Powdered chalk

In 1770 C. W. Scheele showed that the natural product cream of tartar is a salt with a vegetable alkaline base (potash) supersaturated with a vegetable acid (tartaric). When he dissolved cream of tartar [potassium acid tartrate] in boiling water and added powdered chalk to the solution, the lime combined with part of the tartaric acid and gave a copious white precipitate. On evaporating the supernatant liquid he obtained crystals of soluble tartar [normal potassium tartrate] (9, 10). 

K ferrocyanide were also used as ingredients, and a small quantity of powdered chalk was added for stabilization. Some pdrs were graphited(Refs 1,2,3,4 5)... 

Very often particles are blended into polymers, in thermoplasts as well as in thermosets and in synthetic rubbers. This is done for various reasons the aim may be stiffness, strength, hardness, softening temperature, a reduction of shrinkage in processing, reduction of thermal expansion or electric resistance, or, simply, to reduce the price of the material. The fillers used are wood flour, carbon black, glass powder, chalk, quartz powder, mica, molybdene sulphide, various metal oxides, etc. etc. 

Purification of water through sedimentation may be greatly assisted by the introduction of powdered substances and particularly of colloids, although these latter take longer to settle. Frankland,4 in a series of experiments in which some 20 grams of powdered chalk, coke, charcoal,... 

Powdered chalk (mostly calcium carbonate CaC03) reacts rapidly with dilute hydrochloric acid because it has a large total surface area. A stick of chalk has a much smaller surface area, so it reacts much more siowiy. 

The crude oil was carefully mixed with hydrate of potassa and a solution of chloride of iron by strong agitation and then submitted to distillation. The whole of the oil passed over with the water, and perfectly free from prussic acid. By means of a tube, it was separated from the water, and redistilled in a dry apparatus over freshly burned, powdered chalk. 

Neutralizatioa with Lime. This procedure involves treatment of the diluted reaction mixture with Ca(OH)j (milk of lime) or CaCO (finely powdered chalk, limestone, or marble) to convert excess sulfuric acid to insoluble calcium sulfate (which is filtered) and the sulfonic acid to the calcium sulfonate (which appears in the filtrate). Treatment of the filtrate... 

Fig. 13 in Figure 201 depicts an apparatus for generating CO2 hy adding dilute oil of vitriol onto powdered chalk. The water-soluble gas is collected over water having a layer of oil on top. 

FIGURE 2.12 Experimental TJiT ) curve for suspension of water and powdered chalk. 

Reaction of chalk (calcium carbonate) with dilute hydrochloric acid. Left Powdered blackboard chalk reacts faster because the greater surface area increases the amount in contact with the hydrochloric acid. Rightfhe reaction of a piece of blackboard chalk is slower than the reaction of powdered chalk. 

Like above but contains beer and agar. Contains inter alia bile salts and neutral red indicator. Reasonably selective for brewery enterobacteria. Hafnia takes an extra day to grow at 25°C (77°F) on solid medium. Contains inter alia, ethanol and indicator (powdered chalk might be added). Suppresses most brewery microorganisms except acetic acid bacteria. 

By heating powdered chalk in an iron gun-barrel, Priestley obtained a mixture of equal volumes of fixed air and an air which was inflammable, sometimes very weakly, but sometimes pretty highly so this, he found burns blue, and not at all like that which is produced from iron or any other metal, by means of an acid — which puzzled him, as he was fairly sure it came from the iron, though perhaps this inflammable principle may come from some remains of animals in the chalk. This would be carbon monoxide. Priestley, however, thought the blue flame was due to admixture with fixed air. 

Figure 3.18 Particle size distribution by mass of the test powder (chalk)...

Figure 7 Influence of the adsorption (F) of lauric acid from isopropyl alcohol by powdered chalk on moisture uptake (wt. %) of dried powder, filled points and electrical resistance (R) of powder diaphragm in 0.1 n-KCI, open circles (Redrawn from Kolloid. Zh., 1979, 41, 774).

A) A solution containing substances to be separated is poured into the top of a column, which contains powdered chalk. 

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