Gelatin, hydration

The menstruum 1b now to be filtered, in order to remove the sulphite of baryta and other insoluble impurities, Tho filter employed by the patentee is a thin layer of pure gelatinous hydrate of alumina laid on cloth but the liquid may also be forced through unglazed earthen or stono ware. After the solution lias percolated either of these media, it will be found that all ligneous fibre, sillcions and earthy matters, and all particles of insoluble gum have been separated and deposited on the vessels and filter employed, and very little color will remain in the depurated solution but when a very white gum is required, the process of acidulation must be repeated. By evaporating the filtered menstruum, a colorless, tasteless, and pure gum is obtained, the natural properties of which have not been in tho least degree altered. 

Pure alumina is a fine white powder, quite unalterable in the fire. When precipitated from its solution in acids by alkalies,. it forms a very bulky gelatinous hydrate, which,.when dried at 60°, is AljOajfiHO if dried at 100 it becomes AI3 03,3H0. Dry or anhydrous alumina, mixed with water, forms a plastic mass, which admits of being moulded. This property is given to clay by the presence of alumina, and is the foundation of the art of making porcelain or earthenware. 

The oxide which is formed when zinc is burned in the air is the only compound of these elements.. It may also be obtained by heating the carbonate to redness, or by precipitating the sulphate of zinc by a caustic alkali, in which latter case W e obtain a bulky gelatinous hydrate of the oxide. Oxide of zinc... 

Palladium oxide (PdO) can be prepared from Pd and O2. It may be obtained as a yellow gelatinous hydrate (PdO n HjO) that dries to a brown and less hydrated species. Upon further heating it eventually becomes black, but it cannot be completely dehydrated without loss of oxygen. 

Carbon oxide species. Saturated Na2C03 is without action on Ti02- The gelatinous hydrate Ti02-aq, if precipitated from a cold solution of Ti, e.g., by BaCOs, is readily soluble in alkali carbonates, especially (NH4)2C03 . 

On standing, gelatinous aluminium hydroxide, which may initially have even more water occluded than indicated above, is converted into a form insoluble in both acids and alkalis, which is probably a hydrated form of the oxide AI2O3. Both forms, however, have strong adsorptive power and will adsorb dyes, a property long used by the textile trade to dye rayon. The cloth is first impregnated with an aluminium salt (for example sulphate or acetate) when addition of a little alkali, such as sodium carbonate, causes aluminium hydroxide to deposit in the pores of the material. The presence of this aluminium hydroxide in the cloth helps the dye to bite by ad sorbing it—hence the name mordant (Latin mordere = to bite) dye process. 

If a dilute acid is added to this solution, a white gelatinous precipitate of the hydrated tin(IV) oxide is obtained. It was once thought that this was an acid and several formulae were suggested. However, it now seems likely that all these are different forms of the hydrated oxide, the differences arising from differences in particle size and degree of hydration. When some varieties of the hydrated tin(IV) oxide dissolve in hydrochloric acid, this is really a breaking up of the particles to form a colloidal solution—a phenomenon known as peptisation. 

Benzylatnine. Warm an alcoholic suspension of 118-5 g. of finely-powdered benzyl phthalimide with 25 g. of 100 per cent, hydrazine hydrate (CAUTION corrosive liquid) a white, gelatinous precipitate is produced rapidly. Decompose the latter (when its formation appears complete) by heating with excess of hydrochloric acid on a steam bath. Collect the phthalyl hydrazide which separates by suction filtration, and wash it with a little water. Concentrate the filtrate by distillation to remove alcohol, cool, filter from the small amount of precipitated phthalyl hydrazide, render alkaline with excess of sodium hydroxide solution, and extract the liberated benzylamine with ether. Dry the ethereal solution with potassium hydroxide pellets, remove the solvent (compare Fig. //, 13, 4) on a water bath and finally distil the residue. Collect the benzylamine at 185-187° the 3ueld is 50 g. 

The purified gum hydrates slowly in water to give viscous solutions at concentrations up to 1% and clear gelatinous masses at higher concentrations. PsyUium seed gum is a laxative additive and is used in cosmetics and in hair-setting lotions. 

The terms gelatinous alumina or alumina gel covet a range of products in which coUoidal hydrated alumina is the predominant sohd phase. 

Hydrolysis of solutions of Ti(IV) salts leads to precipitation of a hydrated titanium dioxide. The composition and properties of this product depend critically on the precipitation conditions, including the reactant concentration, temperature, pH, and choice of the salt (46—49). At room temperature, a voluminous and gelatinous precipitate forms. This has been referred to as orthotitanic acid [20338-08-3] and has been represented by the nominal formula Ti02 2H20 (Ti(OH). The gelatinous precipitate either redissolves or peptizes to a colloidal suspension ia dilute hydrochloric or nitric acids. If the suspension is boiled, or if precipitation is from hot solutions, a less-hydrated oxide forms. This has been referred to as metatitanic acid [12026-28-7] nominal formula Ti02 H2O (TiO(OH)2). The latter precipitate is more difficult to dissolve ia acid and is only soluble ia concentrated sulfuric acid or hydrofluoric acid. 

Bismuth trioxide may be prepared by the following methods (/) the oxidation of bismuth metal by oxygen at temperatures between 750 and 800°C (2) the thermal decomposition of compounds such as the basic carbonate, the carbonate, or the nitrate (700—800°C) (J) precipitation of hydrated bismuth trioxide upon addition of an alkah metal hydroxide to a solution of a bismuth salt and removal of the water by ignition. The gelatinous precipitate initially formed becomes crystalline on standing it has been represented by the formula Bi(OH)2 and called bismuth hydroxide [10361 -43-0]. However, no definite compound has been isolated. 

The precipitated metallic hydroxides or hydrated oxides are gelatinous in character, and they tend to be contaminated with anions by adsorption and occlusion, and sometimes with basic salts. The values presented in Table 11.2 suggest that many separations should be possible by fractional precipitation of the hydroxides, but such separations are not always practical owing to high local concentrations of base when the solution is treated with alkali. Such unequal concentrations of base result in regions of high local pH and lead to the precipitation of more soluble hydroxides, which may be occluded in the desired precipitate. Slow, or preferably homogeneous, precipitation overcomes this difficulty, and much sharper separations may be achieved. 

A solid emulsion is a suspension of a liquid or solid phase in a solid. For example, opals are solid emulsions formed when partly hydrated silica fills the interstices between close-packed microspheres of silica aggregates. Gelatin desserts are a type of solid emulsion called a gel, which is soft but holds its shape. Photographic emulsions are gels that also contain solid colloidal particles of light-sensitive materials such as silver bromide. Many liquid crystalline arrays can be considered colloids. Cell membranes form a two-dimensional colloidal structure (Fig. 8.44). 

Density of solution and solvent were measurement with Anton Paar densimeter DMA5N. For determining the hydration value is used the following concentrations of gelatin in aqueous solution 0.2, 0.4, 0.5 and 0.6%. 

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