. Dental metallurgy, for the use of dental students and practitioners. th lime;calcium sulphide and sulphate are formed and the mercuryset free. Reaction: 4HgS + 4CaO = 4Hg + 3CaS + CaS04 3. Cinnabar is heated with iron and the following reactiontakes place: 2HgS + Fc + 02 = 2Hg + FeS 4- SO>. PROPERTIES 123 In the first process the sulphide is heated in kilns wherethe reduction takes place. The temperature of the kilns issufficiently high to volatilize the reduced mercury, the vaporof which passes into brick condensing chambers (Fig. 43, C).For dental purposes the mercury is again distilled
. Dental metallurgy, for the use of dental students and practitioners. th lime;calcium sulphide and sulphate are formed and the mercuryset free. Reaction: 4HgS + 4CaO = 4Hg + 3CaS + CaS04 3. Cinnabar is heated with iron and the following reactiontakes place: 2HgS + Fc + 02 = 2Hg + FeS 4- SO>. PROPERTIES 123 In the first process the sulphide is heated in kilns wherethe reduction takes place. The temperature of the kilns issufficiently high to volatilize the reduced mercury, the vaporof which passes into brick condensing chambers (Fig. 43, C).For dental purposes the mercury is again distilled to removethe least trace of base metal with which it may be contami-nated. This product is known as redistilled mercury. Commercial mercury may also be purified by the electro-lytic process. By this method it may be freed from admix-tures of zinc, cadmium, bismuth, lead and tin. A crudetest which is often used to discover if mercury contains basemetal impurities is to allow some of the mercury to flow overa piece of white cardboard. If the mercury leaves a track or. Fig. 43 tail, base metals are present; however, mercury which willnot show this reaction may still contain impurities in sufficientamounts to render it useless for dental purposes. Properties.—Solid mercury exists only at a temperaturebelow —° C, and at ordinary temperatures it is a liquid,being an exception to the general statement that metalsare solids at ordinary temperatures. The solid metal is veryductile and is so soft that it may be cut with a knife. Itranks low in heat and electrical conducting powers, and alsohas a low coefficient of expansion on heating. During solidi-fication it contracts considerably, its specific gravity risingfrom to and forms octahedral crystals. Mercury inextremely thin films appears a violet color by transmitted light. Under a pressure of 760 mm. mercury boils at °, 124 MERCURY giving a colorless vapor. Mercury does not tarnish uponexposure to the air a
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Keywords: ., bookcentury1900, bookdecade1910, bookpublisherphila, bookyear1917
