Types of ground glass joints


The type of carbon dioxide absorption tube S (Fig. 85) which U recommended is shown in detail in Fig. 86. In this tube the composite filling of soda-lime and a small packing of magnesium perchlorate are kept in separate chambers which are a-put in contact only while gas is flowing, by rotating a ground-glass joint tap Tj which divides the tube into two compartments the perchlorate being packed in what is virtually an enlarged hollow tap-stopper a (Fig. 86) at one end of the tube. By keeping these two elements of tube-packing out of contact with each other except when the tube is being used to absorb carbon dioxide, the "life of the tube, before repacking becomes necessary, is much increased. In filling the carbon dioxide absorption tube S of this type (Fig 86), the hollow stopper a, having a small hole at the lower end, is charged in turn with a glass-wool plug b, perchlorate c, and a second glass-wool plug d, and the glass stopper e is then fixed into a with warm glass cement. The absorption stopper a is carefully greased at the neck T, and at the lower end opposite S, and then fitted into the main absorption tube S like an ordinary tap the unit now constitutes the tap T,. The main soda-lime chamber f is then filled from the other end of S with a glass-wool plug g, soda-time h, and a second glass-wool plug j, and the greased tap T finally inserted. The presence of perchlorate is necessary as the FiG. 86. oda-lime contains a little moisture which is driven off by the continued passage of oxygen, and this would cause low results for carbon if the water were not prevented from leaving the tube by the "safety" layer of perchlorate.  [c.471]

Apparatus. The essential part of the apparatus consists of a long narrow tube (20-30 cm. long and 1-3 cm. diameter) this holds 50-100 g. of adsorbent and may retain several grams of the adsorbate, although the amount is usually somewhat smaller. Fig. II, 46, 2 illustrates a simple form of apparatus the adsorbent is supported on a plug of cotton or glass wool for wide tubes a perforated disc, covered by a pad of cotton or glass wool, may be used. Fig. II, 46, 3 depicts a column fitted with a ground glass joint and a perforated glass plate or fritted glass disc is sealed into the lower part of the ground joint f the removal of the column  [c.158]

Mix intimately in a glass mortar 35 g. of saccharin (Section IV,209) and 70 g. of phosphorus pentachloride, transfer to a 250 ml. round-bottomed flask connected by a ground glass joint to a reflux condenser attach the latter through a calcium chloride guard tube to a gas absorption trap (Fig. 11,8,1). Heat the mixture in an oil bath at 175-180 for 90 minutes at the end of this period the vigorous evolution of hydrogen chloride will have subsided. Replace the reflux condenser by a fractionating column, distil off the phosphorus oxychloride, and pour the warm residue upon finely crushed ice. Extract the crude sohd pseudo-saccharin chloride with chloroform, dry the chloroform solution with anhydrous magnesium sulphate, and distil off the solvent. Recrystallise the residue from chloroform or from dry benzene. The yield of pine pseudo-saccharin chloride, m.p. 143-145° (decomp.), is 26 g. It is best kept in a sealed glass tube or in a glass-stoppered bottle.  [c.978]

It is usually more convenient to work under an inert-gas atmosphere using Schlenk type apparatus. The principle of Schlenk methods involve a flask/vessel which has a standard ground-glass joint and a sidearm with a tap. The system can be purged by evacuating and flushing with an inert gas (usually nitrogen, or in some cases, argon), repeating the process until the contaminants in the vapour phases have been diminished to acceptable limits. A large range of Schlenk glassware is commercially available (e.g. see Aldrich Chemical Catalog and the associated technical bulletin AL-166). With these, and tailor-made pieces of glassware, inert atmospheres can be maintained during crystallisation, filtration, sublimation and transfer.  [c.30]

When distillation starts, the pig is so placed that the first fraction collects in C. When the second fraction starts to distil, A is rotated slightly to bring the outlet tube leading to D in the lowest position, so that the second fraction collects in D further rotation then causes the third fraction to collect in E. The apparatus however often gives unsatisfactory results, particularly in the hands of students, who frequently find that if a good vacuum is obtained in the apparatus, the pig sticks firmly around the cork F and refuses to rotate conversely, easy rotation around this cork usually means a leaky joint at this point, and an unsatisfactory and varying pressure is recorded by the manometer. (The ground-glass fitting B shown in Fig. 23(F), p. 46, avoids this trouble,)  [c.31]

When distillation starts, the pig is so placed that the first fraction collects in C. When the second fraction starts to distil, A is rotated slightly to bring the outlet tube leading to D in the lowest position, so that the second fraction collects in D further rotation then causes the third fraction to collect in E. The apparatus however often gives unsatisfactory results, particularly in the hands of students, who frequently find that if a good vacuum is obtained in the apparatus, the pig sticks firmly around the cork F and refuses to rotate conversely, easy rotation around this cork usually means a leaky joint at this point, and an unsatisfactory and varying pressure is recorded by the manometer. (The ground-glass fitting B shown in Fig. 23(F), p. 46, avoids this trouble,)  [c.31]

An electrically-heated jacket is easily constructed from two pieces of Pyrex glass tubing of such a length as to extend from the bottom of the head to just above the lower end of the column—the latter may carry a ground joint. The inner tube may be of 35 mm. bore and the outer tube of 55 mm. bore this allows room for the column with attached thermometer inside the inner tube (compare Fig. II, 17, 2). The narrow tube is wound with electric heating tape heat input is controlled by a resistance, energy regulator or a variable transformer. The ends of the jacket are closed with asbestos or other insulating board of convenient size and shape.  [c.96]

With a single receiver tube as shown in Fig. 40 it is necessary to interrupt the distillation each time the receiver is changed. For more precise work a multiple receiver as shown in Fig. 42 should be used. The lower part L of this apparatus contains 6 small collecting tubes C, eachf supported in a wire hoop attached to a fixed vertical glass rod. The receptacle L is attached to the upper part of the apparatus by a ground-in glass joint, J, carefully lubricated by silicone grease. By gently rotating the receptacle L about the ground-glass joint J, it is possible to collect the different fractions in the separate tubes without stopping the distillation, and hence without alteration of pressure.  [c.65]

Apparatus. The apparatus is made of Pyrex glass, in one piece. It consists of a shaped bulb A (Fig. 89 of about 30 ml. capacity in which the reaction takes place, provided with an inclined inlet B at the side and a vertical ascension tube D. B serves not only as an inlet for the admission of the carrier gas but also as the route by which the reagents and test sample are introduced into the apparatus. B ends in a small ground-glass joint into which fits ajoint carrying a capillary-tube which projects well down into the bulb A (the end of the capillary should be just above the liquid level when the apparatus is charged for the determination). The upper extension of this capillary beyond the joint is provided with a tap C to control the rate of flow of the carrier gas.  [c.498]

The test sample is now weighed out. This is best done by weighing 20-25 mg. into a small tinfoil cup (the cup is best made by cutting the corners off a small square of tinfoil, and then pressing this circle into a cup by rubbing it into shape round the end of a glass rod). After the material has been introduced, the cup should be gently tapped on a metal block, while held with balance tweezers, to ensure that no particles of the sample are adhering to its outside edge this also serves to settle the material down on to the floor of the cup. The cup, after weighing, is lightly dosed by pinching the edges together and then slid carefully down the side-arm B into the reaction vessel A. For many substances it is quite satisfactory to weigh the material on a small square of cigarette paper (any gummed edge being cut off), which is finally folded over as before. If this is done, however, it is necessary to introduce a few mmute pieces of unglazed porcelain into A in order to promote smooth boiling. With the tin cup this is unnecessary, as the stannic iodide produced by the dissolution of the cup promotes steady boiling and prevents bumping. About 20 mg. of pure phenol are then added. Finally 5 ml. of hydriodic acid M.A.R. grade, d 1 7, are added from a pipette, the end of which should be inserted well into vessel A, and care taken in withdrawal so that no hydrogen iodide is left in the side-arm B. The ground-glass joint is now inserted into the side-arm and the rubber tube from the Kipp and wash-bottle attached. The tap C is now fully closed and the Kipp tap opened. Tap C is now very carefully opened until carbon dioxide begins to pass and adjusted so that not more than two bubbles are rising round the spiral in the receiver K at one time. It is very important to ensure at this stage that the rate is quite satisfactory, as too rapid a flow will almost certainly result in some methyl iodide escaping absorption. Finally a very slow stream of water is allowed to flow through the condenser E.  [c.499]

The test sample is now weighed out. This is best done by weighing 20-25 mg. into a small tinfoil cup (the cup is best made by cutting the corners off a small square of tinfoil, and then pressing this circle into a cup by rubbing it into shape round the end of a glass rod). After the material has been introduced, the cup should be gently tapped on a metal block, while held with balance tweezers, to ensure that no particles of the sample are adhering to its outside edge tliis also serves to settle the material down on to the floor of the cup. The cup, after weighing, is lightly closed by pinching the edges together and then slid carefully down the side-arm B into the reaction vessel A. For many substances it is quite satisfactory to weigh the material on a small square of cigarette paper (any gummed edge being cut off), which is finally folded over as before. If this is done, however, it is necessary to introduce a few minute pieces of unglazed porcelain into A in order to promote smooth boiling. With the tin cup this is unnecessary, as the stannic iodide produced by the dissolution of the cup promotes steady boiling and prevents bumping. About 20 mg. of pure phenol are then added. Finally 5 ml. of hydriodic acid M.A.R. grade, d i-y, are added from a pipette, the end of which should be inserted well into vessel A, and care taken in withdrawal so that no hydrogen iodide is left in the side-arm B. The ground-glass joint is now inserted into the side-arm and the rubber tube from the Kipp and wash-bottle attached. The tap C is now fully closed and the Kipp tap opened. Tap C is now very carefully opened until carbon dioxide begins to pass and adjusted so that not more than two bubbles are rising round the spiral in the receiver K at one time. It is very important to ensure at this stage that the rate is quite satisfactory, as too rapid a flow will almost certainly result in some methyl iodide escaping absorption. Finally a very slow stream of water is allowed to flow through the condenser E.  [c.500]

With a single receiver tube as shown in Fig. 40 it is necessary to interrupt the distillation each time the receiver is changed. For more precise work a multiple receiver as shown in Fig. 42 should be used. The lower part L of this apparatus contains 6 small collecting tubes C, eachf supported in a wire hoop attached to a fixed vertical glass rod. The receptacle L is attached to the upper part of the apparatus by a ground-in glass joint, J, carefully lubricated by silicone grease. By gently rotating the receptacle L about the ground-glass joint J, it is possible to collect the different fractions in the separate tubes without stopping the distillation, and hence without alteration of pressure.  [c.65]

The type of carbon dioxide absorption tube S (Fig. 85) which is recommended is shown in detail in Fig. 86. In this tube the composite filling of soda-lime and a small packing of magnesium perchlorate are kept in separate chambers which are a-put in contact only while gas is flowing, by rotating a ground-glass joint tap T, which divides the tube into two compartments the perchlorate being packed in what is virtually an enlarged hollow tap-stopper a (Fig. 86) at one end of the tube. By keeping these two elements of tube-packing out of contact 1 with each other except when the tube is being used to absorb carbon dioxide, the "life of thetube, before repacking becomes necessary, is much increased. In filling the carbon dioxide absorption tube S of this type (Fig 86), the hollow stopper y  [c.471]

Apparatus. The apparatus is made of Pyrex glass, in one piece. It consists of a shaped bulb A (Fig. 89) of about 30 ml. capacity in which the reaction takes place, provided with an inclined inlet B at the side and a vertical ascension tube D. B serves not only as an inlet for the admission of the carrier gas but also as the route by which the reagents and test sample are introduced into the apparatus. B ends in a small ground-glass joint into which fits a joint carrying a capillary-tube which projects well down into the bulb A (the end of the capillary should be just above the liquid level when the apparatus is charged for the determination). The upper extension of this capillary beyond the joint is provided with a tap C to control the rate of flow of the carrier gas.  [c.498]

The test sample is now weighed out. This is best done by weighing 20-25 mg. into a small tinfoil cup (the cup is best made by cutting the corners off a small square of tinfoil, and then pressing this circle into a cup by rubbing it into shape round the end of a glass rod). After the material has been introduced, the cup should be gently tapped on a metal block, while held with balance tweezers, to ensure that no particles of the sample are adhering to its outside edge this also serves to settle the material down on to the floor of the cup. The cup, after weighing, is lightly closed by pinching the edges together and then slid carefully down the side-arm B into the reaction vessel A. For many substances it is quite satisfactory to weigh the material on a small square of cigarette paper (any gummed edge being cut off), which is finally folded over as before. If this is done, however, it is necessary to introduce a few mmute pieces of unglazed porcelain into A in order to promote smooth boiling. With the tin cup this is unnecessary, as the stannic iodide produced by the dissolution of the cup promotes steady boiling and prevents bumping. About 20 mg. of pure phenol are then added. Finally 5 ml. of hydriodic acid M.A.R. grade, d 1-7, are added from a pipette, the end of which should be inserted well into vessel A, and care taken in withdrawal so that no hydrogen iodide is left in the side-arm B. The ground-glass joint is now inserted into the side-arm and the rubber tube from the Kipp and wash-bottle attached. The tap C is now fuUy closed and the Kipp tap opened. Tap C is now very carefully opened until carbon dioxide begins to pass and adjusted so that not more than two bubbles are rising round the spiral in the receiver K at one time. It is very important to ensure at this stage that the rate is quite satisfactory, as too rapid a flow will almost certainly result in some methyl iodide escaping absorption. Finally a very slow stream of water is allowed to flow through the condenser E.  [c.499]

The test sample is now weighed out. This is best done by weighing 20-25 mg. into a small tinfoil cup (the cup is best made by cutting the corners off a small square of tinfoil, and then pressing this circle into a cup by rubbing it into shape round the end of a glass rod). After the material has been introduced, the cup should be gently tapped on a metal block, while held with balance tweezers, to ensure that no particles of the sample are adhering to its outside edge this also serves to settle the material down on to the floor of the cup. The cup, after weighing, is lightly closed by pinching the edges together and then slid carefully down the side-arm B into the reaction vessel A. For many substances it is quite satisfactory to weigh the material on a small square of cigarette paper (any gummed edge being cut off), which is finally folded over as before. If this is done, however, it is necessary to introduce a few minute pieces of unglazed porcelain into A in order to promote smooth boiling. With the tin cup this is unnecessary, as the stannic iodide produced by the dissolution of the cup promotes steady boiling and prevents bumping. About 20 mg. of pure phenol are then added. Finally 5 ml. of hydriodic acid M.A.R. grade, d ry, are added from a pipette, the end of which should be inserted well into vessel A, and care taken in withdrawal so that no hydrogen iodide is left in the side-arm B. The ground-glass joint is now inserted into the side-arm and the rubber tube from the Kipp and wash-bottle attached. The tap C is now fully closed and the Kipp tap opened. Tap C is now very carefully opened until carbon dioxide begins to pass and adjusted so that not more than two bubbles are rising round the spiral in the receiver K at one time. It is very important to ensure at this stage that the rate is quite satisfactory, as too rapid a flow will almost certainly result in some methyl iodide escaping absorption. Finally a very slow stream of water is allowed to flow through the condenser E.  [c.500]

The manometer D is connected with impregnated pressure-tubing, and by a glass-to-glass joint, with the side-arm F of a U -tube (each limb being about i cm. in diameter and 12 cm. long). Before filling, the U-tube should be washed with distilled water, alcohol, then ether and finally dried in an oven. The first limb of the U-tube contains soda-lime (B.D.H. Micro-analytical reagent grade Carbasorb is very convenient) whose purpose is to remove any carbon dioxide from the oxygen stream. A drawback of the soda-lime is that it readily takes up water vapour (a little comes from the pressure gauge) becoming first sticky and then forming a hard impermeable crust that greatly slows the oxj gen stream. This difficulty may be overcome by putting a small quantity of magnesium perchlorate (Anhydrone—M.A.R. grade) in the top of the U-tube limb this also absorbs water, but tends to contract as it does so, drawing away from the wall of the tube and hence not impeding the oxygen flow. Thus in filling the U-tube a small plug of glass wool is put at the bottom ofthe limb, the limb two-thirds filled with soda-lime, a further plug of glass wool inserted, the top third of the tube filled with magnesium perchlorate and topped with a plug of glass wool that comes just opposite the side-arm. The open end of the limb which projects (5 cm.) above the side-arm is then sealed off. Sealing off the limb has been found to be most satisfactoiy, as stoppers, taps, e/c., tend to leak or to give other trouble. (Glass stoppers, each previously ground to fit its own neck, are reasonably satisfactoiy if carefully sealed with glass cement for subsequent recharging, the cement is softened by warming and the stopper released.) After being used  [c.468]

The manometer D is connected with impregnated pressure-tubing, and by a glass-to-glass joint, with the side-arm F of a U -tube (each limb being about i cm. in diameter and i2 cm. long). Before filling, the U-tube should be washed with distilled water, alcohol, then ether and finally dried in an oven. The first limb of the U-tube contains soda-lime (B.D.H. Micro-analytical reagent grade Carbasorb is very convenient) whose purpose is to remove any carbon dioxide from the oxygen stream. A drawback of the soda-lime is that it readily takes up water vapour (a little comes from the pressure gauge) becoming first sticky and then forming a hard impermeable crust that greatly slows the oxygen stream. This difficulty may be overcome by putting a small quantity of magnesium perchlorate (Anhydrone—M.A.R. grade) in the top of the U-tube limb this also absorbs water, but tends to contract as it does so, drawing away from the wall of the tube and hence not impeding the oxygen flow. Thus in filling the U-tube a small plug of glass wool is put at the bottom of the limb, the limb two-thirds filled w ith soda-lime, a further plug of glass wool inserted, the top third of the tube filled with magnesium perchlorate and topped with a plug of glass wool that comes just opposite the side-arm. The open end of the limb which projects (5 cm.) above the side-arm is then sealed off. Sealing off the limb has been found to be most satisfactory, as stoppers, taps, etc., tend to leak or to give other trouble. (Glass stoppers, each pre% iously ground to fit its own neck, are reasonably satisfactoiy if carefully sealed with glass cement for subsequent recharging, the cement is softened by warming and the stopper released.) After being used  [c.468]

PreUminary Operations.—Grind up a little pure oxalic acid and carefully weigh out o i5 to o 2 gram (not more) in the boat Weic h also the calcium chloride tube and potash apparatus uithout stoppers or other accessories. The side tube of the calcium chloride tube, which carries the bulb, is attached directly to the combustion tube with a rubber cork. This cork should be carefully selected, and should e.xactly fit the combustion tube. The bore hole should be small and smooth, and it is advisable to dust it with graphite or coat it with a film of vaseline to prevent the rubber from clinging to the glass, a matter of frequent occurrence unless this precaution is taken. The cork should be kept exclusively for the combustion. Push the side tube of the calcium chloride tube through the hole until it is flush with the opposite surface, and squeeze the cork tightly into the combustion tube. Attach the potash apparatus to the other limb of the calcium chloride tube by a well-fitting piece of rubber tubing about 3 cm. (i in.) long, and bring the ends of the glass as closely as possible together. It should be unnecessary to wind wire round the joint if the rubber is of the right diameter. A little vaseline may be used here with advantage, but only in the thinnest film. The potash apparatus will require to be supported upon a block or stand. Remove the copper spiral from the back of the tube. Introduce the boat and push it into position against the asbestos plug by means of the spiral which is placed behind it. Replace the rubber cork connected with the drying apparatus. The apparatus will present the appearance shown in Fig. 10.  [c.8]


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