Calcium sulfate added

Low-porosity PC No calcium sulfate added Added Na2C03+lignosulfonate... 

The Portland clinker used should contain a high amount of tricaldum silicate, preferably more than 45%. This is necessary as the hydration of this phase produces the calcium hydroxide needed for a pozzolanic reaction of the ash. The hydration of the clinker minerals is mainly responsible for the setting and initial strength development of the cement, as the reaction rate of the fly ash is rather slow. The lydration of the ash contributes to strength only at longer hydration times, but also affects other properties of the hardened material. The calcium sulfate added in the form of gypsum or anhydrite serves to control the setting of the fresh paste in a similar way as in plain Portland cement. 

This PAG contains 1—2% sulfate as soluble calcium sulfate. Sulfate has been found to make PAG products unstable precipitate forms in less than one week at 50°G. Sulfate, however, has also been seen to increase PAG activity in water clarification and is thus intentionally added in one preparation (24). Precipitated calcium sulfate creates a sludge disposal problem. Typical Al content as AI2O2 of PAG products made from alum is 6 —8%. 

Tofu. Tofu is prepared by adding a coagulant such as calcium sulfate to soymilk to precipitate the protein and oil into a gelatinous curd. The curd is then separated from the soluble portion (whey), pressed, and washed to yield a market-ready product. Tofu, a traditional food in Japan (90), was populari2ed in the United States in the late 1970s and is available in many U.S. supermarkets. 

Calcium sulfate (gypsum) may be added to reduce the carbonate to required levels. The reaction is as follows ... 

The polysulfide base material contains 50—80% of the polyfunctional mercaptan, which is a clear, amber, sympy Hquid polymer with a viscosity at 25°C of 35, 000 Pa-s(= cP), an average mol wt of 4000, a pH range of 6—8, and a ntild, characteristic mercaptan odor. Fillers are added to extend, reinforce, harden, and color the base. They may iaclude siUca, calcium sulfate, ziac oxide, ziac sulfide [1314-98-3] alumina, titanium dioxide [13463-67-7] and calcium carbonate. The high shear strength of the Hquid polymer makes the compositions difficult to mix. The addition of limited amounts of diluents improves the mix without reduciag the set-mbber characteristics unduly, eg, dibutyl phthalate [84-74-2], tricresyl phosphate [1330-78-5], and tributyl citrate [77-94-1]. 

Fig. 1. Scanning electron micrograph of dried crystals of 5200 ppm calcium sulfate solution containing (a) zero, (b) 10, and (c) 25 mg/L of added...

Some products are precipitated from the fermentation broth. The insoluble calcium salts of some organic acids precipitate and are col-lec ted, and adding sulfuric acid regenerates the acid while forming gypsum (calcium sulfate) that constitutes a disposal problem. An early process for recovering the antibiotic cycloserine added silver nitrate to the fermentation broth to precipitate an insoluble silver salt. This process was soon obsolete because of poor economics and because the silver salt, when diy, exploded easily. 

A very complete separation of the calcium sulfate may be effected by adding to the concentrated solution 1000 cc. of alcohol, allowing the mixture to stand for 24 hours, and filtering. The alcohol is then distilled from the filtrate and the procedure followed as indicated above. 

Fillers (calcium carbonate, calcium sulfate, aluminum oxide, bentonites, wood flour) increase the solid content of the dispersion. They are added up to 50%, based on PVAc. The purpose of the addition is the reduction of the penetration depth, provision of thixotropic behavior of the adhesive, gap filling properties and the reduction of the costs. Disadvantage can be the increase of the white point and a possible higher tool wear. 

If the water is permanently hard due to MgS04, and lime is added, the precipitates calcium sulfate, CaS04, and magnesium hydroxide, Mg(OH)4, result, which are removed by sedimentation. 

Five hundred grams of mesquite gum (Note i) is dissolved (Note 2) in 3 1. of cold water in a 5-1. round-bottom flask a cold solution of 125 g. of concentrated sulfuric acid in 80 cc. of water is added and the mixture warmed at 8o° for six hours (Note 3) in a large water bath. The acid is neutralized by gradual addition of 140 g. of powdered calcium carbonate (Note 4), and the solution with excess calcium carbonate is heated in a boiling water bath for an hour to complete the neutralization. The calcium sulfate is filtered off and washed with about 2 I. of hot water. The filtrate is concentrated in an evaporating dish (Note 5) on the boiling water bath to a volume of 650-700 cc. 

A 50 ml volume of 0.04 M Ca(N03)2 solution is added to 150 ml of 0.008 M (NH4)2S04 solution. Show that a trial value of the calcium sulfate ion product is 6 X 10-6. Will a precipitate form ... 

A solution of 183 g. (1.10 moles) of triethyl phosphite (Note 1) in 200 ml. of petroleum ether (b.p. 30-60°) is added to a 3-1., three-necked, round-bottomed flask equipped with a mechanical stirrer, a thermometer, a dropping funnel, and an air condenser the open end of the condenser is connected to a drying tube filled with calcium sulfate or calcium chloride. The flask is immersed in a freezing mixture of sodium chloride and ice, and the stirrer is started. When the temperature of the phosphite solution reaches 0°, a solution of 273 g. (1.00 mole) of hexachlorocyclopentadiene (Note 2) in 100 ml. of petroleum ether (b.p. 30-60°) is added through the dropping funnel at such a rate that the temperature remains between 0° and 10°. The addition requires about 4-6 hours. After the addition is complete, the freezing mixture is removed, and the brown, clear solution is allowed to warm up to room temperature. 

A. 2,2-Dichloronorbornane. A 1-1., round-bottomed flask equipped with a mechanical stirrer and a calcium sulfate drying tube is charged with 91.3 g. (0.665 mole) of phosphorous trichloride and 90.0 g. (0.817 mole) of norcamphor (Note 2). The solution is stirred and cooled to 0° in an ice-salt bath, then 193 g. (0.927 mole) of phosphorous pentachloride is added in portions... 

C16-0105. Write the equilibrium reaction and equilibrium constant expression for each of the following processes (a) Trimethylamine, (CH3)3 N, a weak base, is added to water, (b) Hydrofluoric acid, HF, a weak acid, is added to water, (c) Solid calcium sulfate, CaSOq, a sparingly soluble salt, is added to water. 

The elements of the process are as follows. Acid and alkaline wastestreams are collected in a neutralization tank. Here sufficient lime is added to raise the pH to 6.0. At this point, no zinc hydroxide will precipitate but a portion of the iron, calcium sulfate, and other impurities will form a light precipitate. With a coagulant aid, the mixture is sent to a clarifier where a clear overflow containing the dissolved zinc is obtained. 

Plaster of Paris has long been used as a casting material, a cement, and a mortar. If mixed with water, plaster of Paris forms a very soft and pliable mixture. After a very short time, lasting only 5-8 minutes, the wet, pliable mixture sets, that is, it hardens into a stable, firm solid. The setting process entails the incorporation of water molecules (a process known as hydration) into the calcium sulfate hemihydrate and the consequent formation and crystallization of hydrated sulfate of calcium. In other words, when water is added to plaster of Paris, the two combine, again forming gypsum, which soon crystallizes into a hard solid mass ... 

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