RELATION TO ENVIRONMENT 



147 



infectants. Many of the chemical elements, such as chlorine, 

 bromine, iodine, and oxygen, are good disinfectants. The 

 heavy metals, such as gold, silver, and mercury, have quite 

 pronounced disinfecting value. Others, such as nickel, zinc, 

 and copper, have only a slight value; while others, as lead and 

 tin, have none. The acids and alkalies do not have a marked 

 germicidal value except when they are used in strong solutions, 

 and then they have a destructive action on metals and fabrics. 

 Mercuric chloride, or corrosive sublimate, is one of the most 

 effective of the inorganic salts. This has an antiseptic action 

 in a one-millionth solution, and a disinfectant action in water 

 in a one to five hundred-thousandth solution. This chemical 

 unites with protein matter, and its use as a practical disinfect- 

 ant is limited on that account. Certain of the silver salts 

 are used, particularly in medicine, as antiseptics. Lime is 

 of great value as a disinfectant, but when it is air slacked 

 possesses no value. A freshly prepared lime water solution, or 

 a whitewash, makes an excellent disinfectant, and is especially 

 valuable in disinfecting a stable or barn, because it has certain 

 properties in addition to its germicidal ones that are most 

 beneficial, such as absorption of odors, reflection of light, etc. 

 Chloride of lime is also an excellent disinfectant. It has re- 

 cently been shown to be very effective as a disinfectant of 

 sewage effluents. As a gaseous disinfectant sulphur has had 

 a very prominent place, and it is popularly believed that the 

 burning of a little sulphur in a room produces a good disin- 

 fectant. Sulphur has a good deal of value, but not nearly as 



