pans and water during subsequent heating. 

A study of the hydrophilic sites on the surface of activated carbon fibres has been made recently by Kaneko et al. (1995) with the aid of X-ray photoelectron spectroscopy (XPS). In this work cellulose (CEL)- and polyacrylonitrile (PAN)-based activated carbon fibres were used and samples were either chemically treated with H202 or heated in H2 at 1000°C. As expected, surface oxidation by the H202 treatment increased the initial uptake of water, while the H2 reduction caused a marked decrease in the amount of water adsorbed at low p/p°. Measurement of the peak areas of the XPS spectra provided a means of determining the fractional surface coverage by the hydrophilic sites. In this way a linear relationship was found between the low-pressure adsorption of water vapour and the number of hydrophilic sites (mainly —COOH). 

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