The chemistry of plant and animal life . water than is occurrence of nitrogen and oxygen in the air, andthe chemical and physical properties of these gases havebeen discussed in Chapters IV and V. 68. Carbon Dioxid.—The amount of carbon dioxid inthe air is small, about per cent., and it is supposedto remain fairly constant in amount. It is producedfrom : (i) combustion of carbon-containing materials, asfuels ; (2) decaying of organic matter ; and (3) respira-tion of animals. The carbon dioxid of the air serves asfood for plants and is used for the construction of planttissue.
The chemistry of plant and animal life . water than is occurrence of nitrogen and oxygen in the air, andthe chemical and physical properties of these gases havebeen discussed in Chapters IV and V. 68. Carbon Dioxid.—The amount of carbon dioxid inthe air is small, about per cent., and it is supposedto remain fairly constant in amount. It is producedfrom : (i) combustion of carbon-containing materials, asfuels ; (2) decaying of organic matter ; and (3) respira-tion of animals. The carbon dioxid of the air serves asfood for plants and is used for the construction of planttissue. The amount produced and that used by vegeta- AIR 67 tion nearly balance each other, so that the carbon dioxidin the air remains fairly constant. While the percentageamount in the air i3 small, the total amount is quitelarge ; it is estimated that over each acre of the earthssurface, there are about 30 tons of carbon dioxid at thedisposal of plant bodies. Carbon dioxid itself is notsuch a poisonous gas, but it is usually associated in. Fig. 36.—Ventilating board in window for obtaining fresh air. respired air with noxious and poisonous products thrownoff by the lungs. Hence the amount in a room is takenas the index of the completeness of ventilation. When-ever the carbon dioxid in a room exceeds percent., the poisonous products associated with it are 68 CHEMISTRY considered to be too large in amount for perfect sanitaryconditions. While carbon dioxid is a product of respira-tion, and is of no direct economic importance to animals,it is indirectly of great importance because of its servingas food for plant bodies. It is a heavy gas, but in a roomit diffuses and is quite evenly distributed. Its presencein pure and in respired air can be shown by the followingexperiment: Experiment g.—Pour lo cc. of lime water (calcium hydrate)into a test-tube, and blow through it, using for the purpose a cleanglass tube. Observe the precipitate of calcium carbonate. Expose
Size: 1524px × 1639px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyorklondonthema
