Gypsum calcined

Calcia [1305-78-8] Calci-Bind Calcimar Calcimycin [52665-69-7] Calcination Calcined gypsum Calcined limestone... 

In another process water is introduced into the hot calcined gypsum mass in a kettie to reduce the temperature of a portion of the mass to below the boiling point of water. The mass is then reheated (2). Stabilized setting and water demand properties are claimed as are water demand levels below those attainable through aridizing. 

Plaster is the rehydrated calcined gypsum. The American Dental Association classifies five types of dental plaster according to the physical properties type 1, impression plaster type 11, model plaster type 111, dental stone type IV, high-strength dental stone and type V, high-strength. 

Each 100 g of calcined gypsum theoretically requires only 18.6 mL of water to complete the chemical reaction from the hermhydrate to the dihydrate. Any amount of water greater than 18.6 mL/100 g of powder is excess and reduces the strength of the hardened plaster. When a mixture of the hermhydrate and water hardens, linear expansion takes place. This expansion may amount to as much as 0.5% for plaster. Dental stones also expand on setting, but the amount is significantly less than that permitted in plaster, ie, 0.2% for type III, 0.1% for type IV, and 0.3% for type V. 

Gypsum When gypsum is calcined in rotaiy Idlns, it is first crushed and screened. After calcining it is pulverized. Tube mills are usually used. These impart plasticity and workability. Occasionally such calcined gypsum is passed through ring-roller mills ahead of the tube mills. 

Likewise, the calcination of gypsum drives away water. Calcinating gypsum (composed of hydrated calcium sulfate) causes that part of the water combined with the calcium sulfate to evaporate, leaving a solid, friable residue usually known as plaster of Paris (composed of calcium sulfate hemihydrate) plaster of Paris is used as a cement and mortar as well as an efficient casting material (see Textbox 35). 

Callletet and Mathias law physchem The law that describes the relationship between the mean density of a liquid and its saturated vapor at that temperature as being a linear function of the temperature. kl-o ta an mo thT-os, 16 cajeputol See eucalyptol. ka -3-p3,t6l calabarine See physostigmine. k3 lab-3,ren calcined gypsum See plaster of paris. kal.sTnd jip-som calcined soda See soda ash. kal.sTnd so-do ... 

Calcined gypsum (the half-water salt) can be made into wall plaster by the addition of a filler material such as asbestos, wood pulp, or sand. Without additions, it is plaster of Paris and is used for making casts and for plaster. 

Synonyms annalin calcii sulfas hemihydricus calcined gypsum dried calcium sulfate dried gypsum E516 exsiccated calcium sulfate plaster of Paris sulfate of lime yeso bianco. Appearance a white or almost white, odorless, crystalline, hygroscopic powder. 

The dry weight of the sample is the basis in the calculations involved in the reconstruction of the sample composition. Any error in the dry weight would affect the proper ratios of the different gypsum leases since an error in free water is actually credited to or against water of hydration. Table 2 shows the manner in which an error in percent free water affects the hemihydrate content in a calcined gypsum sample. 

Sodium tetraborate (Spectroflux 200 , Johnson and Matthey Co.) was tried with much greater success. Disks produced by fusion of 0.5000 g of calcined gypsum and 6.00 g of sodium tetraborate (Table 1) produced absolutely clear and transparent disks with perfect surfaces. The use of a higher specimen to flux ratio was dictated by the lower solubility of anhydrite in molten borax. 

As certified gypsum standards were not available commercially, the calibrations were carried out on a set of round-robin analyzed specimens and their mixtures. Three other well analyzed gypsum specimens were supplied by the U.S. Gypsum Co., IL. In addition, several of these had to be spiked with additives in order to expand their calibration ranges on calcium and minor elements. Disks were prepared from calcined gypsums according to the conditions given in Table 1. 

Modem gypsum board production is a complex process that involves the preparation of an aqueous slurry by mixing calcined gypsum (stucco) with water... 

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