Powders looseness

Peyote is ingested fresh (as whole dried buttons) or as powder (loose in capsules or pressed into tablets). Mescaline sold on the street (see Table 6—2) is generally not what it is claimed to be but is most likely one of the following DOM, PCP, LSD, caffeine, or amphetamine-related stimulants (Kulberg... 

The angle of repose may also be measured using a plane sheet to which is stuck a layer of particles from the powder. Loose powder is then poured on to the sheet which is then tilted until the powder slides. The angle of slide is known as the static angle of repose or the drained angle. 

Nitrocellulose powder Rifle flake non-polished powder loosely poured 0.79 3800... 

Properties White, slightly hygroscopic, crystalline powder. Loose bulk d about 37 lb/ft3, granulated 57 lb/ft3. Active ingredient about 60% available chlorine decomposes at 230C. 

In order to increase the ultrasound effects, the reduction of all the samples was performed with hydrazine at 80°C for 20 min undertaking the solid-liquid suspension at a sonication of frequency 21 kHz and power 30 W, calculated with the calorimetric method [7]. This particular power was chosen in order to minimize the possible effects of destruction of the support in fact the transformation of the alumina in fine powder, loosing the morphological structure was observed increasing the power just at 45 W. A change in the alumina phase (usually from n to a phase) was also detected in similar condition at room temprature [8],... 

Rotation molding powder. Loosely compacted fluff. 

Air separation in the pseudoliquefied layer as shown in Fig. 16.9(a) allows separation of particles with respect to their geometric form and their weight. The particles move in the turbulent gas flow for several hours so that the powder looseness is increased and the specific surface of the particles is reduced. The separation efficiency by air separation is greater than by sieving, as is indicated in Fig. 16.9(b). 

Fig. 16.10 Powder looseness as a function of humidity (1) powder annealed in electric furnace, (2) powder annealed in gas furnace.

Metals ferrous and non-ferrous Rod or bar structures Granules or powder loose, sintered Fibres loose, sintered Sheets perforated (punched, etched) Wire wound cartridge, woven mesh, sintered mesh Expanded mesh ( Expamet ) Foam... 

Carbon natural Granules or powder loose, bonded, embedded... 

Lead formate separates from aqueous solution without water of crystallisation. It can therefore be used for the preparation of anhydrous formic acid. For this purpose, the powdered lead formate is placed in the inner tube of an ordinary jacketed cond ser, and there held loosely in position by plugs of glass-wool. The condenser is then clamped in an oblique position and the lower end fitted into a receiver closed with a calcium chloride tube. A current of dry hydrogen sulphide is passed down the inner tube of the condenser, whilst steam is passed through the jacket. The formic acid which is liberated... 

Make a thin paste of 21 5 g. of finely-powdered o-tolidine (a commercial product) with 300 ml. of water in a 1-litre beaker, add 25 g. (21 ml.) of concentrated hydrochloric acid, and warm until dissolved. Cool the solution to 10° with ice, stir mechanically, and add a further 25 g. (21 ml.) of concentrated hydrochloric acid (1) partial separation of o tolidine dihydrochloride will occur. Add a solution of 15 g, of sodium nitrite in 30 ml. of water as rapidly as possible, but keep the temperature below 15° a slight excess of nitrous acid is not harmful in this preparation. Add the clear, orange tetrazonium solution to 175 ml. of 30 per cent, hypophosphorous acid (2), and allow the mixture to stand, loosely stoppered, at room temperature for 16-18 hours. Transfer to a separatory funnel, and remove the upper red oily layer. Extract the aqueous layer with 50 ml, of benzene. Dry the combined upper layer and benzene extract with anhydrous magnesium sulphate, and remove the benzene by distillation (compare Fig. II, 13, 4) from a Widmer or similar flask (Figs. II, 24, 3-5) heat in an oil bath to 150° to ensure the removal of the last traces of benzene. Distil the residue at ca. 3 mm. pressure and a temperature of 155°. Collect the 3 3 -dimethyldiphenyl as a pale yellow liquid at 114-115°/3 mm. raise the bath temperature to about 170° when the temperature of the thermometer in the flask commences to fall. The yield is 14 g. 

Examples are provided by the work of Carman and Raal with CF2CI2 on silica powder, of Zwietering" with nitrogen on silica spherules and of Kiselev" with hexane on carbon black and more recently of Gregg and Langford with nitrogen on alumina spherules compacted at a series of pressures. In all cases, a well defined Type II isotherm obtained with the loose powder became an equally well defined Type IV isotherm with the compact moreover both branches of the hysteresis loop were situated (drove the isotherm for the uncompacted powder, but the pre-hysteresis region was scarcely affected (cf. Fig. 3.4). The results of all these and similar... 

There are three basic forms of abrasives grit (loose, granular, or powdered particles) bonded materials (particles are bonded iato wheels, segments, or stick shapes) and coated materials (particles are bonded to paper, plastic, cloth, or metal). 

Abrasive appHcations for industrial diamonds include thek use in rock drilling, as tools for dressing and tmeing abrasive wheels, in polishing and cutting operations (as a loose powder), and as abrasive grits in bonded wheels and coated abrasive products. 

Typically, dry potassium nitrate is pulverized in a ball mill. Sulfur is milled into cellular charcoal to form a uniform mix in a separate ball mill. The nitrate and the sulfur—charcoal mix are screened and then loosely mixed by hand or in a tumbling machine. Magnetic separators may be used to ensure the absence of ferrous metals. The preliminary mix is transferred to an edge-mimer wheel mill with large, heavy cast iron wheels. A clearance between the pan and the wheels is required for safety purposes. The size of this gap also contributes to the density of the black powder granules obtained. Water is added to minimize dusting and improve incorporation of the nitrate into the charcoal. The milling operation requires ca 3 to 6 h. 

For plastic-bonded materials, no clear-cut expression for the coercivity is known. It may be expected that it is rather similar, but with a smaller influence of B. For loosely packed powders, the B influence has become zero and should be multiphed by 0.48 to account for the isotropy (71). In all cases high coercivity is obtained by using small grains with limited plate-like shape, ie, the value of Nis not too high. 

Apparent Density. This term refers to the weight of a unit volume of loose powder, usually expressed in g/cm (l )- The apparent density of a powder depends on the friction conditions between the powder particles, which are a function of the relative surface area of the particles and the surface conditions. It depends, furthermore, on the packing arrangement of the particles, which depends on the particle size, but mainly on particle size distribution and the shape of the particles. 

The characteristics of a powder that determine its apparent density are rather complex, but some general statements with respect to powder variables and their effect on the density of the loose powder can be made. (/) The smaller the particles, the greater the specific surface area of the powder. This increases the friction between the particles and lowers the apparent density but enhances the rate of sintering. (2) Powders having very irregular-shaped particles are usually characterized by a lower apparent density than more regular or spherical ones. This is shown in Table 4 for three different types of copper powders having identical particle size distribution but different particle shape. These data illustrate the decisive influence of particle shape on apparent density. (J) In any mixture of coarse and fine powder particles, an optimum mixture results in maximum apparent density. This optimum mixture is reached when the fine particles fill the voids between the coarse particles. 

Tap Density. Tapping a mass of loose powder, or more specifically, the appHcation of vibration to the powder mass, separates the powder particles intermittently, and thus overcomes friction. This short-time lowering of friction results in an improved powder packing between particles and in a higher apparent density of the powder mass. Tap density is always higher than apparent density. The amount of increase from apparent to tap density depends mainly on particle size and shape (see Table 4). 

The manufacture of metal in powder form is a complex and highly engineered operation. It is dominated by the variables of the powder, namely those that are closely connected with an individual powder particle, those that refer to the mass of particles which form the powder, and those that refer to the voids in the particles themselves. In a mass of loosely piled powder, >60% of the volume consists of voids. The primary methods for the manufacture of metal powders are atomization, the reduction of metal oxides, and electrolytic deposition (15,16). Typical metal powder particle shapes are shown in Figure 5. 

Compression ratio is the dimensional relationship between the loose and compacted powder at a given compacting pressure. 

Porous parts and bearings are made by both the press and sinter techniques, whereas filters are made by loose powder sintering. The metals most commonly used for P/M porous products are bron2e, stainless steel (type 316), nickel-base alloys (Monel, Inconel, nickel), titanium, and aluminum. 

Niobium pentoxide also is reduced to metal commercially by the aluminothermic process. The finely ground powder is mixed with atomized aluminum and an accelerator compound which gives extra heat during reaction, then is ignited. The reaction is completed quickly and, after cooling, the slag is broken loose to free the metal derby which is purified by electron-beam melting. 

Potassium Methylate. Potassium methoxide [865-33-8] KOCH, mol wt 70.13, is a fine, free-flowing, yellowish-white, caustic, hygroscopic powder purity 96.5—99% powder density after loose shaking, 0.75 g/mL apparent density (packing weight), 1.00 g/mL medium grain size, 0.05 —0.8 mm easily soluble in alcohols (33% in methanol at 20°C), insoluble in hydrocarbons. 

---