INDUSTRIAL AND ENGINEERING CHEMISTRY
November, 1928
1239
Laboratory Humidity Cabinet' Irving C. Matthews and Alosco M. Burgess Easrarm K o m r COYPANY.ROCIIBSTSR. N. Y.
N air-conditioning cabinet, recently designed and built under the direction of these laboratories, possesses certain novel and uotewortby features of construction. This apparatus will give higher humidities than most similar equipment in general use, and teniperatures and humidities approaching tropical conditions are easily obtained. Description of Apparatus
A
Figure 1 shows a photograph of the apparatus assembled and installed. The cabinet itself is constructed of Alberene stone 1.5 inches thick, which has the advantage of resistance I
Received April 11. 1828.
Communicatioo 348 from K d a k Re-
to corrosion and also that of non-conductance of heat, hence requiring no further insulation for reasonable accuracy of control. All casings, ducts, and other parts exposed to moisture are of copper or brass. The operating parts are relatively simple, consisting essentially of fresh air intake, water or steam spray nozzle, series of eliminator plat,es or bafles, steam heating unit, and blower to circulate the moist air through the Alberene stone chambrr. The use of a thermostaticslly controlled steam coil as the heating unit has thus far proved satisfactory, and it is believed that this type of heater will give less trouble than the electrical heating units sometimes used in similar appara-
tus.
search Laboratories.
To obtain relatively high humidities, especially at higher temperatures, the steam injector is used. The w&ter spray nozzle bas proved quite satisfactory for low humidities. Temperature and humidity are controlled by diaphragm valves operated by a Foxboro recording and controlling instrument, which also records dry- and wet-bulb readings on a 24-hour chart, thus giving a permanent record of conditions for any giveii test. Construction details are sliown in Figure 2. The cabinet itself is 4 feet long by 2 feet Ginches wide by 2 feet 6 inches deep, outside dimeusions. Operation
Figure I-Humidity
Cabinet
B
To operate the apparatus it is simply necessary to open the steam valve to hester, open the wat.er or steam valve as desired for the spray, set the indicators on the recording instrument a t the desired wet- and dry-bulb temperatures, open the air-supply valve, and turn o u t h e m o t o r which o p e r a t e s t h e blower. Obviously, the water bottle which supplies the water box of the wet-bulb thermometer must be kept filled at all times when in use, the clock on the recording instrument should be wound, and the recording pens filled with
ink. Articles to be teated are either s u s p e n d e d 3-Shelf and Glass Rods where from glass rods s u p FigupeArticles Are Placed foc Tesfs ported in grooves near the top of the cabinet or placed on a glass shelf in the lower portion, as shown in Fibwre 3. This apparatus was built to replace a less satisfactory equipment of similar nature aiid is used in making accelerated weathering tests on metals and other malerials as well as for experimental purposes where conditions of high humidity a t various temperatures are required. The approximate cost of construction of the equipment as described, not including cost of installation, is ,51200. The cabinet is designed to maintain any desired temperature between 80" and 120° F. with humidity at any desired
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I N D USTRJAL AND ENGIiVEERING CHEiMIXTRY
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point from 80 to 100 per cent, provided, of course, that the normal humidity in the atmosphere does not exceed that required in the cabinet. Suggested Improvements After several months' experience with the apparatus described, the writers would suggest several improvements to increase its adaptability to laboratory use. The bottom of the cabinet could either be built at a slight angle with the horizontal or suitably grooved to permit
Vol. 20, No. 11
draining off into the drip pan of moisture deposited a t very high humidities. The cabinet could be constructed so that the top is inclined a t an angle of 15 to 20 degrees with the horizontal. This would allow moisture deposited a t high humidities to run down to the end instead of dripping on samples. In place of a single water spray nozzle a series of several nozzles would be preferable. The efficiency of water as a source of vapor supply would be very greatly increased if the air were passed through a veritable blanket of finely atomized water.
A Wing-Top Oxygen-Gas Burner' G . ROSSRobertson UNIVERSITY OF CALIFORNIA AT Los ANGBLES, CALIF.
HE recent adoption of pure natural gas in the local
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city servic-eto this laboratory has rendered glass-working with air-gas mixtures very difficult. Even operations with soft glass require an oxygen-gas blast. For the bending of Pyrex and even the medium sizes of soft glass tubing, an oxygen-gas burner with wing top has been devised as shown in Figure 1. The needle-valve mechanism was removed from each of two old Tirrill burners. These were of the common size which permits the cutting of a 3/J-inch S. A. E. standard male thread, as shown herewith. The v a l v e s w e r e fitted into a short length of 1-inch brass rod bored out and tapped with the S. A. E. thread to fit. A short section of one of the original burner tubes is fitted to the device, while below is provided a length of '/rinch brass rod as a sapport. On the lower end of the support was cut a standard ' / p inch pipe thread, which in turn was fitted with suitahle bushing t o a n o r d i n a r y plumber's galvanized-iron floor flange. A full current of natural Figure 1 gas is first run through one (Scale. fg in. = l i n . ) of the burner valves and lighted. Oxygen under pressure regulation is then cautiously introduced through the second valve, care being taken to have ample pressure-5 pounds or more-brick of the needle valve in order to minimize flurtuations. Enough oxygen is admitted to render the flame barely non-luminous. If an excess of oxygen is used, or the gas is turned off before the oxygen, an alarming though entirely harmless detonation occurs. The wing flame so produced is very effective in the bending of refractory tubing. With thin-walled tubing it is best to stopper one end, heat the tube until the proper section is constricted and the wall thickened, bend, and then blow out to the original diameter. It was somewhat surprising that an oxygen-gas mixture would not strike back regularly to the mixing chamber in a burner with such ample passageways. Prevention of such 1
Received June 8, 1928.
trouble seems to lie largely in the provision of an appreciahle quantity of paraffin hydrocarbons in the fuel used. The local gas, rated approximately as a 7: 2 (volume ratio) mixture of methane and ethane, and of 1150 B. t. u. value, shows a very slow rate of flame propagation. It is this sluggish action which renders ordinary Bunsen and blast flames so ineffective for the production of localized high temperatures where natural gas is employed. In the burner described herein, however. the relatively slow flame is turned to good account and permits reasonable control of what would otherwise be a highly explosive mixture. Usefulness on Other Fuels Experiments were carried out to test the usefulness of the burner on other fuels. Pure hydrogen was of course entirely unsuitable on account of rapidity of combustion. A synthetic water-gas mixture of equal volumes of carbon monoxide and hydrogen was also unsatisfactory. The trouble here is due, in part a t least, to the fact that the monoxidehydrogen flame is blue even without admixture of the oxidant, and the operator cannot estimate the proper quantity of pure oxygen to be added. The inclusion of as little as 15 per cent of natural gas improved matters greatly, not only affording flamecolor c o n t r o l , b u t also r e d u c i n g t h e tendency to s t r i k e back. Even g a s mixtures running as high as 75 per cent hydrogen were controllable p r o v i d e d the rest of the fuel was mostly natural gas and the pressure was adequate, as in normal city service. The burner ought to be satisfactory with Figure 2 m o s t coal o r oil gases, or even with well-carbureted water gas. Large-Size Wing Tops I n &w of the large capacity of the burner, one may use wing t,ops larger than the standard article of commerce. Figure 2 shows a simple assembly to serve the purpose. Two triangular pieces of *//sin.sheet brass, from 4 to 5 inches along
