14 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



The acid is now prepared by more direct methods from 

 iron pyrites or from sulphur. The presence of sulphur in 

 pyrites l and in oil of vitriol was known in Boyle's time, but 

 the name SULPHURIC ACID by which the acid is now generally 

 known was not adopted until 1787. 



Aqua fortis or nitric acid. A second acid of mineral 

 origin was described by Geber as obtained by distilling a 

 mixture of saltpetre with green vitriol and alum. At a 

 later period Glauber showed that it could be prepared more 

 easily, and in a much purer condition, by distilling a mixture 

 of oil of vitriol and saltpetre from a glass retort heated gently 

 in a bath of hot sand over a furnace. From its remarkable 

 power of dissolving metals such as copper and silver, which 

 were not readily acted on by oil of vitriol, it came to be 

 known as AQUA FORTIS. In Boyle's time its acid properties, 

 its volatility, and its origin from nitre were indicated by the 

 name "acid spirit of nitre"; this was afterwards shortened 

 to nitrous or NITRIC ACID, the last name being introduced by 

 Lavoisier in 1787. 



Aqua regia By dissolving sal-ammoniac or salt in aqua 

 fortis, Geber prepared a still more powerful acid which was 

 capable of dissolving gold; it was therefore called AQUA 



REGIS, Or AQUA REGIA. 



Spirit of salt or muriatic acid. The method of prepar- 

 ing spirit of salt by heating salt with oil of vitriol in a 

 glass retort is due to Glauber. He had previously made it 

 by throwing a mixture of salt, green vitriol, and alum upon 

 the hot fuel of a charcoal fire and passing the fumes into a 

 large glass globe. The action of oil of vitriol on salt produces 

 a pungent fume which escapes into the air and is lost ; but 

 Glauber found that this fume condensed readily in a receiver 

 half filled with water, giving an acid liquid which he described 



1 "Vitriols are produced from the stone . . . called Marchasite, and 

 from it on the application of fire the flowers of common sulphur are 

 elicited in considerable abundance " (John Mayow, Medico-physical 

 Works, 1674 ; Alembic Club Reprints, XVII. 28). 



