Terra cotta

Barium carbonate prevents formation of scum and efflorescence in brick, tile, masonry cement, terra cotta, and sewer pipe by insolubilizing the soluble sulfates contained in many of the otherwise unsuitable clays. At the same time, it aids other deflocculants by precipitating calcium and magnesium as the carbonates. This reaction is relatively slow and normally requites several days to mature even when very fine powder is used. Consequentiy, often a barium carbonate emulsion in water is prepared with carbonic acid to further increase the solubiUty and speed the reaction. 

Many of the materials used in the most advanced technologies are made from one of the oldest known materials, common clay. Most clays used commercially are oxides of silicon, aluminum, and magnesium. China clay contains primarily kaoli-nite, a form of aluminum aluminosilicate that can be obtained reasonably free of the iron impurities that make many clays look reddish brown, and so it is white. However, other clays contain the iron oxides that cause the orange color of terra cotta tiles and flower pots. 

Abascal-M., R., Harbottle, G., Sayre, E. V., Correlation Between Terra Cotta Figurines and Pottery from the Valley of Mexico and Source Clays by Activation Analysis, In Archaeological Chemistry, Adv. Chem. Ser., 138, 81-99 (1974). 

Transportation Long-distance transport consumes energy and causes pollution. Heavy imported terra-cotta pots like the ones above may seem like a bargain, but the environmental costs are high. 

Pots on display Vintage terra-cotta pots can be as attractive as the plants within them, and many gardeners collect them avidly. Clay pots do, however, dry out guite guickly to save water, display them somewhere that is shaded during the hottest part of the day. 

How often a container plant needs watering depends on the plant type, its size in relation to the container, the type of container (terra-cotta dries out more quickly than plastic), the site (a windy site increases the demand for water), the weather, and the season. Never let containers dry out—plants are much more prone to problems if they are short of water, and dry potting mix is difficult to rewet. In practice, most container plants need daily watering... 

Dinitro-3-hydroxybenzaldehyde gives dark crimson needles of 2,4,6-Trinitro-hydroxy-benzaldehyde- [4-nitro-phenylhydrazone], 02NC6H4NN CC6H(N02)3 0H which explode at 228-30°. Its p-Bromophenylhydrazone, deep olive green crystals with a metallic luster, also explodes violently at 218-20°. The p-nitro-phenylhydrazone derived from 2,6-dinitrohydroxy-benzaldehyde, deep terra cotta crystals, explodes at 240-42°, but the corresponding p-bromophenyl-... 

Type 4 Pottery Hand Grenade had spherical terra cotta body 3 inches in diam with wall 7/16 inch thick. It contd 3.5 oz of Type 88 Explosive and had 4—5 secs delay (Ref 2, p... 

Dinitro (m-anisaldebyde)-(4 -nitropbenyl-kydrazone), terra-cotta ndls rap > 300°. Was prepd by treating 4,6-dinitro-3 methoxybenzaI-dehyde with p-nitrophenylhydrazone as described in Ref 2... 

Drain-tiles, or terra-cotta pipes, are larger than encircled by two bands of letters those of the outer ... 

The terra-cotta vase that was in most general use, both for commercial and domestic purposes, was the amphora. It is either cylindrical in form or egg-shaped, and always has two handles. 

Greek vases in terra-cotta have been occasionally discovered, which were evidently designed for a diversity of uses. There js a vase of s pale clay in the British Museum that is covered with a coating of lime, and when found contained human bones this is evidently a sepulchral vase. Several other vases, also... 

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