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protective coating compositions in seeking a control and a knowledge of the cause of livering difficulties. Literature Cited (1) Bishop, Kittredge, and Hildebrand, J . Am. Chem. Soc., 44, 135 (1922). (2) Dieterich, 6cAnalysisof Resins, Balsams, and Gum-Resins,,, Scott, Greenwood, and Son, 1920.
(3) Gardner, Paint Mfrs. Assocn. U. S., Tech. Circ. 844, 16 (1929). (4) Harries and Nagel. _ . Ber.. 55B. 3822 11922): , . . Wiss. Verafentlich. Siemens-Koneern, 8, 12 (1924). ’
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(5) Kolthoff and Furman, “Potentiometric Titrations,” p. 30, John Wiley and Sons, 1926. (6) Marling, Paint Mfrs. Assocn. U. S., Tech. Circ. 819, 535 (1927). (7) McBurney and Nollau, Canadian Patents 284,963 and 284,964 (November 20, 1928). (8) Nagel and Korchen, Wiss. VevlifentZentlich. Siemens-Konzwn, 6, 235 (1927). (9) Popoff, Kunz, and Snow, J. Phys. Chem., 82, 1055 (1928). (10) Popoff and M c H e n v , IND. ENQ.CHEM.,40, 534 (1928). (11) Seltz and McKinney, Ibid., 20, 542 (1928).
A Combination Electrochemical Switchboard‘ W. Faitoute Munn 318 WHITE ST., ORANGE, N.
J.
NEW compact electrochemical switchboard has been laboratory supply house, but the low resistance is more diffidesigned which is very useful in a number of fields of cult to obtain, so the writer made one by winding on a 1work. It may be used for the deposition of metals, inch (2.5-cm.) diameter cardboard tube thirty turns of No. either for the plating or deposition of one metal or for the 18 pure nickel wire, alternating with string of such diameseparation of two or more elements by means of voltage con- ter that it would well support the separation of wire and a t trol. It may be used for pyrometry measurements by em- the same time not so great as to extend above the outer level ploying the millivolt connections and standardizing the of the wire. This is necessary to allow a perfect contact of thermocouple used against a known seriesof temperatures and the sliding spring which is finally mounted above the coil. drawing a graph to be used for all future readings. It may be These two resistances are connected in series, the rough apused for low-voltage testing of primary batteries, ampere proximation of the voltage and amperage desired being obreadings, either on plating baths or on outside separate cir- tained by changing or moving the slide on the high resistance cuits, or for millivolt readings. This apparatus has been and the final accurate adjustment being made by the slide on thoroughly tested, has been in use for a number of years, the low resistance. A double-pole, double-throw switch is mounted on the and can be relied upon to give very satisfactory results. The apparatus is mounted on a piece of ‘/*-inch (1.3-cm.) board and contact buttons (lower right-hand corner) are slate, 2 feet (60 cm.) square. There are two meters-an am- connected with a number of Edison-Lelande batteries or meter having a full-scale deflection of 10 amperes and a milli- dry cells. The buttons should be placed far enough apart volt meter having a full-scale deflection of 75 millivolts. so that the switch contact blade does not touch any two conThe millivolt meter is wired for voltmeter use by connecting secutive buttons when being moved around the arc. The in series with the millivolt terminal connections a coil of No. number of buttons and also the number of cells used will de40 Tarnac, double silk-insulated wire or other low-tempera- pend upon the voltage required by the user of the apparatus. ture-coefficient alloy wire, the amount being found by- experiment and checked by comparing with an accurate standard voltmeter so that the fullscale deflection will give a reading of 7.5 volts. This reading takes the place of the 75-millivolt )+ reading. This resistance is shown in the drawing , m “V.R.” A milliampere reading on the same M meter is obtained by making up a small shunt resistance. (“M.A.Shunt” in the drawing) and corrected by checking against a standard milliammeter so that the full-scale deflection will read 750 milliamperes. These calibrations should first be only roughly approximated and wired and mounted according to the drawing and finally corrected after all the wiring has been completed. This precaution is very necessary as the wires used in connecting up the board give sufficient resistance to affecb the calibration of the meters very appreciably if such calibration took place before the connections on the board were made. All wiring should be done with heavy copper inI I sulated wire, nothing smaller than No. 14 B. & s. being used, and all joints and connections should be carefully soldered, using resin, and not zinc salts or other compounds, for the flux. There are two resistances-a high resistance, about 100 ohms, and a low resistance. The high-resistance unit may be purchased at a
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INDUXTRIAL A N D ENGINEERING CHEMISTRY
If everything is now completed and the deposition of copper, for example, is required, the platinum cathode and anode which are suspended in the solution to be electrolyzed are connected to the minus and plus terminals, respectively, shown in the lower left-hand corner of the board. The double-pole switch is now thrown to the right, thus showing a volt reading across the bath terminals or electrodes, same being indicated on the left-hand meter. The current will be registered on the right-hand meter. If the ampere reading is less than 0.5 its accuracy will be doubtful, so to obtain an exact ampere reading the double-pole switch is thrown to the left, whereby the left-hand meter will register the fraction of an ampere in milliamperes. The bath may then be adjusted as t o current flow desired by moving either, or both, of the variable resistances. The voltage across the bath may now be found at any time by simply throwing the switch handle to
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the right. If the voltage is not correct, it may be changed by cutting in, or out, the number of cells on hand, by means of the switch and buttons on the lower right corner of t,he board. Outside volt readings on any low-voltage circuit may be obtained on t.he left meter by connecting the battery in question to the two upper left-hand terminals and throwing the handle of the double pole switch to the right. Outside ampere readings on any circuit may be obtained on the right meter by connecting the battery circuit in series with the two upper right-hand terminals. Outside millivolt readings or pyrometer readings may be obtained on the left meter by connecting the thermocouple to the two upper, central terminals. As soon as the worker is acquainted with the design of the apparatus described above, he will find it very useful and' rapid, and it will save more time, labor, and equipment in a short time than the entire cost of construction involves.
Corrosion Testing Apparatus' D. F. Othmer EASTMAN KODAK Co., ROCHESTER, N. Y.
HIS apparatus was devised for the testing of the rate of corrosion of various volatile liquids on a large number of samples of various metals. It was desired to test the materials with boiling acids of various concentrations and with various volatile impurities. It was necessary to find a material with a minimum rate of corrosion throughout a wide range of concentration. The apparatus consists of a balloon flask heated electrically to boil the liquid and supply vapors to a glass column packed with beads or small glass Raschig rings2 supported by a glass bulb pierced with holes and resting on indentations in the neck of the column as shown. A condenser with calcium chloride tube is superimposed as shown. The lower end of the column is drawn to a tip and has two small holes blown in the side just above this neck. Vapors enter these lateral openings and liquid runs down the tube wall and is discharged through the tip without priming. The lower end of the condenser is finished in the same way. The pieces of metal to be tested are inserted at various heights and are continually in contact with the vapors ascending and the hot clean wash descending the column. If a pure substance or an azeotropic mixture, such as nitric or hydrochloric acid and water, is boiled in the flask, the concentration of liquid throughout the column will be constant and samples a t different heights will have the same wash. If a mixture of other than constant boiling point is boiled in the flask, the concentrations of wash at different heights will vary, but in different columns of the same length they will be the same at the same height. These concentrations may be measured by sampling a t liquid outlet tubes at various heights (not shown on the drawing), but when only a comparative ratio between rates of corrosion on different metals is desired, this is not necessary and the samples are merely inserted at the same heights. Two of these columns of the same dimensions were set up above boiling dilute hydrochloric acid of 16.25 per cent HC1. Identical samples of sheet nickel were inserted in each of the columns 25 cm. and 125 cm. from the bottom of the packing. The columns were packed to a height of 50 cm. above the top of the upper sample and surmounted with condensers. A
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Received April 12, 1929. Available in various sizes from the Technical Glass Co., Rochester,
wash of about 30 cc. a minute was obtained in each column The test was run for 18 hours, at the end of which time the samples at the bottom were found to have lost 0.92 and 1.09 per cent, respectively, while those in the middle lost 0.011 and 0.007 per cent, respectively. No analysis was made of the acid strength in the column, but these data and the vapor composition curve of hydrochloric acid and w a t e r (1) indicate considerable difference in the acid strength at the two heights. T h e a d v a n t a g e s of t h i s method of determining the rate of solution are several: (1) The pieces to be tested a r e i n contact with saturated vapor and boiling liquid a t all times. (2) Metallic salts settle in the pot, and the wash liquid is always clean and uncontaminated with the accumulations of the products of corrosion (as it would usually be in plant apparatus). (3) Because of these advantages, the rate of corrosion may be studied under more nearly reproducible c o n d i t i o n s , a n d comparative tests on d i f f e r e n t materials have a greater value in determining relative usefulness.
Literature Cited (1) Othmer,IND, ENG.CHEM.,20, 743 (1928).
Mexican Textile Industry Showing Improvement The depression in the Mexican textile industry, which prevailed throughout 1928, showed no signs of abatement during the first six months of 1929, but since that time the position of the industry has improved considerably, according to information received in the Textile Division, Department of Commerce.
