LESSONS IN CHEMISTRY. 143 



on the easy ignition of phosphorus by friction, when mixed with 

 oxidizing agents, like chlorate of potash, the glue only servingto 

 bind the other parts together and attach them to the wood. The 

 phosphorus ignited by friction sets fire to the sulphur or paraf- 

 fine, which in turn ignites the wood. Several different " match 

 compounds" are made. When chlorate of potash is used there 

 is a slight explosion when the match is lighted. When potassium 

 nitrate is used a silent match is made. This form is most com- 

 mon in Germany, while the other is more common in this country 

 and in England. 



A single match is a little thing, but the manufacture of matches 

 for the use of mankind is one of the great industries of the world. 

 More than 2,000 tons of phosphorus are used annually with cor- 

 responding amounts of the other ingredients, and thousands of 

 acres of forests are necessary to supply the splints used every year. 

 It is estimated that forty thousand millions of matches are used 

 annually in the United States alone. Matches made with red 

 phosphorus, called safety matches, are sometimes manufactured, 

 but for some reason they are not in general use. A match is 

 made in France, using red phosphorus, which is ignited by break- 

 ing the match and rubbing the ends together. In Mexico matches, 

 as generally made, are little wax tapers, tipped at both ends 

 with the " match compound." 



Phosphorus forms several compounds with oxygen and hy- 

 drogen. When phosphorus burns in air or oxygen, the dense 

 white fumes formed are phosphoric oxide. This oxide com- 

 bines with water forming two acids as P 2 5 -j-H 2 0=H 3 P0 4 meta- 

 phosphoric acid and P 2 5 -h3H 2 0=2H 3 P0 4 orthophosphoric acid 

 commonly called phosphoric acid. It is the most important of 

 the compounds of phosphorus. It is tribasic, forming three 

 salts with the same metal, but the most common and important 

 salt is calcium phosphate, the chief mineral constituent of the 

 bones, and the form in which phosphorus usually occurs in 

 nature. 



Phosphorus (P) is an indispensable ingredient in the food of 

 animals and plants. No other mineral substances can bear com- 



