Safety tube

Steam generator. For small scale work the steam generator D, Fig. 15, p. 33) is too cumbersome for the production of a small amount of steam. It is preferable to use a 250 ml. conical flask fitted with cork containing a vertical safety tube and an outlet-tube (Fig. 44). Care should be taken that the length of rubber tubing connecting the steam oudet tube to the flask containing the materi to be distilled should be as short as possible and should not contain kinks. 

Alternatively, a flask (capacity one litre or more), fitted with a two-holed cork carrying a long safety tube and a short right-angled bend, may be used. A large distilling flask will serve the same purpose. 

Steam distillation.—For small quantities of compounds, which are readily volatile in steam, water may be added to the contents of the reaction flask (e.g. Figs. XII, 2,4 and XII, 2, 11) and the flask heated in an air bath or with a small flame. Alternatively, if preferred, steam may be passed into the reaction flask from a separate generator this may consist of a small conical flask provided with the usual safety tube (compare Fig. II, 40, 1). 

The crude liquid acid (about 300 g.) is cooled with running water and 15 cc. of concentrated sulfuric acid is added the clear yellow oil becomes cloudy. The acid is esterified by the method described in Org. Syn. 3, 54, with the following changes all three flasks, the alcohol flask, the trap, and the esterification flask are i-l. round-bottom wide-neck flasks. The alcohol flask and the trap are set on adjacent steam baths. The esterification flask is placed in an oil bath which is heated by a free flame. A safety tube leads from the alcohol flask and dips under 7.5 cm. of mercury contained in a side-arm tube. 

If it is necessary to generate the steam from a can or similar contrivance, the steam generator should be connected with a safety tube dipping under 20-25 cm. of mercury. 

Use burner connector safety tubing to connect the Bunsen burner to the gas inlet. Make sure the hose does not have any cracks or holes. 

A 500-ml. three-necked round-bottomed flask is fitted with an efficient reflux condenser, a glycerol-sealed mechanical stirrer,1 a dropping funnel, and a gas inlet tube extending nearly to the blades of the stirrer (Note 1). An absorption train,2 with the addition in / of a safety tube which extends nearly to the bottom, is connected to the upper end of the reflux condenser (Note 2). A 2-cm. layer of water in J allows it to serve as a bubble counter K is one-third filled with a 50% potassium hydroxide solution. The entire apparatus is set up in subdued light in a hood and swept with dry hydrogen (Notes 3 and 4). Phenyl-magnesium bromide is prepared in the flask by the usual procedure 3 from 78.5 g. (0.5 mole) of bromobenzene, 12 g. (0.5 gram... 

In order to remove alcohol and ether the gas is passed through a wash-bottle containing concentrated sulphuric acid,1 and sulphurous acid is removed in a three-necked wash-bottle2 containing 42V-8odiuin hydroxide and provided with a safety tube (Fig. 50). 

To the reaction mixture is added 15 cc. of concentrated sulfuric acid and the flask is placed in an oil bath connections are made to the rest of the apparatus and heating is commenced. About 70 cc. of alcohol will distil over before the temperature of the mixture reaches no°. Meanwhile, 600 cc. of 95 per cent ethyl alcohol is placed in the i-l. flask. As soon as the temperature reaches 110° this alcohol is boiled so that a rapid stream of vapor passes into the reaction mixture—the temperature should remain at no°. More alcohol is added to that in the i-l. flask until 800 cc. has been added heating is continued until all has been vaporized, whereupon the safety tube is opened at once. The flask is removed from the oil bath and allowed to cool. This esterification takes about three hours. The distillate obtained during the process consists of dilute alcohol. 

Through the latter pass (1) A glass tube about 4 nun. wide drawn out at the bottom to 1 mm., this reaching into the liquid and almost to the bottom of the flask this tube is connected with a steam generator or a flask fitted with a safety tube containing at least a litre of water (2) another tube provided with a safety bulb and connected with a condenser leading to a flask of about 300 c.c. capacity with a mark at 200 c.c. 

Why must the hydrochloric acid gas be passed through a washing bottle Why is the safety tube necessary ... 

If the steam is taken from a steam line, it is advisable to insert, between the line and the distillation flask, a safety flask fitted with a vertical tube. This safety flask serves both to collect the condensed water carried along with the steam and to permit control of the pressure (2, in Fig. 23a, page 141). If the steam is produced in the laboratory, the steam kettle is provided with a safety tube. 

Fig. 23. (a) Laboratory apparatus for distilling with superheated steam 1, steam generator 2, water trap with vertical safety tube 3, superheater 4, distillation vessel in oil bath 5, condenser with wide tube 6, device for pushing out solid material collecting in the condenser 7, receiver for distillate 8, gas line 9, cooling water. 

Apparatus The generator is shown in Fig. 30. A is a. 500 cc. flask provided with a two-hole rubber stopper. is a safety tube. C is the double right angle bend which was made in Exp. 2. D is a rubber connector about 4 cm. long. E is a delivery tube of such length that its end is level with the bottom of the flask. 

P ocess Pour slowly but continuously through the safety tube enough (about 50 cc.) dilute sulphuric acid upon at least 25 gm. of granulated zinc to produce a steady current of hydrogen gas for about eight minutes. It is advisable to use considerable zinc and a moderate amount of acid. Acid must not be added after the evolution of gas begins, unless, of course, the experiment is begun anew. Let... 

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