RAPID HEATING

The recrystallisation of diazoaminobenzene has to be performed with care, as the substance is freely soluble in most liquids and tends moreover to decompose if its solution is not rapidly cooled. Place 2 g. of the crude, freshly prepared, well-drained material in a boiling-tube, add about 15-20 ml. of ethanol and 1-2 drops of 10% aqueous sodium hydroxide solution, and then heat rapidly until boiling if the solution should contain insoluble impurities, filter through a small fluted paper, and at once cool the filtrate in ice-water. The diazoaminobenzene should rapidly crystallise out from the cold and stirred solution filter the crystals rapidly at the pump whilst the solution is still cold, as... 

Force field calculations often truncate the non bonded potential energy of a molecular system at some finite distance. Truncation (nonbonded cutoff) saves computing resources. Also, periodic boxes and boundary conditions require it. However, this approximation is too crude for some calculations. For example, a molecular dynamic simulation with an abruptly truncated potential produces anomalous and nonphysical behavior. One symptom is that the solute (for example, a protein) cools and the solvent (water) heats rapidly. The temperatures of system components then slowly converge until the system appears to be in equilibrium, but it is not. 

Suffice it to say at this stage that the surfaces of most solids subjected to such laser heating will be heated rapidly to very high temperatures and will vaporize as a mix of gas, molten droplets, and small particulate matter. For ICP/MS, it is then only necessary to sweep the ablated aerosol into the plasma flame using a flow of argon gas this is the basis of an ablation cell. It is usual to include a TV monitor and small camera to view the sample and to help direct the laser beam to where it is needed on the surface of the sample. 

In practice, direct insertion of samples requires a somewhat more elaborate arrangement than might be supposed. The sample must be placed on an electrode before insertion into the plasma flame. However, this sample support material is not an electrode in the usual meaning of the term since no electrical current flows through it. Heating of the electrode is done by the plasma flame. The electrode or probe should have small thermal mass so it heats rapidly, and it must be stable at the high temperatures reached in the plasma flame. For these reasons, the sort of materials used... 

When the dihydrate is carefully heated to 100°C it loses its water to give anhydrous oxaUc acid. On the other hand, when the dihydrate is heated rapidly or ia a sealed tube, it melts at 101.5°C. 

Metalloid peroxides behave as covalent organic compounds and most ate insensitive to friction and impact but can decompose violentiy if heated rapidly. Most soHd metalloid peroxides have weU-defined melting points and the mote stable Hquid members can be distilled (Table 3). Some... 

C2S2, is a red Hquid (mp —0.5° C, bp 60—70°C at 1.6 kPa (12 mm Hg)) produced by the action of an electric arc on carbon disulfide (1 4). The stmcture has been shown to be S=C=C=C=S on the basis of its reactions to form malonic acid derivatives and on the basis of physical measurements. It is unstable and decomposes ia a few weeks at room temperature it decomposes explosively when heated rapidly at 100—120°C with formation of a black polymeric substance (C2S2) (5,6). Dilute solutions ia CS2 are fairly stable, but photochemical polymerisation to (C2S2) occurs. 

Pentahydrate is reversibly converted to an amorphous dihydrate, at 88°C and 0.26 kPa (2 mm Hg) or by boiling with xylene (73,75). The heat of dehydration for the pentahydrate to tetrahydrate has been calculated to be 53.697 kj (12.834 kcal) per mole of water (74). Thermogravimetric analyses show that 2.75 moles of water are lost on heating to 140°C. Like borax, pentahydrate puffs when heated rapidly to give a product having a bulk density of 0.042 g/mL (79). 

High-Intensity Mixer. Mixers such as that shown in Fig. 18-44 combine a high shear zone with a fluidized vortex mixing action. Blades at the bottom of the vessel scoop the batch upward at peripheral speeds of about 40 m/s (130 ft/s). The high shear stress (to 20,000 s" ) and blade impact easily reduce agglomerates and aid intimate dispersion. Since the energy input is high [200 kW/m (about 8 hp/fE)h even powdery material is heated rapidly. 

A simplified model of PC combustion includes the following sequence of events (I) on entering the furnace, a PC particle is heated rapidly, driving off the volatile components and leaving a char particle (2) the volatile components burn independently of the coal particle and (3) on completion of volatiles combustion, the remaining char particle burns. Whue this simple sequence may be generally correct, PC combustion is an extremely complex process involving many interrelated physical and chemical processes. 

As the windings are heated rapidly, the test voltage must be applied as quickly as possible. Care should be taken to ensure that the motor temperature does not... 

Since the pinacol decomposes near its melting point the latter will vary with the rate of heating. The temperatures reported here were obtained by slow heating if the tube is placed in a bath at 150° and heated rapidly, the observed melting or decomposition point is 193-195 . 

Isoquinuclidone A 5-g portion of cis- and rra/ij-4-aminocyclohexanecarboxylic acid is mixed with 30 ml of Dowtherm At and heated rapidly to reflux in a flask fitted with a short distilling column. Water distils during the heating, which is continued for about 20 minutes. At this time, the mixture is homogeneous. The cooled solution is... 

Then, as described in U.S. Patent 2,55416, the 2-acetylamido-5-mercapto-1,3,4-thiadiazole is converted to the sulfonyl chloride by passing chlorine gas into a cooled (5°-10°C) solution in 33% acetic acid (66 parts to 4 parts of mercapto compound) used as a reaction medium. Chlorine treatment is continued for two hours. The crude product can be dried and purified by recrystallization from ethylene chloride. The pure compound is a white crystalline solid, MP l94°C,with decomposition, when heated rapidly. The crude damp sulfonyl chloride is converted to the sulfonamide by addition to a large excess of liquid ammonia. The product is purified by recrystallization from water. The pure compound is a white, crystalline solid, MP 259°C, with decomposition. The yield of sulfonamide was 85% of theory based on mercapto compound. 

Step B 3-Carbethoxy-4-Hydroxy-8-Trifluoromethylquinoline - A mixture of 113 grams of crude ortho-trifluoromethylanilinomethylene ethyl malonate from Step A, and 115 cc of phenyl oxide was heated rapidly under an inert atmosphere. At about 195°C, the ethanol formed began to distill off. At the end of about 30 minutes, the interior temperature reached 250°C and the reaction mixture was heated to reflux. Reflux was maintained for 1 hour and the mixture was then cooled, 25 cc of acetone were added and the mixture was allowed to crystallize. The mixture was filtered and the crystals thus formed were washed and dried to obtain 71.5 grams of 3-carbethoxy-4-hydroxy-8-trifluoromethylquino-line with a melting point of 210° to 214°C, which was used as is for the following stage. 

A mixture of 24.1 g (0.10 mol) of 3-o-methoxyphenoxy-2-hydroxy-1 -propyl carbamate and 6.0 g (0.10 mol) of urea was heated rapidly to the temperature range of 180°C to 200°C, and maintained there for five hours. The reaction melt was poured into 50% ethyl alcohol, from which the product crystallized as a white solid. The crude yield was 18.3 g (82%) melting point 131.5°C to 137 t. Crystallization from water and 95% alcohol gave 9.0 g (40.3%) of pure 5-o-methoxyphenoxymethyl-2-oxazolidone melting point 141°Cto 143. This melting point was not depressed when the material was mixed with an authentic sample. In additional runs acetone was used Instead of ethyl alcohol with equivalent results. 

Urea (118 g, 1.96 mols) was added to 192 g (0.98 mol) of 3-(3, 5 -dlmethylphenoxy)-1,2-propane-diol which had previously been heated to 150°C. The reaction mixture was then heated rapidly to 195° to 200°C and maintained at this temperature for 5 hours with constant stirring. The resulting mixture was partitioned between water and ethyl acetate and the ethyl acetate layer was dried over sodium sulfate and concentrated. The residue was distilled in vacuo and the fraction boiling at 220° to 225°C/1.5 mm was collected. Yield, 172 g (79%). The distillate was crystallized from dry ethyl acetate MP, 121.5° to 123°C. 

Cost breakdown of a high production mold or die is approximately as follows Material cost used to about 12 to 20%, design about 5 to 10%, mold building hours about 40 to 60%, and profit at about 5 to 10%. In general they are very expensive with the major cost principally in machine building labor. The proper choice of materials of construction for their different parts is paramount to quality, performance, and longevity of a mold/die. Add good machinability of component metal parts, material which will accept the desired finish (polished, textured, etc.), ability to transfer heat rapidly and evenly, capability of sustained production without constant maintenance, etc. 

Melamine Picrate. C3H6N6.C6H307N3 mw 355.27, N 35.49%, OB to C02 -69.8% light yellow powd mp 316-17° nearly insol in w. May deflagrate when heated rapidly (Refs 1, 2, 3 4)... 

Na3N decomps appreciably at 150°, at 200° in about one hour, and at 350° in a few minutes. When heated rapidly nitrogen is evolved with expl violence (Refs 1, 2, 5 6)... 

It is decompd by moisture or on slow heating to about 50°. When heated rapidly to ca 50°, it detonates. It is extremely sensitive to friction, and sometimes detonates on removing the cork from its container. It also detonates on contact with coned sulfuric acid, coned KOH or ammonia Ref L. Gody, Traite des Materieres Explosifs , Namur (1907), 531... 

It forms color crysts which lose dioxane on slow heating, but explds violently when heated rapidly to higher temps (Ref 14a)... 

SI sol in cold w freely sol in hot w, ale, benz, eth, CS2 and alkali hydroxides. Highly toxic by ingestion and inhalation. Forms salts, of which the Pb salt explds mildly when heated rapidly (Ref 1, [209])... 

Copper salt. Cu(C7H5N4)2. Crysts, mp decomps at 130° and deflagrates when heated rapidly on a Pt foil... 

Phloroglucinol (1,3,5-Trihydroxy benzene, 1,3,5-Trioxy-benzol in Ger). C6H3(OH)3,mw 126.11, white to yellowish crysts mp 200—209° when heated slowly 212—217° when heated rapidly bp, sublimes with decompn. SI sol in w, sol in ale and eth. Combustible. Can be prepd by fusion of resorcinol with caustic soda, or by reduction of trinitrobenzene. It is highly toxic. by ingestion, inhalation and skin absorption, and is a strong irritant to skin and mucous membranes Refs 1) Beil 6,1092, (545) [1075]... 

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