Cement, laboratory

Figure 5.17 Diagrammatic representation of a glass-ionomer cement (Laboratory of the Government Chemist Crown copyright reserved).

Cement, laboratory, 189 Cerium amalgam, 15 Cesium, metallic, 79 Chloroamine, 59 Chlorides, anhydrous, 28, 29 of silicon, 42 Chloroplumbic acid, 48 Chromi-oxalates, 37 Chromous acetate, 122 Chromous chloride, 124, 125 solution, 124 tetrahydrate, 126 trihydrate, 126 Cinnabar, 20 Cobalti-oxalates, 37... 

Cement, laboratory, 1 189 Cerite, extraction of, 2 44 Cerium, phosphor containing strontium sulfide and, 3 23 separation of, from rare earth mixtures, 2 43, 47, 48 test for, 2 50 Cerium amalgam, 1 15 Cerium-group earths, separation of, from yttrium earths by doublesulfate method, 2 44, 46 Cerium (III) magnesium nitrate, 2Ce(N03)s-3Mg(N03)2-24H,0, separation of praseodymium from lanthanum by, 2 57 Cerium(III) nitrate, 2 51 Cerium (IV) nitrate, basic, 2 49 Cesium, cesium azide for preparation of, 1 79... 

Use Phosphorylating agent, dehydrating agent, dental cements, laboratory reagent. 

The concentrations of Fe, Mn, and Mg in calcite cements are often used to interpret their depositional environment. These interpretations use distribution coefficients to estimate the composition of the solution based on an analysis of the calcite cement. Laboratory determinations of these distribution coefficients are typically carried out in batch reactors. Creating a model of the precipitation process in these experiments is helpful for understanding the uncertainties associated with the measurements. If the calcite is precipitated in a batch reactor, Eq. (8.40)... 

Alundum is used for highly refractory bricks (m.p. 2000-2100 C), crucibles, ref ractory cement and muffles also for small laboratory apparatus used at high temperatures (combustion tubes, pyrometer tubes, etc.). 

Deflocculation and Slurry Thinning. Sihcates are used as deflocculants, ie, agents that maintain high sohds slurry viscosities at increased sohds concentrations. Soluble sihcates suppress the formation of ordered stmctures within clay slurries that creates resistance to viscous flow within the various sytems. Laboratory trials are necessary, because the complexity of the systems precludes the use of a universal deflocculant. Sihcates are employed in thinning of limestone or clay slurries used in the wet-process manufacture of cements and bricks, clay refining, and petroleum drilling muds (see also... 

D. Whiting u. D. Stark, Cathodic Protection for Reinforced Concrete Bridge Decks B Field Evaluation, Final Report, Construction Technology Laboratories, Portland Cement Association, Skokie, Illinois, NCHRP 12-13A (1981). 

Organic peroxide-aromatic tertiary amine system is a well-known organic redox system 1]. The typical examples are benzoyl peroxide(BPO)-N,N-dimethylani-line(DMA) and BPO-DMT(N,N-dimethyl-p-toluidine) systems. The binary initiation system has been used in vinyl polymerization in dental acrylic resins and composite resins [2] and in bone cement [3]. Many papers have reported the initiation reaction of these systems for several decades, but the initiation mechanism is still not unified and in controversy [4,5]. Another kind of organic redox system consists of organic hydroperoxide and an aromatic tertiary amine system such as cumene hydroperoxide(CHP)-DMT is used in anaerobic adhesives [6]. Much less attention has been paid to this redox system and its initiation mechanism. A water-soluble peroxide such as persulfate and amine systems have been used in industrial aqueous solution and emulsion polymerization [7-10], yet the initiation mechanism has not been proposed in detail until recently [5]. In order to clarify the structural effect of peroxides and amines including functional monomers containing an amino group, a polymerizable amine, on the redox-initiated polymerization of vinyl monomers and its initiation mechanism, a series of studies have been carried out in our laboratory. 

Karlson et found, from on-site experience of cement-producing plant, that corrosion of Fe surfaces may occur in gases containing O2, SO2 and alkali chlorides such as NaCl and KCl between 300°C and 500°C. They reported that the corrosion rates may be extraordinarily high (5-10 mm/ month) implying liquid-phase corrosion. Laboratory simulation of the plant conditions demonstrated the need for both SO2 and the alkali chloride in the environment. The principle corrosion reaction was found to be ... 

Carbon, analysis, 217, 318, 319 Carbon brushes, examination by x-ray absorptiometry, 97 Cathode follower, 60 Cauchois arrangement, 119, 120, 123 Caustic circle, 119, 120 Cells for liquids, 191, 194 Cements, analysis in Applied Research Laboratories PXQ, 260, 261 Ceramics, analysis by x-ray emission spectrography, 222-224 Cerenkov radiation, 43 Cesium, determination by x-ray emission spectrography, 328 Characteristic-line generator of Eng-strom, 144... 

Concrete, cement block, and wallboard are the most common w all materials found in laboratories. All can be painted after treatment with an approprite sealer or filler. The choice of paint is very important. Both durability and ease of cleaning must be carefully evaluated. Bargain paints are rarely a bargain in the long run, particularly when labor is such a large part of the cost. 

After the capillary has been filled, it is necessary to transport the capillary, usually, to the laboratory. For this purpose it is sealed at bedside. Most commonly it is capped with a plastic cap which is commercially available. However, it can be sealed with either sealing wax or with Kronig s cement, and then be brought to the laboratory. This sealing of the tube is shown in Figure 9. 

Fluoride glasses are difficult to classify because the various constituents can be added to the fusion mixture in several ways. However, glasses of the Laboratory of the Government Chemist (Wilson Kent, 1973 Kent, Lewis Wilson, 1979 Wilson et al., 1980 Hill Wilson, 1988a), which form the basis of many commercial cements, can be represented as... 

Beech, D. R. Bandyopadhyay, S. (1983). A new laboratory method for evaluating the relative solubility and erosion of dental cements. Journal of Oral Rehabilitation, 10, 57-63. 

Ellison, S. Warrens, C. (1987). Solid-state nmr study of aluminosilicate glasses and derived dental cements. Report of the Laboratory of the Government Chemist. 

Mortimer, K. V. Tranter, T. C. (1969). A preliminary laboratory evaluation of polycarboxylate cements. British Dental Journal, 127, 365-9. 

The laboratory impinging jet test for evaluating the acid erosion of dental cements is described in Chapter 10. Using this method with lactic acid-lactate solutions, Wilson et al. (1986b) found, for one cement, that the erosion rate was virtually zero at pH = 5 0, 0-38 % at pH = 4-0 and 5 7 % at pH = 2-7. For a range of cements Wilson et al. (1986a) found erosion rates varying from 3 0 to 5-7 % in lactic add solutions of pH = 2-1. The... 

Consistency, working time, setting time and hardening of an AB cement can be assessed only imperfectly in the laboratory. These properties are important to the clinician but are very difficult to define in terms of laboratory tests. The consistency or workability of a cement paste relates to internal forces of cohesion, represented by the yield stress, rather than to viscosity, since cements behave as plastic bodies and not as Newtonian liquids. The optimum stiffness or consistency required of a cement paste depends upon its application. 

Difficulties have been found in relating laboratory measurements of exotherm behaviour in these AB cements to what happens when they are used in clinical practice. As a consequence there have been few other studies of temperature rise in the setting of such materials. 

The senior author first became interested in acid-base cements in 1964 when he undertook to examine the deficiencies of the dental silicate cement with a view to improving performance. At that time there was much concern by both dental surgeon and patient at the failure of this aesthetic material which was used to restore front teeth. Indeed, at the time, one correspondent commenting on this problem to a newspaper remarked that although mankind had solved the problem of nuclear energy the same could not be said of the restoration of front teeth. At the time it was supposed that the dental silicate cement was, as its name implied, a silicate cement which set by the formation of silica gel. Structural studies at the Laboratory of the Government Chemist (LGC) soon proved that this view was incorrect and that the cement set by formation of an amorphous aluminium phosphate salt. Thus we became aware of and intrigued by a class of materials that set by an acid-base reaction. It appeared that there was endless scope for the formulation of novel materials based on this concept. And so it proved. 

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