Gravimetric filtration

Suspended Solids None Suspended Solids is the measure of undissolved matter, determined gravimetrically suspended solids plug lines, cause deposits in heat exchange equipment, boilers, etc. Subsidence, filtration, usually preceded by coagulation and settling... 

The main principles of instrument design are summarized in Table 10.23. In filtration, e.g. for gravimetric analysis, selection of filter material (Table 10.22) requires careful consideration in terms of application, strength, collection efficiency, compatibility with pump, water uptake, etc. Humidity-controlled balance rooms, iTiicrobalances and careful handling techniques may be required. 

Different test methods produce numerically different results and comparisons should only be made of results using the same test method. Tests fall into three categories gravimetric tests, which measure ability to trap and retain dust those which measure staining power of contaminants before and after filtration and those measuring the concentration of a test aerosol either side of the filter by photoelectric methods. The tests which will be met most often are as follows. 

A process for the gravimetric determination of mixtures of selenium and tellurium is also described. Selenium and tellurium occur in practice either as the impure elements or as selenides or tellurides. They may be brought into solution by mixing intimately with 2 parts of sodium carbonate and 1 part of potassium nitrate in a nickel crucible, covering with a layer of the mixture, and then heating gradually to fusion. The cold melt is extracted with water, and filtered. The elements are then determined in the filtrate. 

In electro-gravimetric analysis the element to be determined is deposited electroly tically upon a suitable electrode. Filtration is not required, and provided the experimental conditions are carefully controlled, the co-deposition of two metals can often be avoided. Although this procedure has to a large extent been superseded by potentiometric methods based upon the use of ion-selective electrodes (see Chapter 15), the method, when applicable has many advantages. The theory of the process is briefly discussed below in order to understand how and when it may be applied for a more detailed treatment see Refs 1-9. 

Precipitation reactions have many applications. One is to make compounds. The strategy is to choose starting solutions that form a precipitate of the desired insoluble compound when they are mixed. Then we can separate the insoluble compound from the reaction mixture by filtration. Another application is in chemical analysis. In qualitative analysis—the determination of the substances present in a sample—the formation of a precipitate is used to confirm the identity of certain ions. In quantitative analysis, the aim is to determine the amount of each substance or element present. In particular, in gravimetric analysis, the amount of substance present is determined by measurements of mass. In this application, an insoluble compound is precipitated, the precipitate is filtered off and weighed, and from its mass the amount of a substance in one of the original solutions is calculated (Fig. 1.6). Gravimetric analysis can be used in environmental monitoring to find out how much of a heavy metal ion, such as lead or mercury, is in a sample of water. 

Filtration 1. Fibrous filter 1-50 85-100 Gravimetric or Fibrous filter good for gravimetric analysis... 

However, it is pertinent to mention here that quite a few techniques related to measurement of pharmaceutical substances and reagents involved is more or less common to both gravimetric and volumetric analysis. Besides, in gravimetric analysis, some more additional techniques play a vital role, namely precipitation, filtration, washing of the precipitate and ignition of the precipitate. 

Anal. Calcd. for recrystallized [PtCl2(NH3)2] Cl, 23.6 Pt, 65.0. Found Cl, 23.5 Pt, 65.0. Cl is analyzed potentiometrically after decomposition of a sample with hydrazine in aqueous alkaline medium followed by filtration of metallic Pt and acidification of the filtrate with HN03. The Pt is analyzed gravimetrically after decomposition of a sample by heating with Na2C03. 

In gravimetric analysis, the mass of product from a reaction is measured to determine how much unknown was present. Precipitates from gravimetric analyses are collected by filtration, washed, and then dried. Most precipitates are collected in a fritted-glass funnel (also... 

Modified Waksman s medium was prepared in a Fernbach culture flask. An amount of organic sulfide normalized to an equivalent sulfur content of the standard medium (10 g/1.) was added followed by an emulsifier. The medium was then autoclaved for 30 min at 15 psi (121°C), or, as with the polysulfide and elemental sulfur, sterilization was achieved by membrane filtration. Upon cooling, the medium was inoculated with 10 cc of the pure strain of Thiobacillus thiooxidans. The culture s initial pH value was read, and an initial gravimetric sulfate assay was performed. Thereafter, pH and sulfate values were determined at two-day intervals for 25 days. 

The reducing power of the filtrate towards Fehling s solution is measured either gravimetrically or volumetrically. In the former case the directions given for maltose (see General methods, p. no) are followed and the calculation made in accordance with Table XIV on p. in. 

Finally, the concentrations of all constituents were summated and compared with the gravimetric ally measured mass to establish the unaccounted mass denoted unknown. The assumption here is that the various data sets accurately describe the PM characteristics. The filtration devices employed at the sites were all equivalent to the reference method. However, corresponding studies use different procedures with respect to filter handling, data treatment and selection, analytical techniques, etc. In addition, temporal variation, local site characteristics, artefacts like volatilisation and particle-bound water as well as varying distances from major sources will affect... 

In the determination of sulfate, 2 to 5 g of the analysis sample is mixed with HC1 (2 volumes concentrated HC1 + 3 volumes of water), and the mixture is gently boiled for 30 minutes. After filtering and washing, the undissolved coal may be retained for the determination of pyrite sulfur, or it may be discarded and a fresh sample used for pyrite sulfur. Saturated bromine water is added to the filtrate to oxidize all sulfur forms to sulfate ions and ferrous ions to ferric ions. After boiling to remove excess bromine, the iron is precipitated with excess ammonia and filtered. This precipitate must be retained for the determination of nonpyrite iron if a fresh sample of coal was used for the determination of the pyrite iron. The sulfate is then precipitated with ISaCE, and the BaSC>4 is determined gravimetrically. 

The hairy roots were harvested by paper filtration and rinsed with a large amount of water for root mass measurement. The dry weight, DW, of the hairy roots was gravimetrically measured after drying the harvested roots at 80°C for 24 h. 

Off-line determination of biomass concentration by classical gravimetric methods requires cell separation, washing steps and drying to constant weight. The separation of cells can be made either by centrifugation or by filtration. 

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