Materials, dry

Aminoazobenzene is freely soluble in methylated spirit, although insoluble in water. For recrystallisation, therefore, dissolve the crude substance in boiling methylated spirit, remove from the water-bath, and then add water drop by drop until the solution becomes just cloudy owing to the separation of the solute replace the solution momentarily on the water-bath until the cloudiness disappears, and then at once remove the solution, and allow it to cool slowly. (Alternatively, the crude dry material can be reciystallised from carbon tetrachloride in the usual way.) Aminoazobenzene is thus obtained as yellowish-brown crystals, m.p. 126° yield, 5 g. 

Method 1. From ammonium chloroplatinate. Place 3 0 g. of ammonium chloroplatinate and 30 g. of A.R. sodium nitrate (1) in Pyrex beaker or porcelain casserole and heat gently at first until the rapid evolution of gas slackens, and then more strongly until a temperature of about 300° is reached. This operation occupies about 15 minutes, and there is no spattering. Maintain the fluid mass at 500-530° for 30 minutes, and allow the mixture to cool. Treat the sohd mass with 50 ml. of water. The brown precipitate of platinum oxide (PtOj.HjO) settles to the bottom. Wash it once or twice by decantation, filter througha hardened filter paper on a Gooch crucible, and wash on the filter until practically free from nitrates. Stop the washing process immediately the precipitate tends to become colloidal (2) traces of sodium nitrate do not affect the efficiency of the catalyst. Dry the oxide in a desiccator, and weigh out portions of the dried material as required. 

One side note about the drying attachment is that it need not be a vacuum adapter. Anything, such as a funnel, that can hold a plug of drying material and fit snugly into the condenser will work. 

Conventional laboratory oven used for drying materials. 

Convection. In these mixers an impeller operates within a static shell and particles are moved from one location to another within the bulk. bbon Tjpe. Spiral or other blade styles transfer materials from one end to the other or from both ends to the center for discharge (Fig. 37b). This mixer can be used for dry materials or pastes of heavy consistency. It can be jacketed for heating or cooling. Blades can be smoothly contoured and highly pohshed when cleanliness is an important process requirement. 

Planeta-iy Type. Paddles or whips of various configurations are mounted in an off-center head that moves around the central axis of a bowl or vessel. Material is mixed locally and moved inward from the bowl side, causing intermixing. This mixer handles dry materials or pastes. 

Eor instance, exhaust appHcation is possible with cationic finishes which have an affinity for the anionic groups in polymeric materials. After appHcation, the textile is dried. Durable antistatic finishes require cross-linking of the resin. Cross-linking is usually achieved by subjecting the treated, dried material to heat curing. A catalyst is often incorporated to accelerate insolubilization. 

Chlorates are strong oxidising agents. Dry materials, such as cloth, leather, or paper, contaminated with chlorate may be ignited easily by heat or friction. Extreme care must be taken to ensure that chlorates do not come in contact with heat, organic materials, phosphoms, ammonium compounds, sulfur compounds, oils, greases or waxes, powdered metals, paint, metal salts (especially copper), and solvents. Chlorates should be stored separately from all flammable materials in a cool, dry, fireproof building. 

Most spray-dried instant coffees have been marketed in a granular form, rather than the small spherical spray-dried form, since the mid-1960s. The granular appearance is achieved by steam fusing the spray-dried material in towers similar to the spray drier. Belt agglomerators are also common. 

Values given aie minimuni values. Units for dry material are per 100 grams. 

Dtj basis describes material moisture content as weight of moisture per unit weight of dry material. 

Eailing rate period is a drying period during which the Hquid vaporization rate per unit surface or weight of dry material continuously decreases. 

Wet basis is a material s moisture coateat expressed as a perceatage of the weight of wet material. Although commonly employed, this basis is less satisfactory for dryiag calculatioas than the dry basis for which the percentage change of moisture per unit weight of dry material is constant at aH moisture contents. 

Figure 1 shows the relationship between dry and wet bases. When the wet basis is used to state moisture content, a 2—3% change at moisture contents above 50% may represent a 10—30% change ia evaporative load per unit weight of dry material. 

Fig. 1. Relationship between dry and wet weight bases where dry basis = weight moisture per weight of dry material wet basis = weight moisture per weight of moisture + dry material.

FIG. 12-57 Special conveyor dryer with air jets impinging on surface of bed on first pass. Dried material is crushed and passed again through dryer, with air going through the now-permeable bed. [Chem. Eng., 192 (June 19, 1967).]... 

The physical properties of spray-dried materials are subject to considerable variation, depending on the direction of flow of the inlet gas and its temperature, the degree and uniformity of atomization, the solids content of the feed, the temperature of the feed, and the degree of aeration of the feed. The properties of the product usually of greatest interest are (1) particle size, (2) bulk density, and (3) dustiness. The particle size is a function of atomizer-operating conditions and also of the solids content, liquid viscosity, liquid density, and feed rate. In general, particle size increases with solids content, viscosity, density, and feed rate. 

Ammonium nitrate decomposes into nitrous oxide and water. In the solid phase, decomposition begins at about I50°C (302°F) but becomes extensive only above the melting point (I70°C) (338°F). The reaction is first-order, with activation energy about 40 kcal/g mol (72,000 Btii/lb mol). Traces of moisture and Cr lower the decomposition temperature thoroughly dried material has been kept at 300°C (572°F). All oxides of nitrogen, as well as oxygen and nitrogen, have been detected in decompositions of nitrates. 

Elimination. Porosity in general can be minimized by using clean, dry materials and by properly controlling weld current and arc length. 

The propionamide can be dried over CaO. H2O and unreacted propionic acid were removed as their xylene azeotropes. It was vacuum dried. Material used as an electrolyte solvent (specific conductance less than 10 ohm cm" ) was obtained by fractional distn under reduced pressure, and stored over BaO or molecular sieves because it readily absorbs moisture from the atmosphere on prolonged storage. [Hoover Pure Appl Chem 37 581 I974 Recommended Methods for Purification of Solvents and Tests for Impurities, Coetzee Ed., Pergamon Press, 1982.]... 

Rhodamine B chloride [3,5-his-(diethylamino)-9-(2-carboxyphenyl)xanthylium chloride] [81-88-9] M 479.0, m 210-211"(dec), Cl 45170, A,max 543nm, Free base [509-34-2] Cl 749, pK 5.53. Major impurities are partially dealkylated compounds not removed by crystn. Purified by chromatography, using ethyl acetate/isopropanol/ammonia (conc)(9 7 4, Rp 0.75 on Kieselgel G). Also crystd from cone soln in MeOH by slow addition of dry diethyl ether or from EtOH containing a drop of cone HCl by slow addition of ten volumes of dry diethyl ether. The solid was washed with ether and air dried. The dried material has also been extracted with benzene to remove oil-soluble material prior to recrystn. Store in the dark. 

What would be the ultimate disposal of dry material collected by an ESP at a cement plant kiln outlet What would be the ultimate disposal of wet sludge from a scrubber on a cement plant kiln outlet ... 

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