The Clays of the State of Washington, Their Geology, Mineralogy, and Technology ...

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State College of Washington, 1910 - 341 Seiten
 

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Seite 48 - F.) of each other. This rapid softening of calcareous clays is one of the main objections to their use, and on this account also it is not usually safe to attempt the manufacture of vitrified products from them, but, as mentioned under Magnesia, the presence of several per cent of the latter substance will counteract this. It has also been found possible to increase the interval between the points of incipient fusion and viscosity by the addition of quartz and...
Seite 95 - A few simple tests will be given to aid in this preliminary prospecting work. 1. A small lump of clay may be roasted in a blue gas flame, as in a gas stove ; if a red or brown color be given to the clay, the percentage of iron is high, probably four per cent, or more. Fire clays are low in iron. 2. By tasting a bit of the clay, bitter salts, alum, epsom.
Seite 89 - Domestic. Porcelain, white earthenware, stoneware, yellow ware and Rockingham ware for table service and for cooking, majolica stoves: polishing brick, bath brick, fire kindlers. "Structural. Brick: common, front, pressed, ornamental, hollow, glazed, adobe; terra cotta; roofing tile- ; glazed and encaustic tile; drain tile; paving brick; chimney flues; chimney pots; doorknobs...
Seite 96 - Very high percentages of lime are apt to ruin the clay. It is not always possible to predict the color of the burned ware from the color of the clay. Red clays will usually burn red, blue clays may burn red or buff. Dark or black clays are usually high in organic matter, and may burn red or buff. The color of clays is discussed more fully in the preceding chapter.
Seite 11 - I. RESIDUAL CLAYS. 1. Kaolin. 2. China or porcelain clay. II. TRANSPORTED CLAYS. A. REFRACTORY (fluxing impurities low). 3. Flint fire clay. 4. Plastic fire clay. B. SEMI-REFRACTORY (fluxing Impurities medium). 5. Paving brick clay and shale. 6. Sewer-pipe clay and shale. 7. Roofing tile clay and shale. 8. Stoneware clay. C. NON-REFRACTORY (fluxing impurities high). 9. Pottery clays, (a) Ball clay, (b) Flower pot clay. 10. Brick and tile clay and shale: (a) Ornamental brick clay and shale. (b) Terra...
Seite 48 - The potter aims to reduce the yellow tint in his white ware by cooling the kiln as quickly as possible to prevent the iron from oxidizing. Fluxing action of iron oxide. — Iron oxide is a fluxing impurity, lowering the fusing point of a clay, and this effect will be more pronounced if the iron is in a ferrous condition or if silica is present.
Seite 75 - ... 92 parts of potash will each produce an equal degree of fusion in the same quantity of the same clay. 3. If a number of fluxes are present in a clay, the fusibility produced will be proportional to the sum of their chemical equivalents. For example, a clay with the formula 0.15 K20) 0.15 CaO \
Seite 55 - Institute, 1875, p. 513. of potash, and the greater number do not contain one per cent. of alkalies. So far as the clays of this state (New Jersey) have been tried, those which are found to have one and a half to two per cent. and upwards of potash have not proved to be good fire-clays. And yet they are otherwise rich and tolerably pure clays. The potash alone appears to explain their low refractory property.
Seite 96 - ... of its shrinkage. If it shrinks out of shape, cracks, or crumbles when dry, its value is very doubtful. For this test, the clay should be ground, thoroughly tempered with water, and dried slowly. 5. If carbonates of lime are present, a few drops of hydrochloric (muriatic) acid may be added, and will be detected by the effervescence or bubbling as the carbonic acid gas passes off.
Seite 68 - Fire shrinkage may begin at a dull red heat, or about the point at which chemically combined water begins to pass off, and reaches its maximum when the clay vitrifies, but does not increase uniformly up to that point.

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