Manual of human physiology / by Leonard Hill.

  • Leonard Erskine Hill
Date:
1899
Catalogue details

Licence: Public Domain Mark

Credit: Manual of human physiology / by Leonard Hill. Source: Wellcome Collection.

    22/504 page 6
    of the glass. Float the measure-glass in a basin of water con- taining some broken ice. When the water in the glass has become cold, observe that its volume has decreased. Its weight you will find has not changed. 6. Make (i) a 6h per cent., (2) a ten per cent, solution of common salt and keep these by you in bottles. For (i) Weigh out 6\ grammes of salt and dissolve it in 1000 cubic centimetres of water. For (2) Weigh out 10 grammes of salt and dissolve it in 100 cubic centimetres of water. Density. An inch of cork is much lighter than an inch of lead. A pint of milk is heavier than a pint of water. The weight of one cubic centimetre of water is taken as the standard of density. The density of any liquid can be determined by weighing a measured volume of the liquid and comparing this weight with that of the same volume of water. A float will sink deeper in a light fluid than in one that is heavy. In comparing densities advantage is taken of this fact. Take a long wooden pen-holder and float it in the measure- glass full of water. Mark the level of the water on the stem. The float will sink less in urine or milk because the density of these fluids is greater than that of water. A glass instrument is sold called the hydrometer, which is made on this principle with the stem graduated. It is used to accurately determine the density of milk, bloody urine, &c., for density gives us indications as to whether the heavier substances in solution are dissolved in a greater or lesser amount of water. An accurate way of determining the density of a solid is to drop small fragments into glasses filled with a number of fluids of different and known density. If the fragment remain suspended, neither sinking nor floating in any one of the fluids, its density is the same as that fluid.
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