Hygiene / by J. Lane Notter and R.H. Firth.

  • Notter, J. L. (James Lane), 1843-1923.
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: Hygiene / by J. Lane Notter and R.H. Firth. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    20/454 (page 4)
    the iodide of potassium. The potassium oxide produceo, causes an alkaline reaction, and turns the red paper to blue. Althougli small traces of ozone constitute a powerful agent for the purifi- cation of the air from waste organic matter, in larger quantities it acts as a violent irritant to the eyes and nose. Carbonic Acid.—Samples of air, no matter where collected, always _ contain another gas besides nitrogen and oxygen, called carbonic acid, and this usually to the extent of about 4 volumes in 10,000 of air. Carbonic acid is a clear colourless gas containing 12 parts by weight of carbon combined with 32 by weight of oxygen. It is produced when carbon, which forms the greater part of coal, is burnt. The carbon unites with oxygen, their union producing both light and heat with the giving off of carbonic acid gas. For this reason, it is the invariable product of the burning of animal and vegetable matter in the air, and is the choke-damp which collects in mines after an explosion. It is also largely given off by men and animals, as well as from the earth, more particularly in volcanic districts. Under the influence of sunlight, plants breathe in carbonic acid, retaining the carbon and setting free the oxygen. In the dark, this action of plant life is reversed, the oxygen being absorbed and carbonic acid given off. Carbonic acid, or as it is sometimes called, carbon dioxide, exists largely in Nature in combination, forming compounds called carbonates. It is readily obtained by adding dilute hydro- chloric acid to a form of calcic carbonate such as marble or limestpne contained in a flask and so arranged that the escaping gas can be collected into a suitable vessel. The acid acts upon the calcic carbonate, forming calcic chloride, water and carbonic dioxide; this latter escapes as a gas while the two former remain behind. Carbonic acid is faintly acid in taste and smell, and behaves in an exactly opposite manner to oxygen, inasmuch as it can neither support life nor combustion. It is a very heavy gas, being just 22 times heavier than hydrogen, which is the lightest of all gases. It is soluble in water, but the volume so dissolved depends largely upon temperature and pressure. The amount of carbonic acid present in the air varies according to place and season. Angus Smith found 0-36 parts per 1000 of air in London streets ; 0-4 in Manchester, while in country districts and on the tops of hills or mountains about 0-3 parts per 1000 of air has been the average amount found in the atmosphere. In inhabited rooms and stables, of course much larger quantities have been found. To the extent of 0*4 parts in 1000 of air carbonic acid is a normal constituent of our atmosphere, and unless it exceed that quantity it cannot be considered an impurity.