. Bulletin . ^ is allowed to flow into the reser-voir h at any desired rate and thus therate at which it enters the flask is con-trolled. The mercury vapor is condensedin the large U tube c, which is made from25-mm. thin-walled tubing and is 50 , thus giving a condensing tube 1meter long. The tube c is joined to aSprengel suction pump and manometer,and a vacuum of 25 to 30 mm. is main-tained in the apparatus during mercury condenses in the tube c andcollects in the tube d and flows out at thebent-up end. This tube d is about 1 meterlong and 4 mm. in diameter. ELECTBIC H
. Bulletin . ^ is allowed to flow into the reser-voir h at any desired rate and thus therate at which it enters the flask is con-trolled. The mercury vapor is condensedin the large U tube c, which is made from25-mm. thin-walled tubing and is 50 , thus giving a condensing tube 1meter long. The tube c is joined to aSprengel suction pump and manometer,and a vacuum of 25 to 30 mm. is main-tained in the apparatus during mercury condenses in the tube c andcollects in the tube d and flows out at thebent-up end. This tube d is about 1 meterlong and 4 mm. in diameter. ELECTBIC HEATER. IlonRB 20.—Electrically heatedmercury still. Forexplauation,see text The electric heater h is made of as-bestos, Avater glass, and magnesium oxidecement, with heating coils of nichromeribbon on the sides and bottom. Thebottom part of the still is made from strips of asbestos 40 and mm. thick. The nichrome ribbon is placed alongthe edge of these strips, and then they are rolled up together,forming the ribbon into a spiral very close to one side of thewheel thus fabricated. The asbestos strips are well wet withwater and the mixture of water glass and magnesium oxide, andafter they are wound may, while still wet, be dished to fit the bottomof the flask. Thus the flask has a good support and the heating coilis at a place where it will be most effective. A short piece of brasstubing is attached to the end of the nichrome ribbon as a conveni- I ANALYSIS OF MINE ATMOSPHERES 61 ence in starting the roll. This brass tube serves as a hole for thetube q^ and also as one terminal f
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectminesandmineralresou
