Volume precipitate

Two more recent appHcations for amorphous siHcas are expected to grow to large volumes. Precipitated siHcas are used ia the manufacture of separator sheets placed between cells ia automotive batteries. Their function is to provide a controlled path for the migration of conductive ions as a result of the porosity of the siHca particles. Additionally, both precipitated siHcas and aerogels are being developed for use ia low temperature iasulation, where the low thermal conductivity of the dry siHca powders makes them useful ia consumer products such as refrigerators (83). 

The product is hydrogenated in 4,000 cc of ethanol at room temperature and under normal atmospheric pressure with a catalyst prepared In the usual manner from 400 g of Raney nickel alloy. The calculated amount of hydrogen is taken up in approximately 75 hours. After filtration and evaporation to a small volume, the residue Is distributed between 1,000 cc of chloroform and water each. The chloroform solution is then dried over sodium sulfate and evaporated to a small volume. Precipitation of the hydrogenation product with petroleum ether yields an amorphous white powder which Is filtered by suction, washed with petroleum ether and dried at 50°C In a high vacuum. 1. athyl-2-podophyllinic acid hydrazide is obtained in a practically quantitative yield. 

Plasma Protein Precipitated (%) Volume Precipitant Added/Volume Plasma... 

TABLE 6.1 Full Transient Solution Adjustment Factor, g, in Equation (6.42) as a Function of Volume Precipitate for the Exact Solution to Equation (6.35) as Solved by Nielsen ... 

Due to their high specific surface area and pore volume, precipitated iron catalysts are characterized by high specific activity and can thus be operated at low temperatures. They can be u.sed in fixed bed and slurry phase reactors. 

Precipitation was achieved by adding 3.5 dm of Al2(S04)3 solution to NaOH solution of the same volume. Precipitated aluminium hydroxide was rinsed with water, and had the excess of ions removed using an ion-exchange process. A measure of aluminium hydroxide activity was the maximal exchange capacity towards 8303 ions at pH = 7. 

There is no discernible pattern to the spatial distribution of siderite other than its sporadic occurrence within wells and within the field. Ankerite is also sporadically distributed and restricted to samples located at or close to the boundary with the underlying shales of the Drake Formation (Dunlin Group Fig. 4). Systematic distribution of diagenetic ankerite in the vicinity of mudstone units has been noted by Macaulay et al. (1993) in Jurassic sandstones of the Magnus field. North Sea. Siderite and ankerite represent minor cements in terms of total volume precipitated at field scale. 

To hasten the rate of filtering of either a gelatinous or large volume precipitate, a vacuum can be applied. The vacuum is low level, and a water aspirator is sufficient. For large volumes of precipitate, a Buchner funnel is used. Figure 37-14 shows the most common arrangement with a safety trap attached. Circles of filter paper are placed in the bottom of the funnel to cover the holes. A small layer of charcoal is sometimes added on top of the paper, if the solution is to be clarified. 

For smaller volume precipitates, such as those collected in a crucible when the precipitate is to be weighed, then porcelain or glass crucibles with sintered glass bottoms of various porosities are used. Some are shown in Figure 37-17. Porosities are ultrafine (UF) 0.9 to... 

For volume precipitation to occur, it is necessary to have precursor-solute which should have the following properties [3,28,51] ... 

Obviously, the precursor for Ti02 had an exceptionally low concentration and preferred surface precipitation, while concentration of precursors for all other observed systems was much higher than in the case of Ti02 and they preferred volume precipitation. 

The powder systems S, A, and B, in the shape of full spheres are obtained, and the dominant mechanism of precipitation of these powders was volume precipitation. It is conditioned by relatively high concentration of given systems (expressed in percentage) with Si02 — 30%, with PWg026 — 20%, and with calciumhydroxysiapatite — 6.5%. 

With the colloid system that creates Si02 nanosols, mechanism of volume precipitation is present, almost completely due to its high concentration and the tendency of dense colloid systems to 3D linking inside complete volume of the sample. 

F) and (G) was obtmned by pouring a concentrated aqueous solution of (D) into an amount of absolute alcohol which would result in a final alcohol concentration of approximately 95 per cent by volume. Precipitate (G) which had been freed from such lipids as are soluble in ether, acetone, and strong cold alcohol, and from all but a trace of protein, sulfur, and iron, proved effective when fed daily in amounts of 9-14 g. This is equivalent to approximately 200-400 g. of whole liver. (It was later found that fraction... 

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