A SMALL, COMPACT OZONIZER FOR LABORATORY USE
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THOMAS P. WHALEYL University of Kansas, Lawrence, Kansas
OZONE
has long been recognized as an excellent tool for determining the positions of double bonds in nusaturated organic compounds, and is finding increasingly greater usefulness as an oxidant in preparing higher oxidation states of metals and in synthesizing organic compounds. Most commercial machines de-
signed for large ozone output are rather large and costly. Ozonizers with maximum output have been described in the literature2 b u t most are of complicat,ed design or are too large for use inside small hoods. The simpler ozonizers described in the literature3 tend to sacrifice ozone output for compactness and simplicity of design. The apparatus described below is designed specifically to produce a relatively high percentage ozone output a t a minimum cash outlay and a minimum space requirement. Ozone production in a silent-electrical discharge type ozonizer is greatly affected by the type of glass which comes in contact vith the oxygen (soft glass is best), and the temperature (Thorp and Armstrong4found that the output a t -55°C. is approximately three times that obtained a t room temperature). The percentage output can be increased by connecting several ozonizer tuhes in series to increase the electrode area. CONSTRUCTION O F APPARATUS
The individual ozonizer tubes mere constructed of soft glass. The inner tube was 12 mm. O.D., the outer, 22 mm. O.D., and the outlets were 8 mm. O.D. A somewhat larger size tubing must he used for the inner tube if the secondary voltage of the transformer employed is less than 8000 volts. The seal of inner to outer tubes should be as close as possible to the inlet in order that maximum electrode area may he obtained. The container which holds the ozonizer tubes mas
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Present address: Ethyl Corporation, Baton Rouge, Louisiana. BOER,H . , Rev. Ira". ehim., 70, 1020-32 (1951). a SHEEAAN, W., AXD W. CARMODY, I d Eng. Chem., Anal. Ed., 9 , 8 (1937); G ~ o e s ,M. J. A N D M. PHILLIPS,J. ASSOC.A ~ T . Chem., 21, 326-31 (1938); UHRIC,K., J . CHEM.EDUC.,22, 582 (19451. ,-
Laboratory
Ozonizer
' THORP,C . E., AND W. J. ARMSTROCG, The Frontze~.9, No. 2, 3-5, 16-17 (1946).
JOURNAL OF CHEMICAL EDUCATION
constructed of 74-mm. O.D. Pyrex tubing, 21 cm. in length and slightly flared at the top. A 600-ml. Berzelius beaker is adequate for this purpose but is smaller and, consequently, permits less electrode area. The three ozonizer tubes were held in place by a support cut from a clay plate on the bottom of the container. If a noncorrosive material is to be used as an electrode, this support may be conveniently constructed from a large rubber stopper. The support at the top was made of '/8-inch plywood, shaped to fit the flared top of the container, designed to maintain the tubes in a vertical position. When the ozonizer tubes were in place, the top support was firmly fastened t o the Pyrex container by means of friction tape. The tubes were connected in series by means of Tygon tubing; both Pyrex container and inner types were filled with 7.7 M zinc chloride solntion; and copper wires leading from the secondary of the transformer were permitted to dip into the electrode solution. The inner electrode may be mercury, or any type of electrolytic conductor which will not freeze a t the temperature of the cooling bath. The ozonizer was then placed in a 2000-ml. Dewar vessel which contained
VOLUME 34, NO. 2, FEBRUARY, 1957
a suitable cooling bath, supported at the top by a cork ring. The cork ring was fitted with an opening to permit addition of solid carbon dioxide if the temperature became too high during ozouization. The transformer nsed was a war-surplus navy trausformer, capable of 10,800 volts secondary voltage when operating at a primary voltage of 115 volts. Discharge between electrodes did not take place a t voltages less than 8000 volts. A variable transformer was nsed t o regulate the voltage, and the lines leading to the primary of the transformer contained 2-ampere fuses. This ozonizer, while taking up no more space than a 2000-ml. Dewar vessel and only 26.5 cm. in height, consistently produced between 7.5% and 8.0% (by weight) ozone at a temperature of -40°C. and a 60-cycle voltage of 10,500 volts. Tank oxygen, carefully dried by passage through magnesium perchlorate, was passed through the apparatus at a flow rate of 5 to 6 liters per hour. Lower percentage conversion was obtained at faster flow rates. The conversion may be increased by maintaining the temperature somewhat lower than -40°C. and also by using voltage of greater frequency.
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