Gravimetric technique

Classical wet chemical methods and instmmental techniques are used for the analysis of soluble sibcates (91). Sibca is deterrnined by gravimetric techniques or by the fluorosibcate volumetric procedure. 

The main advantage of the gravimetric technique is that it requires a much smaller sample than the stoichiometric technique. In many cases, samples as small as 70 mg are sufficient. Accurate temperature and pressure control and measurement are still required, but gas adsorption on the metal walls of the equipment is no longer a concern because it is only the weight gain of the sample that is measured. 

Styrene conversion calculated by this equation and styrene conversion obtained for runs 12-15 by gravimetric methods were in good agreement. In general, the gravimetric technique was 1 to 5% points greater than conversions calculated using the GPC data. 

Acoustic perturbation methods, 14 617 Acoustic streaming, 9 59, 81 Acoustic wave gravimetric technique, acoustic wave sensors and, 22 270. 

Gravimetric methods, tellurium determination by, 24 415 Gravimetric techniques. See also Acoustic wave gravimetric technique for anthropogenic silicas and silicates, 22 470... 

ISO 6179, Rubber, vulcanized or thermoplastic - Rubber sheets and rubber-coated fabrics - Determination of transmission rate of volatile liquids (gravimetric technique), 1998. 

Gravimetric techniques are broadly based upon the quantitative precipitation of the respective cation or anion from a given solution in two different ways ... 

Troya, M.T. and Navarette, A. (1994). Study of the degradation of retified wood through ultrasonic and gravimetric techniques. International Research Group on Wood Preservation, Doc. No. IRG/ WP 94-40030. 

ISO 1663 1999 Rigid cellular plastics - Determination of water vapour transmission properties ISO 2556 1974 Plastics - Determination of the gas transmission rate of films and thin sheets under atmospheric pressure - Manometric method ISO 6179 1998 Rubber, vulcanized or thermoplastic - Rubber sheets and rubber-coated fabrics - Determination of transmission rate of volatile liquids (gravimetric technique)... 

Various procedures have been reported in literature to investigate the sol-ubihty of compoimds in SCCO2 [34], They can be divided into static [34, 35] and dynamic [36,37] methods. Most recently, also parallel techniques have been developed for solubility measurements [38]. All methods, except for the static synthetic one (see below), require analytical measurements to quantify the amount of solute dissolved in SCCO2. Mainly spectroscopic, chromatographic, and gravimetric techniques are applied for the analytical measurements. 

The application of SFE for the preparation of samples in the analytical laboratory has received serious attention as a sample preparation step for extracting analytes of interest from a bulk matrix prior to their determination by other analytical methods including chromatographic, spectro-metric, radiochemical, and gravimetric techniques. 

The method most widely used to determine gas solubilities in ILs is gravimetric. As we first showed in 2001 [11] gravimetric techniques are unique, suited to measure the solubility of gases and vapors in ILs because the liquid does not evaporate into the vapor, complicating the measurements. Thus, apparatuses designed to measure gas sorption on solids can be used readily for ILs. 

Other gravimetric techniques include flowing a mixture of carrier gas and adsorbate through a tube packed with adsorbent. Stopcocks at each end of the tube permit isolation of the sample. The tube is then removed from the flow stream and weighed. Two successive equal weights indicate the equilibrium is achieved. The quantity adsorbed must be corrected for the gas contained in the void volume. 

Adsorption-desorption techniques are often used for the study of surface treatment or modeUng of polymer/filler interaction. Gravimetric techniques or. 

The sorption of butanol isomers (303 K) enables us to further investigate the sorption characteristics of the phenyl-modified silica.. The adsorption isotherms presented here were measured using a gravimetric technique and are compared with previously reported nitrogen, water and benzene sorption data.3... 

The choice of which protocol to use will depend on what type of matrix is being tested. As a first suggestion, Table Al. 1.1 is provided based on the matrices and methodologies currently recognized by the AOAC (Sullivan and Carpenter, 1993). As one can see, many matrices can be run by more than one gravimetric technique. The method used will depend on the matrix or on the end use of the dried sample. For a general review of all methods, Karmas (1980) has written an evaluation with emphasis on food matrices. 

We have also compared the determination of the adsorption isotherms with those from a standard gravimetric technique. The precision of the data obtained by the gravimetric technique was found to be lower than that obtained by the FT-IR technique, particularly at very low silane concentrations (about 5%, and 3% at 0.4 g/100 ml concentration for the gravimetric and the FT-IR techniques, respectively). This is because very small weights of the silanes cannot be measured accurately and the silane is volatile. The effects of suspended silica particles in the solution were also examined by centrifuging methanol solutions... 

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