ANALYTICAL EDITION
Septemhsr, 1945
placed on the rod. The authors' model was driven hy a 0.125-h.p. motor, operating at 1525 r.o.m.. connected with B 40 to I reducine eear. The pulley on the ;educing gear was p l a d below the &ley on the shaft of the apparatus, and the connecting belt kept taut hy allowin= Dart of the weieht of the motor and reas to hane from the belt. TI% bearing at thz end of the Pyrex rGd which e&sists of sheet asbestos lubricated with graphite supports most of this weight. When anhvdrous aluminum ohldidc. nhosnhorus oentachloride. and sodiu& carbonate were used thk'sysiem al&ya operated smoothly with no tendency to stick. I
601
aluminum chloride per minute. *? .^
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(1) Dennis. L.M., and Anderson, R.P..J . Am. C h . Sm.,36,882 (1914). (2) Fi&-L., "Experiments in Organic Chemistry". 2nd ed.. Part 11, p. 311, New York. D. C. Hseth and Go.. 1941. (3) A.. and Guttmann. 0..B e . . 37.m y15 (1904). , ~Stork. , (4) webster, 5.H., and D&kii,'L. ni... I . Am. Chon. Sm..55, 3234 (1933). ~~~~
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All-Glass ! ROBERT P. > American Smelting & Refining Company, Cenb
IN
A recent article ( 1 ) an all-glass stirrer wss pictured which is compact, inexpensive, easy to construct, and eliminates the danger of contamination of the solution by corrosion products from an electric motor. The device is not suitable for agitation of large volumes, nor of heavy viscous liquids,'but is extremely useful for sgitation of volumes such as are constantly used in analytical work. I n electrometric titrations the electrodes may he attached to the stirrer, thus eliminating the cluttered condition normally encountered in eleetrometric operations. A method of attaching eleotrodes is shown in Figure 1.
The small T which furnishes the wer to drive the shaft, is connected to it kith a Bhort length oi%bber tubing, which mmes as universd joint, to abeorh stresses due to a r m a t e shaft alignment, makes disassembly Dwihle. and mitS au to lets thmu h the hole in the cente;. T i g k or bind ing bearings will not o rate, but alight high spots may be q,iicklv eraund t o fit. g o ereat clearance results in air leak+l e wi-th-poor performance.
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Figure 9.
Diagram
Stator. A . 14-mm.tubing 11cm. Ions. 8. 8-mm. tubin.. 7 ck 8 cm. Figure 1.
All-Clan Stirrer
Stirrers of the type described are available commeroidy but cannot be disassembled for cleaning or lubricating. Foreign particles, particularly rust scale, may came through air lines and lodge between bearings and shafts, seriously affecting the efficiency of operation. Oeeasionally broken parts cannot be replaced on commercid stirrers. The stirrer is an airdriven type operating on low prmure (not over 10 pounds) on the pinwheel or rocket principle (Figure 2). The stator is a T-tube fitted with rubber stoppers which are bored to accommodate g l w bearings. The rotor is in two parts.
lubricated with a droo of mediwn oil before 88semhly and ocoasionally thereafter. Oil of S;A.E. 30-40 is satisfactory. When the unit is aasembled, stoppers should be adjusted by rotating until minimum bind and friction are obtained and the shaft turns freely. A p r o p e r l y digned stirrer should turn when blown by mouth. T h e d a n g e r of t h e rotor's d i s i n t e g r a t i n g while in operation is extremely remote. Dozens of these stirrers have been made and wed in this laboratory under d l kinds of conditions. The only breakage encountered has been in electrometric titrations, where the rotor has been shattered hy contact with the buret. To prevent this, smell pieces of rubber tubing extanding slightly beyond the ends of the rotor, and with hales eorrespouding to bole locatioas in the rotor, may be installed. LITERATURE CITED
R. P..and Ziechkau, 0. C.. im. ENO. Carnu.. ANAL ED.. 15. 281 (1943).
(1) Yeok.
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