54 CHEMISTRY AND HEAT 



recommended by the former. Also, the American Society of 

 Heating and Ventilating Engineers recommended the values 

 for the use of its members. The table gives the dimensions 

 of flanges, but not of fittings. Another series of values is the 

 Manufacturers' 1912 Schedule, which was adopted July 10, 

 lltli', to take effect Oct. 1, 1912. The latter schedule agrees 

 with the table on page 51, so far as standard flanges are con- 

 cerned, but has slightly different values for extra-heavy flanges 

 for pipes over 8 in. in diameter. 



CHEMISTRY AND HEAT 



CHEMISTRY 



Divisions of Matter. Matter is anything that occupies 

 space, and it exists in three states, namely, solid, liquid, and 

 gaseous. It is made up of molecules and atoms. A molecule 

 is the smallest portion of matter into which a body can be 

 divided and exist without changing its nature. An atom is 

 an indivisible portion of matter, or the smaller particle pro- 

 duced by dividing a molecule. A molecule is simply a group 

 of two or more atoms that are held together by their natural 

 attraction for one another. 



Elements and Compounds. Every body, or every portion 

 of matter, is either an element, a compound, or a mixture. 

 Iron, silver, sulphur, and oxygen are elements; wood, coal, 

 salt, and water are compounds; and atmospheric air is a mix- 

 ture. An element is a substance that cannot be divided or 

 broken up into other substances; thus, if a piece of silver is 

 divided and subdivided, each particle will still be silver. A 

 compound is a substance that can be divided into other sub- 

 stances; thus, if an electric current is passed through water, 

 the water is decomposed into two gases, hydrogen and oxygen. 

 A mixture is simply a combination of elements or compounds 

 in which each preserves its own nature; thus, air is a mix- 

 ture of oxygen and nitrogen and minute proportions of 

 other gases. 



