Frothing oils

The oxidation products obtained from the heavier fractions deserve attention from the standpoint of lubricant manufacture. The acid portion of the oxidation product has been found to sulfonate very readily. A promising application of the oxidation mixture in its entirety is in the field of ore flotation where it can serve primarily as a frothing oil in flotation mixtures replacing therein the expensive pine oil. Experimental evidence seems to point to the acid content of the oxidized mixture which gives this material its frothing character. 

The flotational separation and enrichment of minerals is one of the most broadly used technological applications that utilizes the control of wetting. Flotation is usually classified as foam (froth), oil, or film flotation, and is based on the difference in wetting of the valuable (flotated) mineral that is to be extracted or concentrated, and the gangue (a barren rock). In froth and... 

Prior to about 1920, flotation procedures were rather crude and rested primarily on the observation that copper and lead-zinc ore pulps (crushed ore mixed with water) could be benefacted (improved in mineral content) by treatment with large amounts of fatty and oily materials. The mineral particles collected in the oily layer and thus could be separated from the gangue and the water. Since then, oil flotation has been largely replaced by froth or foam flotation. Here, only minor amounts of oil or surfactant are used and a froth is formed by agitating or bubbling air through the suspension. The oily froth or foam is concentrated in mineral particles and can be skimmed off as shown schematically in Fig. XIII-4. 

Method 2. Intimately mix 99 g. of pure phthahc anhydride and 20 g. of urea, and place the mixture in a 1 litre long-necked, round-bottomed flask. Heat the flask in an oil bath at 130-135°, When the contents have melted, eflfervescence commences and graduaUy increases in vigour after 10-20 minutes, the mixture suddenly froths up to about three times the original volume (this is accompanied by a rise in temperature to 150-160°) and becomes almost sohd. Remove the flame from beneath the bath and allow to cool. Add about 80 ml. of water to disintegrate the sohd in the flask. Alter at the pump, wash with a httle water, and then dry at 100°. The yield of phthahmide, m.p. 233° (i.e., it is practically pure) is 86 g. If desired, the phthahmide may be recrystalhsed from 1200 ml. of methj lated spirit the first crop consists of 34 g. of m.p. 234°, but further quantities may be recovered from the mother hquor. 

Phenolsulphonephthalein (phenol red). Mix 10 g. of o-sulpho-benzoic anhydride (Section VIII,9), 14 g. of pure phenol and 10 g. of freshly fused zinc chloride in a small conical flask. Place a glass rod in the flask and heat gently over a flame to melt the phenol. Then heat the flask containing the well-stirred mixture in an oil bath at 135-140° for 4 hours. Stir from time to time, but more frequently during the first hour if the mixture froths unduly, remove the flask from the bath, cool and then resume the heating. When the reaction is complete, add 50 ml. of water, allow the water to boil and stir to disintegrate the product. Filter the crude dye with suction and wash it well with hot water. Dissolve the residue in the minimum volume of warm (60°) 20 per cent, sodium hydroxide solution, filter, and just acidify the filtrate with warm dilute hydrochloric acid (1 1). Filter the warm solution, wash with water, and dry upon filter paper. The yield of phenol red (a brilliant red powder) is 11 g. 

The fine mica fraction is deslimed over 0.875—0.147-mm (80—100-mesh) Trommel screens or hydrocylcones, or is separated with hydrosi2ers. The deslimed pulp (<0.589 mm (—28 mesh)) of mica, feldspar, and quart2 is then fed to a froth flotation circuit where these materials are separated from each other either by floating in an acid circuit with rosin amine and sulfuric acid (2.5—4.0 pH), or an alkaline circuit (7.5—9.0 pH) with tall oil amine, goulac, rosin amine acetate, and caustic soda (see Eig. 2). 

The pH of the pulp to the flotation cells is carefliUy controlled by the addition of lime, which optimizes the action of all reagents and is used to depress pyrite. A frother, such as pine oil or a long-chain alcohol, is added to produce the froth, an important part of the flotation process. The ore minerals, coated with an oily collected layer, are hydrophobic and collect on the air bubbles the desired minerals float while the gangue sinks. Typical collectors are xanthates, dithiophosphates, or xanthate derivatives, whereas typical depressants are calcium or sodium cyanide [143-33-9] NaCN, andlime. 

Froth-over When water is present or enters a tank containing hot viscous oil, the sudden conversion of water to steam causes a portion of the tank contents to overflow. 

The foam and froth in the bearing oil, increases the volume and artificially raises the oil level, which leaks through the seals. When enough has leaked to stop foaming, the air bubbles leave the oil resulting in inadequate oil levels. Too much friction heat and failure is the result. 

B-Norcholesterol Acetate (71). A test tube containing 2 g (4.4 mmoles) of (70) is placed in an oil bath at 150° and the temperature of the bath is slowly raised. At 170°, the liquified mass begins to froth and after 15 min the evolution of CO2 is essentially complete. The melt is allowed to stand at 180° for an additional 15 min. After cooling to room temperature and trituration with 5 ml of acetone, long white plates separate. The crystals are removed by filtration and washed with 70% acetone-water to yield 1.74 g (94%) of (71) mp 77-79°. 

In some applications such as catalytic hydrogenation of vegetable oils, slurry reactors, froth flotation, evaporative crystallisation, and so on, the success and efficiency of the process is directly influenced by the extent of mixing between the three phases. Despite its great industrial importance, this topic has received only limited attention. 

Copper, Cu, is unreactive enough for some to be found as the metal, but most is produced from its sulfides, particularly the ore cbalcopyrite, CuFeS2 (Fig. 16.10). The crushed and ground ore is separated from excess rock by froth flotation, a process that depends on the ability of sulfide ores to be wetted by oils but not by water. In this process, the powdered ore is combined with oil, water, and detergents (Fig. 16.1 l). Then air is blown through the mixture the oil-coated sulfide mineral floats to the surface with the froth, and the unwanted copper-poor residue, which is called gangue, sinks to the bottom. 

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