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placed over this. The brass collar is then put in place and the jam nut is turned down tightly against the collar. (See detail in Figure 3.) In practice the bottle is charged with about two hundred cc. of reaction mixture and put in place. The washers and wing nuts are screwed down evenly and tightly, and the bottle is evacuated. The wing nuts are then tightened until the vacuum remains constant. The usual procedure of washing the interior with hydrogen and evacuating is carried out. Hydrogen is admitted to the desired pressure. The whole apparatus is then shaken until the reaction is complete, which may be judged from previous calibrations of the system. The bottles will stand a vacuum of 28" and a pressure of about 60 pounds above atmospheric pressure. UP?EP, PIPE e-
&PASS PLATE &'RU~U~~ U' , # s I X E ~ TIM FOIL GASKET
SULPHUR FREE RuddeR DISR ClOSE BRRss COLLAR nE* NU7
MODIFICATION OF THE BUNSEN BURET EUGENE W. BLANK Colgate-Palmolive-PeetCompany. Jersey City, New Jersey
and then tapped from each side to take a standard pipe thread. The quarter-inch pipe is cut to lengths and threaded with standard pipe thread. The length fitted into the top of the upper plate is turned into place leaving about half of the hole clear on the other side. Into this half of the hole is fitted the short length of pipe shown in the detail. The connection between the two "Ts" is a close nipple. The valves are set in place with the inside pressure of the system against the bottom of the valve seat. All pipe connections are soldered, care being taken to protect the Bourden tube of the~gage. The connection on the bottom of the upper plate is made from a 13/4' length of I/," pipe. One end is threaded a distance of I/," to "8" with standard pipe thread. Adjacent to this, the pipe is turned down to take the collar as shown in the detail. This smooth portion should be about a/< long. The rest of the pipe is turned down to take a standard No. 24 thread which is the thread in the valve stem jam nut. The shield for the milk bottle reaction chamber is made from the wire cloth and should fit the bottle snugly. The joined edge of this shield is made tight by cutting away every other wire on each edge so that the extending wires may be interwoven and brazed together. One heavy rubber disk is placed between the bronze rods as a cushion for the bottle and the other one is placed over the short tube a t the bottom of the top plate as another cushion. A large tin-foil gasket is placed over the rubber disk and the sulfur-free disk is
B
UNSEN devised the form of buret closed by means of a section of rubber tubing containing a glass bead.l Such burets are of value in dispensing alkali solutions. Delivery of, the contents of the buret is regulated by seizing the tubing between the thumb and forefinger a t the position of the bead and by means of a gentle pressure a t the top of the bead, forming a channel a t one side of the bead through which the liquid can run out. The use of the bead may be eliminated by sealing off the buret in the manner shown in the diagram. The buret is first sealed shut and then a A-- ---.... small aperture is blown in the side wall near the sealed end. Any unevenness of the buret MODIPICATION OF THE BWNSENBURET wall is smoothed awav with (A) represents secemery paper or by pressing the heated portion of the tion of rubber tubing. ( B ) is a small aperture buret on an asbestos pad. blown in the side mall ~-. ~-~~~The manner of operation is of the buret, and (C) is the sealed portion of essentially the same as that of the buret. the bead-tubing cock.
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TREADWELL-HALL, "Analytical chemistry," Vol. 11, "Quantitative analysis," p. 441, 6th edition, John Wiley & Sons, Inc., New York City, 1924.
