1. The seal for the mechanical stirrer used (
.htmFig. 10) is made from two one-hole
rubber stoppers and a piece of glass tubing with
glycerin as a seal and lubricant. According to the submitters, it is better than a
mercury seal, not only for reactions where halogens, halogen acids, or compounds that react with
mercury are present, but also for practically any other reaction since the handling of
mercury always requires a considerable amount of care.
The glass tubing
D, about 10 cm. in length, is just large enough in diameter to permit the stirrer
E to rotate freely. The smaller of the two one-hole rubber stoppers,
A, is bored to a depth of about 7 mm. with a cork-borer whose diameter is approximately 3 mm. larger than that of tubing
D, and then this section is cut out with a pair of scissors. Rubber stopper
B is 10–15 mm. larger in diameter than
A. When assembled, tubing
D fits tightly in rubber stopper
B, and protrudes out at the top about 4 mm., and rubber stopper
A fits tightly about stirrer
E and rests on top of rubber stopper
B.
Glycerol is used as a seal and as a lubricant between the contact surfaces of rubber stoppers
A and
B, and the portion of tubing
D protruding out of rubber stopper
B acts as a wall in preventing
glycerol from flowing down inside the tubing. When the stirrer motor is on, rubber stopper
A rotates with stirrer
E. Rubber stopper
C fits tightly over tubing
D and in the mouth of the reaction flask.
2. When the preparation is carried out in larger quantities, evolution of heat accompanies the mixing of
iodine and
thiophene, and unless the mixture is stirred well, it will solidify into a hard mass. By keeping the quantities reasonably small, this tendency to solidify is reduced to a minimum.