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URREY, TYPE TWO has ample power for rough roads and hills; has throttle (speed regulator) attached to steering wheel-one hand can manage both; automatic spark governor; cooling system that makes pumps and fans unnecessary; powerful brakes long wheel base; large wheels and tires; can opy top; water-proof side curtains; plate-glass swinging front; and other marked provisions for comfort, safety and reliability. $2000, complete with lamps, tools, etc. Other models $750, $850 $1350, $3000 THOMAS B. JEFFERY & COMPANY Main Office and Factory, Kenosha, Wisconsin Branches, Boston, Chicago, Philadelphia New York Agency, 134 West Thirty-eighth Street Representatives in all other leading cities.
Engineers, Architects, Draughtsmen-Students or Expertsshould get acquainted with the resources of supply for all drawing and sketching materials offered by this house.
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Answer: The voltage of a battery does not always indicate the state of charge. One method of finding the amount of charge in a storage battery is called the "Cadmium Test." The apparatus for making this test may consist of a small piece of cadmium, 5% inch by 5% inch by 1-32 inch, mounted so that a glass tube contains the conducting wire, wax being used to protect the soldered joint of copper and cadmium. With normal conditions of cell when fully charged and on open circuit, the difference of potential between the cadmium piece and the positive plate is approximately 2.5 volts, which is sufficient. The cadmium test is usually made at the center of the cell, giving uniform current distribution. The test will give readings, some of which are below 2.5 volts, if hydrometer test, temperature, and charge data show that the cell is not fully charged; but if the hydrometer, temperature, and other data show the charge to be complete, and the cadmium gives .I volt or more below 2.5 volts, the defective plate is determined by individual cadmium readings. When the battery is discharged—that is,
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Preparation for College
Instruction under the direction of the regular teachers in a resident engineering college.
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The full College Preparatory Course covers the entrance requirements of such a college as ARMOUR INSTITUTE OF TECHNOLOGY, and students satisfactorily completing this course are admitted to the college of engineering of that institution without further examination in the subjects taken.
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Hardening of Steel Tools
Question: Is it good practice to use acid baths for hardening steel tools? If not, what is a good formula?-E. S. K.
Answer: With acid baths, excellent results, so far as the hardened surface is concerned, can be obtained. Their use is not advocated, however, as the after effect is to rot the steel. A bath that gives excellent results is: Six quarts of soft water, one ounce of corrosive sublimate, and two handfuls of common table salt. Use when dissolved. Another formula for making tools tough and hard is: 1⁄2 teacupful salt, 1⁄2 ounce saltpeter, I teaspoonful pulverized alum, and I gallon Mention The Technical World, Feb. soft water. Mention The Technical World.
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CONSULTING DEPARTMENT-(Continued) to 1.8 volts-the voltage between the cadmium test piece and the positive plate should be about 2.05; and between the cadmium and the negative plate, .25. The cadmium should be positive to both elements. The voltage of the cell equals 2.05 .25 (= 1.8). If we have a cell in which the conditions tend to show full charge but the potential difference is low, a cadmium test is made. Whichever plate shows a falling off from the normal reading, that plate is the defective one.
The following precautions should be taken in making this test: It is advisable to have the cadmium plate wet before the test is made. The cadmium plate should be shaken occasionally to free it from any bubbles of gas that may form on the surface. The plate should be washed with water every time it is taken from the cell. The simplest way to accomplish this is to keep the cadmium tester in a beaker of distilled water. The cadmium should be free from impurities or foreign matter of any kind.
Armour Institute of Technology
CHICAGO, ILL., U. S. A.
The surface of the metal should not be scraped bright, but it should be allowed to oxidize slightly. There is a difference of potential between cadmium and cadmium oxide; and, as the bright surface oxidizes quickly, it would be practically impossible to keep the surface bright. Care should be taken that the cadmium does not come in contact with plates or connections. This may be prevented by covering the cadmium with rubber, and perforating the covering with numerous small holes.
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