Final Report

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Seite 50 - The color to which the clay burns. This may be judged approximately, for clays with several per cent or more of ferric oxide will burn red, provided the iron is evenly and finely distributed in the clay, and there is no excess of lime. The above conditions will be affected by a reducing atmosphere in burning, or the presence of sulphur in the fire gases. 4. The quantity of water. Clays with a large amount of chemically combined water sometimes exhibit a tendency to crack in burning, and may also...
Seite 213 - Food adulterant; paint fillers; paper filling; electric insulators; pumps; fulling cloth; scouring soap; packing for horses' feet; chemical apparatus; condensing worms; ink bottles ; ultramarine manufacture ; emery wheels ; playing marbles ; battery cups; pins, stilts and spurs for potters' use; shuttle eyes and thread guides ; smoking pipes ; umbrella stands ; pedestals ; filter tubes; caster wheels; pump wheels; electrical porcelain; foot rules; plaster; alum.
Seite 107 - ... of any sample that will pass through a sieve of 100 or 150 meshes to the inch, since in the preparation of clays for the market by the washing process they are not required to pass through a screen any finer than the one above mentioned.
Seite 49 - ... and lime (CaO), with the percentage of each given separately. The sum of these two percentages would, however, be equal to the amount of lime carbonate present. While the ultimate analysis, therefore, fails to indicate definitely what compounds .are present in the clay, still there are many facts to be gained from it. The ultimate analysis of a clay might be expressed as follows: Silica (SiO2) Alumina (A12O3) Ferric oxide .... (Fe2O3) Lime (CaO) Fluxing impurities Magnesia ....... (MgO) Alkalies..
Seite 105 - While the temperature of fusion of each cone is given in the preceding table, it must not be understood that these cones are for measuring temperature, but rather for measuring pyrochemical effects. Thus if certain changes are produced in a clay at the...
Seite 93 - The cracking of some fine-grained clays in drying is due partly to the surface shrinking more rapidly than the interior, because the evaporation there is greatest. As the outer portion of the product cannot stretch, it must pull apart and crack. Fire shrinkage. — All clays shrink during some stage of the burning operation, even though they may expand slightly at certain temperatures. The fire shrinkage...
Seite 57 - Coloring act on of iron in unburned clay. — Many clays show a yellow or brown coloration due to the presence of limonite, and a red coloration due to hematite; magnetite is rarely present in sufficient quantity to color the clay; siderite or pyrite may color it gray, and it is probable that the green color of many clays is caused by the presence of silicate of iron, this being specially true of glauconitic ones.
Seite 49 - THE CHEMICAL ANALYSIS OF CLAYS There are two methods of quantitatively analyzing clays. One of these is termed the ultimate analysis, the other is known as the rational analysis. The ultimate analysis. — In this method of analysis, which is the one usually employed, the various ingredients of a clay are considered to exist as oxides, although they may really be present in much more complex forms.
Seite 44 - Mica. — This is one of the few minerals in clay that can be easily detected with the naked eye, for it occurs commonly in the form of thin, .-scaly particles whose bright, shining surface renders them very conspicuous, even when small. Very' few clays are entirely free from mica, even in their washed condition, for, on account of the light scaly character of the mineral, it floats off with the clay particles. Some clays are highly micaceous, but such are rarely of much commercial value.
Seite 57 - Coloring action of iron oxide on burned clay. — All of the iron ores will in burning change to the red or ferric oxide, provided a sufficient supply of oxygen is able to enter the pores of the clay before it is vitrified; if vitrification occurs the iron oxide enters into the formation of silicates of complex composition. The color and depth of shade produced by the iron will, however, depend on...

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