Device for Opening Small Sealed Objects under Vacuum G. P. Schacher, General Engineering Laboratory, General Electric Co., Schenectady,
in mass spectrometry analysis, samples of gas from hermetically sealed containers must be analyzed. often to identify the presence of the components of air. The elimination of atmospheric contamination in such studies presents a major problem. A versatile, easily constructed, sampling fixture has proved very useful in handling such problems. FREQUENTLY
At one end of the device a 12/30 standard-taper joint and stopcock are attached, so that the sampling system can be directly incorporated into the mass spectrometer system. At the other end of the Pyrex KO. 7740 tube a stainless steel flange is attached to the Pyrex No. 7740 through a glass to Fernico seal. A matching steel flange base and neoprene O-ring completes the collecting bottle assembly. The base section has two stainless steel support rods to hold the adapter for the specimen to be examined. T o open a sealed container with this fixture, the object is inserted into a suitable adapter, and the steel point, operating through a stainless steel bellows, is advanced just far enough to hold the object in place. The flanges are then tightened, and the system is
evacuated on the mass spectrometer sample system. After evacuation, the object is punctured by turning the knurled knob to apply pressure through the threaded rod to the steel point.
5 JOINT 4 MY. STOPCOCK
BREAKING POINT
ERNICO TO GLASS 0 RlNQ SEAL
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N. Y. The gas released into the sampling vessel can then be introduced into the mass spectrometer without atmospheric contamination. Condensed moisture and adsorbed gases are often problems, because of the use that has been made of some specimens. The adsorbed surface gases can be removed by winding a resistance heating element about the base section of the tube, and heating during the evacuation stage. In this manner, an encapsulated gas specimen can be examined without contamination by surface adsorbed gases. This fixture has made possible the analysis of gases in such devices as vacuum tubes and small sealed relays. The most recent application has been the determination of the nature of the gas contained in microbubbles in glass. In this case, the glass specimen was held in position by the steel point. The point was positioned so that, on tightening, it punctured the glass, and released the entrapped gas from a bubble directly below it. Using this device with a General Electric analytical mass spectrometer, the gaseous composition of samples of less than 1-cu.-mm. volume a t pressures of less than 0.5 atm. has been determined,
Automatic Potentiometric Titration in Determination of Dissolved Oxygen V. S. Griffiths and M. I. Jackman, Chemistry Department, Battersea College of Technology, London, England
of dissolved D oxygendetermination by a method involving a URING
redox titration, an automatic apparatus was developed. The titration was followed potentiometrically by using an electrode pair, comprising a glass reference electrode ( I , 3-6) and a platinum indicator electrode. A glass electrode was used as a reference, as it introduces no extraneous ions into the solution nor requires replenishing. By a suitable choice of electrode contents ( I ) a shift of end point potential may be obtained, thus making the method more convenient electronically for use in an automatic apparatus.
trapped. One milliliter of manganous sulfate reagent was added and mixed, and 1 ml. of potassium hydroxide solution. The whole was well shaken, allowed to stand for 2 minutes, and then 8
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shaken again prior to the addition of 1 ml. of sulfuric acid. Addition of larger amounts of sulfuric acid did not affect the end point. A suitable aliquot of the mixture was taken, 1 ml. of phos-
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Automatic titration for dissolved oxygen determination
EXPERIMENTAL
Thc reagents were 48% w./v. nianganous sulfate, 70% wv./v.potassium hydroxide, concentrated sulfuric and phosphoric acids, and 0.0125N ferrous ammonium sulfate in 4% n../v. sulfuric acid. Glass-stoppered reagent bottles containing about 120 ml. were filled, care being taken that no air bubble was
D.O. IRON METHOD,P.P.M. VOL. 31, NO. 1, JANUARY 1959
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