A Gas-Tight Stirrer'


the bearing with the use of fine emery. The construction of the stuffing box is fully explained in the diagram. The packing used may be cotton waste s...
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I N D U S T R I A L A N D ENGINEERING CHEMIXTRY

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the end of the selected interval the residual gas was drawn through the absorbing solution and analyzed. Control analyses were made on the apparatus to determine the actual amount of gas being put into the bulb. The results are shown in Fig. 6.

Vol. 15, No. 11

chloropicrin, and mustard gas-are all highly soluble. I n fact, practically all the gases suggested for war use that are at all suitable for the purpose are sufficiently soluble in rubber t o make the protective effect of the face-piece material well worthy of consideration. Aside from its relation to war gas problems, the physiological method of gas determination herein described should be of assistance in determining the extent and rate of absorption of many vapors. Data of this kind should be valuable in the study of problems of sanitation, ventilation, hygiene, and occupational diseases. ACKNOWLEDGMENT The writer wishes to extend his sincere thanks to R. G. Pierre for his cooperation and suggestions, and to Stanley K. Reimarrn and Rolland R. Etter for their active assistance.

A Gas-Tight Stirrer' By George E. Holm and George R. Greenbank B U R E A U OF

FIO. 6-ABSORPTION OR CELOROPICRIN B Y AKRONTISSOTFACE-PIECE MATERIALS.TIMEOA EXPOSURE-18 HOURS

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It will be noted that the absorption curves cross a t 3 hours' exposure. This indicates that the chloropicrin is absorbed a t a faster rate than phosgene, but is also given up at a faster rate when fresh air is drawn into the bulb. When a chloropicrin-containing test piece was dropped into a 500-cc. bottle of fresh air, within 5 minutes the air in the bottle caused the eye to close in less than 4 seconds, indicating that the chloropicrin is given up quite rapidly when the equilibrium is disturbed. The same is not true, however, of phosgene, and it is probable that there is a chemical combination between the rubber and this gas. With chloropicrin the phenomenon is an apparently simple solution. DISCUSSION OF RESULTS A study of this series of experiments cannot fail to lead to the conclusion that rubber and rubberized cloth are very efficient in removing small quantities of war gases from air. It also seems clear that the rate of absorption is rapid enough to account for the fact that men are not gassed in the Tissot type masks even when these masks allow several hundred cubic centimeters of gas-laden air per minute to leak in. I n the case of a gas that is not soluble in rubber the protective effect of the face piece would not be in evidence. It happens, however, that the three really important gases-phosgene, I

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CONCENTRATION OF PHOSG€NE 900 PPM -INITIAL CONCENTRATION Of CHLQRPICRIN 650 PPM -INITIAL

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CURVE I- CHLORPICRIN CURVE ~-t'HOSG€NNE

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ABSORPTIVEPOWER AND PHOSGENU

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ANIMALINDUSTRY, WASHINGTON, D. C.

T H E accompanying cut illustrates the principal features of the stirrer. The bearing and the shaft are machined from steel and hardened, and the shaft is then lapped to fit the bearing with the use of fine emery. The construction of the stuffing box is fully explained in the diagram. The packing used may be cotton waste saturated with the same oil as that used for lubrication. Brass inlet and outlet tubes of l/l&ch diameter are soldered into grooves made in the bearing. Although the apparatus may be constructed in -dimeniions suitaile to the work in which it is to be used, the size found most suitable in laboratory work was of the following d i m e n s i o n s : $:' length of bearing, 2l/4 inches; diameter of bearing, 6/8 inch; length of shaft, 7 inches; diameter of shaft, l / 4 inch; diameter of stuffing box, 3/8 inch. The glass stirrer is fastened to the shaft with litharge-glycerol cement. It is closed to prevent contact of the liquid with the metal shaft, and contains a small hole, A , just above the level of the liquid. Upon rapid stirring, the gas above the liquid is drawn through this hole and the liquid is drawn in through the Iower end of the stirrer. Both are thrown out through the arms of the stirrer, thus producing a continuous circulation and mixing of the liquid and the gas in the vessel under a constant gas pressure. The apparatus shown has been used where thorough mixing of a gas and liquid was desired and where it was desired to measure the quantities of gas absorbed by a liquid in successive intervals of time. The stirrer may be run at a high speed for a long time without great wear, and will also permit relatively high vacuum or pressure within the vessel, without danger of gas leakage. OC*"