CHEMISTRY 139 



a single firm produced in one year from coal tat a quantity of 

 indigo dye that would have required a quarter million acres 

 of indigo plant. 



The abundance and cheapness of newspapers and coarse wrap- 

 ping papers are due to the fact that man has learned to substi- 

 tute wood for rags in the manufacture of paper. Investigation 

 brought out the fact that wood contained the substance which 

 made rags valuable for paper making. Since the supply of rags 

 was far less than the demand, the problem of the extraction from 

 wood of the paper-forming substance was a vital one. After 

 repeated trials, it was found that caustic soda when heated with 

 wood chips destroyed everything in the wood except the desired 

 substance, cellulose; this could be removed, bleached, dried, 

 and pressed into paper. The substitution of wood for rags has 

 made possible the daily issue of many, large newspapers. When 

 we reflect that a paper of wide circulation consumes a ten-acre 

 wood lot per day, we see that all the rags in the world would 

 be inadequate to supply newspapers alone, to say nothing of 

 periodicals, books, tissue paper, and the like. 



Chemistry plays a part in every phase of life : in the arts, the 

 industries, the household, and in the body itself, where diges- 

 tion, excretion, etc., result from the action of the bodily fluids 

 upon food. The chemical substances of most interest to us are 

 those which affect us personally rather than industrially; for 

 example, soap, which cleanses our bodies, our clothing, our 

 household possessions; washing soda, which lighteus laundry 

 work ; lye, which clears out the drain pipe clogged with grease ; 

 benzine, which removes stains from clothing ; turpentine, which 

 rids us of paint spots left by careless workmen ; and hydrogen 

 peroxide, which disinfects wounds and sores. 



In order to understand the actions of these substances we 

 must study the properties of two groups of chemicals known 

 as acids and bases. The first of these may be represented by 



