6 MATERIA MEDICA. 



nations of nitrous acid may be employed^ 

 either in a liquid or solid state ; they may 

 also be diluted with water, or mixed with 

 unctuous substances, to form detergent 

 ointments of any degree of strength that 

 may be required. 



Strong or concentrated nitrous acid is 

 of a deep yellow colour, approaching to 

 orange, and emits suffocating fumes of the 

 same colour. When water is added, the 

 yellow colour is destro3'ed, and it ceases to 

 emit fumes ; the same erFect may be pro^ 

 duced merely by the application of heat, in 

 this state it is termed iiitric acid. 



Aqua-fortis is made by mixing nitrous 

 acid with about an equal quantity of water. 



Muriatic Acid, or Spirit of Salt. This 

 acid is obtained by distilling common salt 

 with vitrolic acid. 



Spirit of salt is generally of a light yel- 

 low colour, and when exposed to the 

 air emits white suffocating fumes. This 

 acid is sometimes used as a caustic, to des- 

 troy excrescences or fungous flesh, or to 

 cleanse foul ulcers ; and being considerably 

 weaker than the two former, may bq applied 



