CHEMICAL DISINFECTANTS 137 



protecting envelope about the bodies of the bacteria, being there- 

 fore unreliable for disinfecting sputum and pus. It is also more 

 useful and powerful when it is acidulated with a 5. percent of 

 HC1, or when it is mixed with common salt or ammonium chloride. 

 In culture 1^1,000,000 solution prevents the growth of most 

 pathogenic bacteria. Biniodide of mercury is said by some ob- 

 servers to be more powerful than the bichloride. It is certainly 

 less likely to be interfered with by albumins. 



Sulphate of copper in water is a powerful germicide. It is more 

 potent in watery solution than in bouillon. It has a remarkable 

 affinity for algae and for moulds. The author found that if 

 moulds are put into alkaline solution of copper sulphate and 

 heated, the copper enters into chemical union with the protoplasm 

 of the mycelia, hyphae, and the spores; 1-400,000 of copper sul- 

 phate in water destroys the typhoid bacilli. Even nascent copper 

 kills the typhoid bacilli, so that copper foil in drinking water has 

 the power, after a few hours' contact, of destroying bacteria in 

 the water. 



The silver salts are useful in medicine as disinfectants, especially 

 on mucous surfaces. The nitrate of silver is one of the most valu- 

 able of all preparations; it is about a fourth as efficient as 

 bichloride of mercury and is not nearly so toxic. Some of the 

 albuminates of silver are useful because of their non-irritating 

 action. 



Acids, especially the mineral ones, are valuable disinfectants in 

 not too dilute solutions. They act chiefly as inhibitors of growth 

 rather than destroyers of bacterial cells. In the healthy stomach, 

 hydrochloric acid acts as a normal disinfectant, and in disease, 

 where it is absent, it must be added in order to prevent decom- 

 position of food. Boric acid is useful in medicine on mucous 

 membranes. 



The halogens, iodine, bromine and chlorine, are active agents 

 for the destruction of bacteria. The cheapest of these is chlorine. 

 It acts best in contact with moisture, since it decomposes the 



