Carius tubes

Carius tube A thick-walled glass lube originally used in the Carius method but used in any reaction involving volatile materials. 

A practical demonstration of the preparation and sealing of Carius tubes is of vastly greater value than any written description. 

Meanwhile, the organic compound can be prepared for analysis whilst the sealed end C (Fig. 72) of the Carius tube has been cooling dow n. For this purpose, thoroughly clean and dry a small tube, which is about 6 cm. long and 8-10 mm. w ide. Weigh it carefully, supporting it on the balance pan either by means of a small stand of aluminium foil, or by a short section of a perforated rubber stopper (Fig. 73 (A) and (B) respectively) alternatively the tube may be placed in a small beaker on the balance pan, or suspended above the pan by a small hooked wire girdle. 

Place in the tube sufficient organic compound to give subsequently about 0-3 g. of the silver halide, and weigh again. Now allow the small tube to slide carefully down the inclined Carius tube until it finally adopts the position shown in D (Fig. 72). If the compound readily loses halogen in the presence of nitric fumes, the Carius tube should first be rotated in an oblique position to wet the tube for about 10 cm. from the bottom the small tube, if cautiously inserted into the Carius tube, will now come to rest when it first reaches the wet portion of the tube and will thus be held above the main bulk of the acid until the tube is sealed. 

Now roll up the Carius tube (while still in a vertical position) in a strip of ordinary thick drying paper, and then place it in the heavy iron protector tube if the Carius tube is too short and tends to disappear within the iron tube, a short section of old glass tubing should first be placed in the iron tube so that the capillary of the Carius tube just projects. The function of the paper is to protect the Carius tubing from being scratched, and also (more important) to prevent the local overheating which would otherwise occur at places where the Carius tube is in direct contact with the iron tube. The sealed tube, throughout its manipulation, should be left as nearly vertical as possible, so that the contents do not leave the rounded end. 

The furnace (Fig. 74) consists primarily of an iron box A, having 3 or 4 tubes (e.g., B) arranged in a horizontal row, and dipping slightly from the open (left-hand) to the closed (right-hand) end. The top, which usually forms a loose lid to the rest of A, carries a thermometer T, and care should be taken to ensure that the bulb of the thermometer is not touching any part of the metal box. The Carius tube encased in... 

Liquid sulphur compounds should be weighed and introduced into the Carius tube by precisely the same methods as those described for liquid halogen compounds (p. 442). 

A glass dropping-tube E, for the introduction of the nitric acid, is made with a small bulb just above the lower end, so that w ith care it can be withdratvn without the nitric acid coming in contact with the w-alls of the Carius tube. 

Filling and sealing the Carius tube. Introduce 100-150 mg. of powdered silver nitrate into the Carius tube, either through a spill of filter -paper rolled and inserted as described on p.418, or through a small funnel, so that the powder falls freely to the bottom of the tube and does not touch or adhere to the walls. 

Insert the tube E to within 1 inch of the bottom of the Carius tube, open the tap slightly, and allow the acid (about 10 drops) to run in. Then withdraw the dropping-tube, taking great care that traces of nitric acid are not deposited on the upper sides of the tul. ... 

Now fit the weighed funnel G again to the filter-flask, and attach the Pregl filter-tube K as shown (Fig. 21). Apply 2i gentle suction from the water-pump, and dip the open limb of the tube K just below the surface of the liquid in the Carius tube. Draw off the supernatant liquid a little at a time until rather less than 1 ml. remains. Now gently shake the mixture in the Carius tube, and try to adjust the suction so... 

Tubes for sealed tube reactions, such as the Carius determination of halogens and sulphur, can be made from Pyrex, Monax or soda glass. The mechanical strength of the glasses is about the same, but a soda Carius tube is much more likely to crack as a result of thermal strain than a Pyrex or Monax one. The Carius tubes are usually made from tubing of approximately 20-25 mm diameter and 3 mm wall thickness—Pyrex extra heavy tubing of external diameter 22 mm has a wall thickness of 2-5-4 mm and can be used up to 600°C. 

The rhodium powder was prepared directly in the Carius tube employed for the hydrosilylation experiment. 

The compounds benzonitrile, p-methylbenzonitrile, /)-methoxybenzonitrile, p-trifluoromethyl-benzonitrile, /)-methoxycarbonylbenzonitrile, and triethoxysilane are commercial products and are degassed and stored under argon before use. Trimethylsilane was prepared according to a literature report [38]. The nitrile (9.8 mmol) and the hydrosilane (49 mmol) are added to the rhodium catalyst (0.1 mmol) contained in a Carius tube. When using trimethylsilane, the operation is performed at —20°C. The tube is closed and the mixture stirred at 100 °C for 15h. The liquid is separated by filtration and the excess of hydrosilane removed under vacuum to leave the N, Wdisilylamine derivative. If necessary, a bulb to bulb distillation is performed to obtain a completely colorless liquid. The yields obtained in the different runs are reported in Table 6. The product have been characterized by elemental analysis, NMR spectroscopy, and GC-MS analysis. 

In spite of extensive cooling and precautions, a mixture of methyl azide, methanol and dimethyl malonate exploded violently while being sealed into a Carius tube. The vapour of the azide is very easily initiated by heat, even at low concentrations. 

The solid exploded on heating, and an aqueous solution sealed into a Carius tube exploded violently when the tube was cracked open with a red-hot glass rod. (The aci-salt may have been formed). 

The scale of the procedure described for preparing [octamethyltetrabenzoporphi-nato (2—)]cobalt(II) by heating the reagents in an evacuated Carius tube at 390°C must not be increased or the tube will explode. Personal protection is also necessary when opening the sealed tube. 

Preparing the Carius Tube.—First clean the tube with bichro-... 

According to the amount of substance taken add 60-90 mg. of finely powdered silver nitrate (it is best to add one and a half times the amount which corresponds to the expected halogen content). Then, if the substance is only slowly attacked by nitric acid in the cold, add 10-1-5 c.c. of red fuming nitric acid. In the case of substances which react vigorously with nitric acid in the cold, hold the Carius tube obliquely and add the acid in a small round-bottomed tube (length 6 cm., width 0-8 cm.), cautiously allowing it to slide to the bottom of the Carius tube and taking care that substance and acid do not come into contact with each other. 

Clean the outside of the tube and cautiously dilute the contents with 10 c.c. of water. The small tube which contained the nitric acid rises to the surface. Grasp this tube with a pair of bone-tipped forceps, empty its contents into a beaker having a rounded bottom (depth 15 cm., width 3-3-5 cm.), and wash with distilled water. Break up the silver halide as much as possible with a glass rod and transfer the contents of the Carius tube quantitatively to the beaker, washing out repeatedly. With a glass rod remove any silver halide... 

A solution of 0.54 g. (2 mmoles) of ferric chloride hexahydrate and 0.33 g. (3 mmoles) of diethylammonium chloride (Note 1) in 5 g. of methanol is added to a solution of 11.2 g. (0.1 mole) of 1-octene (Note 2) and 0.42 g. (2 mmoles) of benzoin (Note 3) in 36 g. (0.3 mole) of chloroform (Note 4). The resulting homogeneous mixture is introduced into a Carius tube of about 100-ml. capacity. Air is displaced by dropping a few pieces of dry ice into the tube (Note 5). The tube is sealed (Note 6), heated to 130°, kept at that temperature for 15 hours, cooled to room temperature (Note 7), and opened. The contents of the tube are transferred to a separatory fuimel, and the tube is rinsed with about 10 ml. of chloroform. The reaction mixture is washed with 40 ml. of water. The aqueous solution is extracted with 10 ml. of chloroform, and the extract is added to the original chloroform layer. Solvent is distilled at atmospheric pressure (bath temperature up to 130°). The distillation flask is allowed to cool, and distillation is continued at 25 mm. (bath temperature up to 120°) (Note 8). The flask is cooled again, and distillation is continued to dryness at 0.1 mm. (bath temperature up tc 150°), giving crude l,l,3-trichloro- -nonane (19.4 g.) as a yellow oil, b.p. 60-85° (0.1 mm.), 1.4650. The purity of this... 

The Carius tube has a short piece (about 4 in.) of heavy-walled tube (8-mm. external diameter) sealed to it. This greatly facilitates subsequent sealing and re-use of the tube. The solution is introduced by means of a funnel with a drawn-out stem. 

Carius tube reaction of [Cr(CO)(,] and the appropriate ligand at 140°C for 14 h. The conformational inversion of the five-membered ring has been studied by n.m.r. and some of the complexes have been shown to exhibit marked conformational preferences. ... 

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