Ground Glass Joints Research Articles

Using Ice-Cooled Condensers in Chemistry Laboratory

An ice-cooled condenser, consisting of a jacket built around a tube open to the atmosphere with an outlet for removal of melting ice, is designed for use in academic laboratory classes. The apparatus can be used in place of standard water cooled condensers in setups where refluxing or distillation is performed. With this simple, inexpensive device there is no need for access to running water. Potential flooding due to insecure tubing is no longer a problem. The ice-cooled accessory, produced with standard glass tubing and either 14/10 or 14/20 ground glass joints, is compatible with most commercially available microscale or small scale kits. The device may even be used with an Erlenmeyer flask and a stopper or cork. Two experiments using ordinary household chemicals are suggested, one requiring refluxing and the other distillation.

Ground glass joints—Tape and clip them but don't grease them!

Ground glass joints—Tape and clip them but don't grease them!

Assisted Distillation Cleanup of Pesticide Residues in Animal Fats: New Beadless Distillation Tube

A new assisted distillation tube has been developed which contains no glass beads or glass wool. The sample is injected into the top of the tube, and a septum is not required. Large ground-glass joints (10/19) are used at the gas inlet and at the Florisil trap connection for maximum strength. Existing assisted distillation apparatus was easily modified to accept the new tubes. Recoveries of 9 organochlorine pesticides from butter and cattle fat ranged from 87 to 104% at a tube temperature of 230 degrees C and a nitrogen flow rate of 250 mL/min. No significant change occurred in recoveries of 8 of the 9 pesticides after 85 uses of the beadless tube. Only the recovery of HCB from butter decreased, from 95 to 80%, after 51 runs. The new tube was compared with the Unitrex glass bead-packed concentric tube at flow rates of 230, 400, and 600 mL nitrogen/min. Recoveries from the Unitrex tube were similar to those of the beadless tube for all pesticides except DDT which was significantly lower, indicating incomplete distillation at 250 mL/min and possible partial breakdown at 400 and 600 mL/min. A procedure is introduced for pressurized solvent washing of distillation tubes. This procedure is more efficient than vacuum washing.

Manipulation in an inert atmosphere

A simple and effective means of securing ground-glass joints and stopcocks in reaction vessels under positive pressure of nitrogen and argon that obviates the need for springs.

Formation of chlorinated carbon products during carbochlorination reactions

Production of titanium, zirconium, and potentially aluminum is based on carbochlorination of the respective oxides with subsequent reduction of the product chlorides to metal. Selection of the carbon reagent for the carbochlorination reaction is based on availability, reactivity, purity, and price. Petroleum coke, metallurgical coke, and pyrolyzed petroleum have been used commonly. These reductants, along with carbon monoxide, have been studied at the Bureau of Mines for the carbochlorination of domestic kaolin to produce aluminum chloride. Reactivity has been the major concern, but perusal of pertinent literature indicated that chlorinated carbon byproducts should also be considered. ~ : Exploratory experiments were undertaken to determine if chlorinated carbon compounds may be byproducts of metallurgically important carbochlorination reactions and reactions between chlorine and various forms of carbon. Twelve tests were made in two groups. Group 1 experiments were carried out in a 50-mm-diameter externally heated quartz tube with ancillary, all glass, airand ice-cooled condensers. All of the glassware was washed, rinsed with distilled water, rinsed with pesticide-grade hexane, and heated to 500 ~ before use to remove organic compounds. Teflon tape was used in the ground glass joints that connected the pieces of equipment. The bed materials were mixed and pelletized to facilitate uniform gas flow through the bed. Pellet beds were baked out at 700 ~ under flowing highpurity nitrogen prior to chlorination. During bed bake-out the condensing system was not attached to the reactor. The reaction was carried out by adjusting the reactor temperature and introducing chlorine (commercial grade) along with the nitrogen at 1 1/min each. For Test 1, carbon monoxide was substituted for the nitrogen during the reaction time. After the allotted reaction time, the glassware was cooled under a flow of nitrogen; it was then disassembled, and the chloride product condensers were rinsed with distilled water and with hexane to extract the organic compounds. The water and hexane rinses were combined and partitioned in a 500 ml separatory funnel. The aqueous fraction was extracted three times with 50 ml portions of hexane. The total volume of hexane was dried with anhydrous sodium sulfate and evaporated to 1 ml in high-purity nitrogen at room temperature. Blank tests were made without a bed of material in place. The second group of four tests was made to investigate the effect of carbon types that would not be used as commercial reductants but could indicate the effect of carbon type on the chlorinated products. These tests were carried out in a much smaller quartz and glass apparatus because of the limited quantities of glassy carbon and diamonds* available.

A method for applying a permanent Teflon® coating to ground glass joints

A method for applying a permanent Teflon® coating to ground glass joints

Mass-spectrometric observation of gas evolution in some devices for transmission of rotational motion into a vacuum

Hydrogen evolution and, to a smaller extent, that of hydrocarbon gases is fo0n0 during rotation of vacuum ground-glass joints lubricated by standard vacuum greases. Up to (0.1–50) × 10 12 hydrogen molecules can evolve per one revolution of the inner fitting of the joint. Investigation of the mechanism of the process has demonstrated that molecular hydrogen is formed in reactions of hydrogen atoms generated by a nonidentified primary tribochemical process. Hydrogen evolution was also observed in the process of closing the metal high vacuum valves in the vacuum system of the mass spectrometer: the integral number of hydrogen molecules was about 10 11−10 12.

Modification of the Official Fluorometric Method for Selenium in Plants

Abstract The official first action AOAC fluorometric method for selenium in plants, 3.074–3.078, has been modified to simplify the method and to make it more accurate. The digestion time has been increased from 15 to 30 min past the appearance of perchloric acid fumes to better assure complete oxidation of all forms of selenium to selenite. Preparation of the 2,3-diaminonaphthalene solution, the reagent used for fluorometric analysis, has been changed so that the reagent is stable for several weeks; in the previous writeup, this solution had to be prepared daily. Special equipment (micro-Kjeldahl flasks with ground glass joints) has been eliminated and cyclohexane has been substituted for decahydronaphthalene. The modified method is convenient and applicable to a wide range of materials; it yields results comparable to those from the official method.

A passive seal for ground glass joints

A passive seal for ground glass joints

The Determination of Micro Amounts of Water in Volcanic Rocks Released during Mechanical Grinding

The authors designed a special ball mill made of Pyrex glass for the determination of micro amounts of water released from rock sample during mechanical grinding (Fig.1). A set of balls which is made up of 4 balls of g5 16 mm, 30 balls of 13 mm and 4 10 mm, and 200 balls of 4 5 mm and rocks sample of uniform grain size (1.00 to 0.84 mm) are placed in the ball mill. The ball mill is connected with a cylinder of nitrogen gas, silicagel-P205 drying tubes, gas flow meters and a Karl Fischer titration vessel by a glass and copper pipes, as shown in Fig.2. An adsorbed water in the ball mill is expelled by passing the dried nitrogen gas. After taking off the ground glass joints a, e and f from the ball mill, the ball mill was placed on a revolving holder and rotated at 120 rpm more than two hours. When the ball mill is revolved for 120 minutes, 99.2% of 10 g of a basalt samples are pulverized to pass through a 0.044 mm (325 mesh) testing sieve. It is confirmed that con-tamination of the ball mill with the atmospheric moisture is negligibly small during a five hours run. After pulverizing the sample, the. ball mill is connected with the Karl Fiscer titration vessel in the same way as the prescribed procedure. The water released from rock sample during grinding is transported by flowing the dried nitrogen gas with constant flow rate to the Karl Fischer titration vessel and absorbed into an anhydrous mixture of methyl alcohol and ethylene glycol (1: 1). After that the mixture was titrated by Karl Fischer method. The accuracy is confirmed to be ± 0.02 mg H2O. The amounts of water released from the most usual fresh volcanic rocks and from many glassy rocks was determined to be less than 0.0001%. This value may be considered negligible. The rocks including so-calledresidual magmatic waterand highly hydrated glassy rocks released large amount of water. If the water released on mechanical grinding are disregarded, the amounts of water in the rocks can not be correctly evaluated. Liparites, from Nii-shima and Kozu-shima, absorbed even an extremely small amounts of water which remained in dried nitrogen gas during mechanical grinding and analytical procedure.

A rapid procedure for preparing gas samples for nitrogen-15 determination

A method, which is faster and more convenient than previous techniques, is described for converting ammonium sulphate into nitrogen gas for isotopic analysis on a mass spectrometer. The dry ammonium sulphate sample is contained in a small screw-topped vial, in which it can be stored pending analysis. This vial can be coupled with a neoprene O-ring to a special assembly, evacuated, and the sample oxidised with air-free hypobromite solution from a reservoir in the assembly. By using this procedure the usual inconvenience of de-greasing ground-glass joints on sample tubes is avoided, the difficulty of storing samples prior to analysis is overcome and the de-gassing of solutions prior to the conversion of each sample into nitrogen gas is eliminated. The procedure is particularly suitable when many hundreds of samples are to be analysed.

Elimination of leaks in spherical joints

This short note suggests the use of O-rings to prevent leaks in spherical ground-glass joints without grease.

Beeswax frees frozen ground glass joints

Beeswax frees frozen ground glass joints

An improved microrespirometer for tissue slices

The differential capillary respirometer consists essentially of two chambers, one of which contains a tissue slice, joined by a horizontal capillary. The capillary contains a droplet of fluid which moves if gas is absorbed or evolved in one of the chambers. Compared with open-ended (Warburg) respirometers, this arrangement is free from interference clue to changes in the barometric pressure or environmental temperature. The sensitivity of the differential capillary respirometer depends only on the diameter of the capillary and is not affected by the size of the chambers. The speed of response is inversely related to the chamber volume, however, so the chambers should be as small as possible. The earliest instruments were constructed of glass by Thunberg (1) and developed further by Fenn (2, 3). The Fenn respirometer had the advantages of all-glass construction, i.e., ease of cleaning, visibility of the chamber contents, and rapidity of assembly by ground-glass joints. Disadvantages included the USC of a curved capillary which may interfere with the movement of indicator fluid and the use of side arms for additions during incubation. This latter feature set. a lower limit to the size of the chambers and therefore also to the rapidity of response. In 1940, Cunningham and Kirk (4) described an instrument with the chambers formed from cavities drilled in two metal blocks. This design has been modified in various ways (5-9). Respirometers of metal block construction have the advantage of easier temperature equalization bctween the two chambers and of easier construction of equal chamber size. They may also be made very compact although this requires the use of curved capillaries. These advantages are offset by some serious disadvantages, The instruments are cumbersome to assemble, the chamber

New apparatus for rapid determination of carbon and hydrogen in organic compounds

A new and simple type of apparatus in which a sample is burned explosively is proposed for the rapid determination of carbon and hydrogen in organic compounds. The development of the apparatus has been achieved with a special construction of an inclined combustion tube attached with a sample-boat guide-tube, and connecting the absorption train by means of spherical ground-glass joints and a modified holder. The analytical procedure with this apparatus is extremely simple and rapid. A sample of 2–10 mg is dropped into the combustion tube which has been heated at 800 °–850 °C and burned explosively. Combustion of the sample and the elimination of the resultant gas can be completed in 5 minutes at an oxygen flow-rate of 50 ml per minute. The total time required for an analysis is normally 20 minutes. This apparatus is applicable to the analysis of organic compounds containing halogen, sulfur, and nitrogen, as well as those that explode or sublimate. Accuracy of the analysis with this apparatus is comparable to that of conventional methods.

Hydrolysis of the Phosphorothioate Ion catalysed by Silicone Grease

WHEN preparing trisodium phosphorothioate from thiophosphoryl chloride and sodium hydroxide at 80° according to Akerfeldt1, it was observed that the yields became much smaller when the ground-glass joints of the apparatus used had been treated with silicone grease. In fact, in some cases no trisodium phosphorothioate could be isolated from the reaction mixture. In these instances liberal amounts of silicone grease had been used in lubricating the glass joints.

Improved Gravimetric Vapor-Sorption Apparatus

This improved gravimetric vapor-sorption apparatus was designed for vapor-sorption measurements at 20–50°C with condensable vapors, e.g., water and organic vapors on inorganic and organic adsorbents, such as minerals and resins. The apparatus can be readily adapted to low-temperature adsorption of noncondensable gases, e.g., N2, Kr, and Ar. The system consisted of a helical spring (quartz or tungsten) sorption balance. A Pirani gauge and a mercury manometer permitted the measurement of vapor pressures from several microns to more than 100 mm. Important considerations relevant to the design of helical springs (quartz or metal) were summarized, and a comparative evaluation was made of the advantages and limitations of tungsten and quartz helices. A practical high-vacuum Teflon seal for use in place of greases and waxes on ground glass joints was developed. This seal was designed for use with organic vapors. The aqueous vapor pressures at 20°C were measured for a wide range of concentrations of aqueous sulfuric acid solutions. These data were in excellent agreement (of the order of 1%) with the published data down to pressures of 1 mm of mercury, and they provided a reliable indication of the accuracy of the vapor pressures measured with this apparatus.

Sleeves to replace grease in ground glass joints

Sleeves to replace grease in ground glass joints

Spherical ground glass joints vs. rubber tubing connectors on the C and H absorption train

The effects of ground glass joints and rubber connections in the absorption train were studied by the performance of series of ten combustions each under closely controlled conditions provided by a modified method for rapid combustion, which is described in detail. Statistical tests support the assumption that the rubber connections seem responsible for the occasional occurrence of distinctly erroneous and usually high results in both thePregl and the rapid method for the determination of carbon and hydrogen.

Ground-glass joints leakproof to corrosive chemicals

Ground-glass joints leakproof to corrosive chemicals