The
NEWin CPI Equipment
ITEM OF THE MONTH Portable Instrument Measures Ozone Concentrations • • • • •
Accurately Continuously Permanently Economically Remotely
A specter is in the land! He is small, but so is a pound of U235· This tiny but powerful and obnox ious enemy is the ozone molecule, 0 3 , which does not need much help from other ozone molecules to make things unpleasant for all unlucky enough to make contact with him. So small, in fact, are his numbers, that ozone is measured in parts per hundred million parts of air (p.p.h.m.). Obviously, the analyti cal methods for determining such small amounts of ozone call for bulky and costly equipment in order to fish a little analyzablc material from a lot of air. All ear lier techniques called for an expen sive piece of equipment and consid erable man power for anything ap proaching a suitably accurate anal ysis. The Mast Development Co. of Davenport, Iowa, no stranger to the business of ozone determinations, has completed the development of a bantam-weight portable which eliminates many of the inconven iences which go along with accurate ozone analysis, especially when ozone concentration is low. Mast designates this instrument as the MDC Model 725-3B Portable Ozone Recorder. An instrument combining com pactness, light weight, and porta bility can hardly hope to be other than a real boon to a great number 80 A
Ozone concentrations are accurately measured and continuously recorded even at remote distances with the Mast model 725-3B
of interested parties. In air pollu tion studies, for instance, where ozone plays a large part in material corrosion and human irritation, analyses are needed rapidly and ac curately. Industrial hygienists are expected to take advantage of the Mast midget for obvious reasons, while growers of above-ground fruit and vegetables find that the ap pearance and quality of their prod uce is affected by small amounts of ozone. Probably the most ob vious effect of ozone is that of rub ber deterioration. As little as 5 p.p.h.m. of ozone in air causes hoses, tire sidewalls, weatherstripping, and other rubber goods to crack in an unreasonably short length of time. Concentrations of ozone can be controlled in test cabinets in elastomer evaluation when moni tored with MDC'S new innovation. Model 725-3B represents an ulti mate in ozone sensing technique at the present stage of the art. With the operation based on a highly ef ficient Micro-Coulomb Ozone Sen sor, the instrument offers many features of worth, not the least of
which is remote control—readings may be recorded as much as a quarter of a mile away from the test area. The sensing meter is supported in operation by several basic compo nents. A chemical solution, con taining the proper amounts of sens ing reagents, is metered into the sensor from a solution supply tube. The solution flows in a fine film down the electrode support, upon which are wound many turns of a fire wire cathode and a single turn of a wire anode and is deposited in the waste reservoir. As an air sam ple enters the meter, it is pumped through the sensor from a narrow annulus, where it comes into inti mate contact with the solution con tained of the electrode, then exits from the machine. A small po tential is applied across the cathode and anode by a battery ; the current flow is measured by a galvanom eter. The sensing of ozone in the air sample is accomplished by the well known oxidation-reduction of po tassium iodide which is contained in
MDC 7 2 5 - 3 B Specifications Operating range Sensitivity Sampling rate Response time Power requirement Unattended operating time Dimensions and weights Ozone m e t e r Stript chart recorder Weatherproof case
INDUSTRIAL AND ENGINEERING CHEMISTRY
0 to 100 p.p.h.m./volume ± 2% of full scale About 140 c c . / m i n u t e 7 5 % of true value in 1 minute 110 volts a . c ; 100 w a t t s : one 1.34-volt H g cell Approximately 3 days 7 H X 6 Χ 11Η inches high, n e t weight 8Î4 l b s . 9 Χ ΖλΛ X 12 i n c h e s high, n e t weight 17M l b s . 12 X 6% X 1 4 ^ inches high, n e t weight 12M l b .
I/EC
& Materials the sensing solution. This reaction takes place on the cathode portion of the electrode support In this region, any ozone in the air sample reacts with the sensing solution as follows :
joes window shopping for you in the ever-increasing
market of Equipment, Materials,
New Products, and Services.
Manufacturers will be glad to supply additional
information.
Here's α Sampling of What You'll Find This Month For additional information on these and other items please turn the page
• Item No.
EQUIPMENT
0;i + 2KI + H 2 0 -* 0 2 + KOH + L,
Rugged heating wire for r u g g e d service comes as a three-component package
At the cathode, a thin layer of hy drogen gas is produced by a polar ization current:
New check valve comes with porcelain body, guided porcelain cone or alumina ball check, a n d a Teflon seat
3
High power plasma torch combines high thermal efficiency with negligible plasma contamination
4
P u m p i n g of liquids u n d e r high temperatures a n d pressures is possible with new steam-jacketed centrifugal p u m p s
5
Continuous mixer provides high quality mixes without sacrificing unnecessary operation time
7
Poly (vinyl chloride) ball valves are nontoxic, nonflammable, a n d almost completely nonaging
9
2e + 2H+ —H2 AVhen the voltage is applied to the electrodes (about 0.25 volt), the hydrogen layer builds to its maxi mum and the polarization current ceases to flow. When free iodine, I2, is produced by the reaction with ozone, it immediately reacts with the H 2 as follows: H 2 + l2 2HI Removal of hydrogen from the cathode causes a repolarization current of two electrons to flow in the external circuit, re-establishing equilibrium. Thus, for each ozone molecule reacting in the Sensor, two electrons flow through the external circuit. The rate of electron flow, or current, is directly proportional to mass per unit time of ozone en tering the sensor. The 725-3B requires very small amounts of contacting solution and air samples, and gives continuous, rather than intermittent readings, which are recorded on a 6-inch strip chart. The response time of the Sensor to a change of ozone concen tration in the air sample is quite rapid; about 75% of the new ozone value is recorded in one minute. The accuracy of the instrument has been carefully checked against other highly refined ozone measur ing techniques in the laboratory. Dept. IEC, Mast Development Co., Davenport, Iowa. 1 Prices quoted are those sub mitted by the manufacturer. They are subject to change with out notice. Prices are f .o.b. point of manufacture.
2
CHEMICALS AND MATERIALS New source of resins made from styrene a n d butadiene should give coating industry a big boost economically
16
Two new boron hydrides are available for experimental work
17
w-Sulfobenzoic acid is now on hand as an intermediate in a variety of applica tions
18
New silicone resin offers increased water repellency to masonry formulations at no increase in price
19
INSTRUMENTS Advanced process control digital computer system is based on latest available technology in the computer field
27
New liquid level indicator does not d e p e n d on capacitance or capacitors
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. . .
Miniature thermocouple with a sensing tip u p to four inches long is avail able
30
Magnetic alarm rotameter is designed to indicate high or low flows in a variety of ways
31
Integrated viscosity control monitor for controlling in-line viscosities is avail able
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Differences in refractive index of liquids as small as 0.0000007 unit can b e measured a n d recorded with recording differential refractometer
33
F i n d s o m e t h i n g i n t e r e s t i n g ? T h e n circle the number given with each item on the Readers' Information C a r d , page 103 A. And d o n ' t miss I / E C ' s selection of Manufacturers' Literature, page 98 A. VOL. 52, NO. 11 ·
NOVEMBER
1960
87 A
