336 CHEMICAL DISCOVERY AND INVENTION 



1798, and in the earliest of his works he describes his " Re- 

 searches Chemical and Philosophical chiefly concerning Nitrous 

 Oxide and its Respiration " (1800). 



Ether has been known from the times of the alchemists and 

 from its being produced by the action of strong sulphuric acid 

 on alcohol, it was called in those days oleum vitrioli dulce. Its 

 use as an anaesthetic belongs exclusively to quite modern prac- 

 tice ; it is generally associated with chloroform. 



The other famous anaesthetic, chloroform, was discovered by 

 Liebig in 1832, but its remarkable physiological action was 

 recognised in 1847 by Sir James Young Simpson, who thus con- 

 ferred on suffering mankind for all future time a benefit of in- 

 calculable value. 



The alkaloids of opium and those of cinchona bark and many 

 other vegetable principles had also been introduced into regular 

 medical practice long ago. The characteristic of our own time 

 in respect to medicine arises from the great advances which have 

 been made in the knowledge of physiology and theoretical 

 chemistry, and recognition of the interdependence the one on 

 the other. 



A brief account of some of the more prominent among chemical 

 medicines now follows. 



Acetanilide, known as antifebrine, is produced by the action 

 of acetic acid on aniline, and is represented by the formula 

 C 6 H 5 NH.C 2 H 3 0. 



Acetyl Salicylic Acid, still known as aspirin, is the acetic 

 derivative of Salicylic Acid, which is itself orthohydroxy benzoic 



C 

 acid, C 6 H 4 <^-p.- This important compound exists in the 



meadowsweet and other plants, but is manufactured by heating 

 sodium phenate, C 6 H 5 ONa, in the presence of carbon dioxide, 

 as already explained. From the product dissolved in water sali- 

 cylic acid is precipitated by the addition of hydrochloric acid. 



Another acetyl compound is phenacetin, which is the para 

 acetamino derivative of phenetol C 6 H 5 .OC 2 H 5 . The formula 

 is therefore : 



Picric Acid is a pale yellow crystalline substance produced by 

 the action of nitric acid on phenol. It is trinitrophenol, C 6 H 2 



