I N D U S T R I A L A N D ENGINEERING CHEMISTRY
April 15, 1929
109
Containers for Caustic Solutions' Byron A. Soule UNIVERSITYOF MICHIGAN,ANN ARBOR,MICA.
AUSTIC soda stored in an unprotected glass bottle attacks the glass. The liquid, becoming saturated with silicate, soon is unsatisfactory for use, especially in analytical work. Various expedients have been suggested to eliminate this difficulty. Among them may be mentioned the following: (1) Coating the inside of the container with paraffin or ceresin. While either is easily applied, both are open to the objection that, unless in a relatively thick layer, they soon separate from the glass and float to the surface of the liquid, thus leaving the bottle unprotected. (2) Painting the bottle with Bakelite varnish. This is attacked by caustic solutions and soon separates from the glass in large flakes. Difference in coefficient of expansion between the glass and varnish may also be responsible for the flaking. (3) Use of containers made from hard rubber. These, while effective, are opaque and somewhat costly. (4) Use of ceresin bottles. These are obtainable only in smaller sizes and tend to soften during hot weather. Since all of these devices are open to objection, i t was decided to try various others. After some exploratory tests, rubber paint2was found to be unaffected by sodium hydroxide solutions, at least up to a concentration of about 5 normal, which is the highest ordinarily encountered in a laboratory. On March 1 five bottles were coated with rubber paint as indicated in Table I. Table I-Coats SOLUTION 1 2 3 4
-- 5
of P a i n t a n d S t r e n g t h of Alkali Solutions NUMBER OF COATS NaOH NORMALITY 1 3 5 0.1 3
1 Received
November 17, 1928. 2 Thermoprene, Acid Seal Paint No. 1023, obtained from The B. F. Goodrich Co., Akron, Ohio. See Gray, IND. END.CHEM.,20, 156 (1928).
Th% next day the first three bottles were filled slightly over half full with sodium hydroxide solutions of the concentrations specified (Table I) and then placed in a dark cupboard. On March 7 the last two bottles were filled and placed beside the others. When next examined, on March 14, all samples seemed to be in good condition except No. 3, which apparently had lost some of its coating above the surface of the liquid. On May 12, no notable change having occurred, the bottles were transferred to the top of a laboratory desk and exposed to bright daylight, but not direct sunlight. They stood thus all summer. On October 6, approximately 7 months after the experiment was started, every sample was free from sediment. The paint in No. 5, beneath the surface of the liquid, was slightly lighter in color. No other difference was observed. A portion of the 5 normal solution was removed and acidified to test for silicate. After standing more than 1 hour a slight cloudiness was noted. Examination of the bottle where the coating was apparently gone revealed a thin, tightly adherent film of rubber, evidently of adequate protective thickness. Standardization of solution 4 a t various times during the test period has given a practically constant value for the normality (Table 11). Table 11-Standardization DATE April 9 May 12 October 6
of Solution 4 NORMALITY 0.0876 0,0873 0.0873
Note-The use of rubber paint for protection of glass bottles against the action of hydrofluoric acid has proved unsatisfactory. Gaseous hydrogen fluoride passes through the coating fairly readily and attacks the glass. This ultimately results in a separation of the rubber from the glass.
A Continuous Still for Conductivity Water' C. C. DeWitt a n d Geo. Granger Brown DEPARTMENT OF CHEMICAL ENDINEEPING, UNIVERSITY OF MICHIGAN,ANN ARBOR.MICH.
A,
CONTINUOUS, practically automatic fractionating column for producing very pure, or conductivity, water has been constructed which has proved so satisfactory that other laboratories may be interested in its construction. Construction The equipment consists essentially of two block-tin bodies, 1 and 6, equipped with block-tin coils and connected to the bottom of two columns, 4 and 2, interconnected a t the top, and two condensers, 3 and 5, one at the top of each column. All parts of the still coming in contact with water or vapor are made of block tin. The still body containers are made of two 8-inch wroughtiron pipe nipples 18 inches long, provided a t each end with an 8-inch flange screwed flush with the nipple end, as indicated by the heavy lines in the figure. The block-tin lining for t h e still is prepared by rolling a sheet of block tin 24l/1 by 1
Received November 26, 1928.
18l/2 inches to form a cylinder 24l/a inches high. The edges are butted and burned together both inside and out with a hydrogen-air torch flame. An annular flat ring of block tin 111/2 inches outside diameter by 77/8 inside is burned on one end of each cylinder to form a block-tin flange. The cylinders are then placed flanged ends down on a flat support and the 8-inch pipe nipples and flanges slipped over the tin stills. The block-tin cylinders are located centrally within the nipples and the space between the cylinders and the nipples is packed with insulating material lightly tamped into place. Similar tin rings of the same dimensions are slipped over the top of the tin still bodies, pressed against the flat faces of the nipple flanges, the projecting rim of the cylinders peened over the edge of the flat annular tin rings, and the joints welded with the torch. The block tin used in building these stills is l/10 inch thick. The bottoms of the still are made integral with the steam coils as indicated in the figure. The steam coils are made by winding 24 feet of block-tin pipe, 11/16 inch outside diameter
