Fire and Heat 135 



the water in which it is dissolved? Compare soda water, or any of 

 the carbonated waters on the market. Water at ordinary temper- 

 ature is capable of absorbing practically its own volume of the gas. 



3. Is carbon dioxid heavier than air? Where, when unmixed 

 with water, would you expect to find the gas? Would mines and 

 deep wells be included in your list of places ? 



4. What test is used to determine the presence of carbon dioxid? 

 Is the substance produced from marble and hydrochloric acid the same 

 as that you collected from burning carbon in air or oxygen, or that 

 contained in air expired from the lungs? 



Carbon dioxid is more than half again as heavy as the air. That 

 is, if a unit volume, as a cubic yard, of air has a weight of 1, as one 

 gram or one ounce or one pound, an equal volume of carbon dioxid 

 has a weight of 1.5 grams, ounces, or pounds. 



Distribution and abundance. Carbon dioxid is universally 

 distributed in the air, in water in the soil, and in rocks, as well 

 as in all living things. In one kilogram of air carbon dioxid 

 weighs .5 gram. In a liter of air it makes up but .3 of a cubic 

 centimeter. Although it is half as heavy again as air, it is 

 generally kept well mixed by air currents, clouds, and rain- 

 fall. It forms about .01 per cent by weight of ocean water. 

 Many underground waters -are highly charged, as their efferves- 

 cence shows when they are released from earth pressure. The 

 effervescent waters of many springs are widely known, as those 

 of Saratoga Springs, New York. Carbon dioxid is especially 

 abundant in such rocks as limestone, marble, and chalk, which 

 because of this fact are known as carbonates, limestone and 

 marble being called calcium carbonates. For commercial pur- 

 poses carbon dioxid is prepared from limestone and marble 

 by heating or by treating with acids. By volcanic action great 

 amounts are returned to the atmosphere from the vast under- 

 ground stores. In the process of decay, all organic matter, 

 plant and animal, which contains a large proportion of carbon, 

 liberates quantities of the gas. This is largely absorbed by 

 water. In its union with water, carbon dioxid permeates the 

 crust of the earth, dissolving many substances which are carried 

 away by the water and redeposited elsewhere. Thus, together 



