164 Introduction to the Study of Science 



in tanks, or combined with water to form ammonia water 

 (ammonium hydroxid). Ammonia water is highly concen- 

 trated, many times stronger than that sold for household use, 

 and is employed generally for cleaning purposes, such as re- 

 moving certain kinds of stains and grease spots from articles. 

 The ammonium sulfate is one of the most valuable fertilizers, 

 furnishing a large amount of nitrogen in a form directly avail- 

 able for plants. Ammonia gas is widely used in refrigeration 

 (page 151 ff.), and in the preparation of carbonate of soda (cf. 

 the Solway Process in any book on industrial chemistry). 



Coal-tar. Coal-tar is the substance with which many of 

 the modern miracles of constructive chemistry have been per- 

 formed ; it is a veritable treasure-trove as treated by the skill- 

 ful chemist. Under proper treatment coal-tar yields a num- 

 ber of substances called hydrocarbons, which form the basis 

 for many kinds of products contributing to the health, beauty, 

 wealth, and destruction of life. The principal hydrocarbons 

 derived from it are benzene, naphthalene, anthracene, toluene, 

 and phenol, commonly known as carbolic acid. 



From these basic substances many valuable products are 

 derived. Phenol is converted by the action of concentrated 

 nitric acid into picric acid used in explosives. Other products 

 from these basic substances are aniline and many dyes derived 

 from it ; alizarin, purpurin, and many other dyes from these ; 

 drugs such as phenacetin, acetanilid, salycilic acid, antipyrin, 

 sulfonol, and many anaesthetics and disinfectants ; some of 

 the finest perfumes ; flavoring essences, as lemon, vanilla, bitter 

 almonds, etc. ; saccharin, which is five hundred times sweeter 

 than cane sugar but of no food value ; art materials, such as 

 printing inks, photographic developers, varnishes, etc. Indeed 

 the old jingle is apt : t y 



" There's hardly a thing that a man can name 

 Of use or beauty in life's small game, 

 But you can extract in alembic or jar 

 From the ' physical basis ' of black coal-tar 



