State board questions and answers / by R. Max Goepp.

  • Goepp, R. Max (Rudolph Max), 1866-1950
Date:
1911
Catalogue details

Licence: Public Domain Mark

Credit: State board questions and answers / by R. Max Goepp. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    Define specific gravity. Give a method of determining the specific gravity of a solid substance insoluble in, and heavier than water. Specific gravity is the relative weight of equal volumes of different sub- stances, one being used as a standard. Find the weight of the substance in air and then in water (under standard conditions), and divide its weight in air by its loss of weight in water; the quotient will be the specific gravity. Example: Weight of iron in air =115.56 gr. Weight of iron in water = 100.08 gr. Loss of weight in water = 15.48 gr. = the weight of the volume of water displaced, hence— 115.56-^-15.48=7.46=^6 specific gravity of iron. What is the unit of comparison in determining the specific gravity of (a) solids and liquids; (b) of gases? (a) Pure water at 40 C. and a barometric pressure of 760 millimeters, according to the French system; or 620 F. and 30 inches barometric pres- sure, according to the English system. The specific gravity of solids and liquids is usually taken at a temperature of 15.50 C. (6o° F.). (b) Air or hydrogen at o° C. and 760 millimeters, according to the French system; or 6o° F. and 30 inches pressure, according to the English system. Describe (a) a hydrometer, (b) a pyknometer. Name some varieties of hydrometers. (a) A hydrometer (densimeter) is an instrument employed for deter- mining the specific gravity (density) of liquids. It consists of a graduated glass tube, with one or two bulbs at the lower end loaded with mercury or shot. (b) A pyknometer is a glass specific gravity bottle having a thermometer and a very narrow or capillary tube. Varieties: alcoholometer, lactometer, urinometer. Describe a urinometer and give the precautions to be ob= served in its use. A urinometer is a hydrometer with a scale usually ranging between 1000 and 1060, used for determining the specific gravity of urine. The urine to be examined must be kept at 15.50 C. (6o° F.); the urinometer freed from all adherent bubbles of air and not allowed to touch the sides of the jar. The specific gravity is then read off on the scale, reading from the base of the meniscus where the stem cuts the surface of the liquid. A correction must be made for any variation of temperature. For an increase of each 30 C. above 15.50 C. the specific gravity must be increased one degree, and for a decrease of each 30 C. it must be lowered one degree. How would you determine the specific gravity of a liquid? By placing a hydrometer in the liquid (under standard conditions) and noting the depth to which it sinks by the markings on the stem. The
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