INDUSTRIAL A N D ENGINEERING CHEMISTRY
686
The holder which supports the capillary device and the condenser are so arranged that no cold condensate can flow on the capillary. The lower end of the condenser is provided with a short flexible wire which touches the jacket and conducts all t h e c o n d e n s a t e smoothly to its walls, whence it flows back to the lower part without coming in contact with the capillary device. PROCEDlJRE-NUmerOUS measurements have been made with this apparatus, and it has been found to work well. The maximum pressure which we have employed is about 12 atmospheres (1751bs. per sq. in., absolute), which is within the safe operating pressure for Pyrex glass of this size. Precautions were taken, however, to protect the observer with a heavy metal screen, outside of which is placed heavy wire-plate glass. Strong solutions of alkali (about 85 grams of sodium carbonate Der liter or 5000 grains Figure 1-Ca illary Tube andI per gailon) attack the -glass €&der at high temperatures, resulting in a slight enlargement of the capillary bore. This is not serious and can be corrected by making calibrations from time to time with distilled water. These experiments cover solutions of sodium carbonate, sodium carbonate with a small addition of soap, and two samples of boiler water from commercial power plants. Sample A came from a boiler which had given priming trouble at higher concentrations but which was giving no trouble at the concentration represented by the sample. Sample B came from a boiler which was giving serious trouble from priming. Several determinations were made of the capillary rise for each liquid and the average values are given in Table I. The individual measurements never varied among themselves by more than 1 or 2 per cent. Table I-Capillary Rise --Temperature
SOLUTION Water Sodium carbonate 17.1 grams/liter (!OOO grains/gallon) Sodium carbonate 85.5 grams/liter (5000grains/gailon) So8 and soda, 17.1 mg. soap and IF10 mg. NarCOa per liter (1 grain soap and 100 grains NanCOS per gallon) Sample A Sample B
25'C. (77' F.) 5.99
110OC. (230' F.) Cm. 4.90
5.93
4.75
4.12
...
4.20
...
3.91
4.83 4.77
4.00 4.02
Cm.
5.90 5.79
183" C. (361' F.) Cm.
3.93
RESULTS-The table shows that there is no connection between surface tension and priming. Samples A and B were not analyzed as their composition is beside the present point. One sample did prime and one did not; both contained sodium salts a t considerable concentrations and both contained suspended matter. Their surface tensions a t the higher temperatures, as measured from capillary rise, are practically identical and they do not differ materially from the values for water or sodium carbonate solutions. Experiments w i t h Test Boiler
Results obtained in the laboratory had failed to establish any connection between surface tension and priming, since solutions which supposedly primed badly (as Sample B )
Vol. 17, No. 7
gave about the same capillary rise as distilled water. Further tests were made with a small test boiler built to scale, containing about 45 kg. (100 pounds) of water and operated a t about 5 atmospheres (75 pounds) pressure. Heavy glass peep holes were installed in each end of the boiler. At one time when the boiler was running smoothly a considerable quantity of soda ash was added and very serious priming resulted. Slugs of water were thrown bhrough the steam pipe and something more than half of the water was thrown from the boiler. Analysis of the residual water showed 10.26 grams of soda ash per liter (600 grains per gallon). The capillary rise for this water was 3.74 cm. a t 183' C. (361" F.) which value is slightly lower than that for pure water. Water was added to the boiler, followed by a quantity of tallow soap sufficient to give a concentration of 35 to 50 mg. per liter (2 or 3 grains per gallon). Serious priming occurred again with great slugs of water passing out through the dry pipe. On the following day, when the boiler was running quietly, 35 mg. of soap per liter (2 grains per gallon) were added. The water level rose higher than the top of the peep hole, but no slugs of water passed into the dry pipe. After the boiler was blown out, and when it was again running steadily, a large quantity of soda ash was added. This caused the water to rise above the level of the peep hole but did not cause priming into the dry pipe. Thus, both soda ash and soap caused s e r i o u s priming on one day and neither soda ash nor soap caused priming on the following day. Since soda ash does not change the surface t e n s i o n of w a t e r materially and soap does change it, it was concluded that there was no connection between priming and surface tension. The variable which governs priming was not d i s c o v e r e d in this work* Flguri 2-Apparatus for Determining some c h a n g e was Relation between Surface Tension and made in the operation Priming of the boiler, as regards this unknown variable, between-one day and the next; but this variable does not seem closely connected with surface tension.
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Salesmen's Courses The College of the City of New York has concluded a course of lectures, given under the auspices of the Salesmen's Association, for the purpose of interesting the salesmen of our industry in the scientific side of their activity. Fifty-six men, representing twenty firms in the chemical industry, enrolled in the course, which consisted of lectures with exhibits anci,experiments followed by lantern slides and motion pictures. Chemistry in Industry" was used as the textbook for the course. The average attendance at each of the lectures was an indication of the siiccess of the undertaking. What has been done a t the City College can be done in other industrial centers. Such assistance as we can give the salesmen represents a good investment of our time and effort.
