Elements of physics for medical students / by Frederic James M. Page.

  • Page, Frederic James M.
Date:
1907
Catalogue details

Licence: In copyright

Credit: Elements of physics for medical students / by Frederic James M. Page. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

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    in the upper pan until the mark d is level with the surface of the water—say 35*1 grams are required ; a penny is placed in the pan, and weights are again added as before (25'65 grams). So the weight of the penny in air is 35-1 — 25-65 = 9*45 grams. The penny is then placed in the pan c under water, and weights are added till the mark is again level with the surface of the water; this requires 20'70 grams. So the penny in water weighs 35'1 - 20'7 = 8'4 grams, and its loss when weighed in water 9 45 is 9-45 — 8-4 and its sp. er. = —-rv = 9. ^ ° 1•05 The common hydrometer consists of a hollow glass or brass vessel weighted at the bottom and furnished at the top with a long graduated stem (Fig. 21), the weight in the lower bulb (mercury or shot) being so adjusted that the instrument floats at the required level. The reading on the scale at the surface of the liquid gives the sp. gr. It is usual to have several of these hydrometers ; thus, one would read from 1U00 to 1050, another from -950 to 1-000, and so on; by this means a stem of inconvenient length is avoided. Hydro- meters are called Urinometers, Lactometers, Alcoholo- meters, etc., according to the liquid for which they are specially suited. The graduation of a hydro- meter should be verified by the sp. gr. bottle and the balance, if any important conclusions depend on the readings. The temperature of the liquid should always be 15-5° C. This is particularly important in the case of urine.