144 ANTISEPTICS 



the aromatic bodies are associated with their chemical constitu- 

 tion. Thus among the cresols the ortho- and para-bodies re- 

 semble each other in general chemical properties, and stand apart 

 from metacresol ; they also are similar in antiseptic action, and 

 are much stronger than the meta-body. The same may be 

 observed in the other groups of ortho-, meta-, and para-bodies. 

 Again, such a property as acidity is important in the action of a 

 substance, and, generally speaking, the greater the avidity of an 

 acid to combine with an alkali, the more powerful an antiseptic 

 it is. With regard to oxidising agents and reducing agents, 

 probably the possession of such properties has been overrated as 

 increasing bactericidal potency. Thus in the case of such re- 

 ducers as sulphurous acid and formic acid, the effect is apparently 

 chiefly due to the fact that these substances are acids. Formic 

 acid is much more efficient than formate of sodium. In the case 

 of permanganate of potassium, which is usually taken as the 

 type of oxidising agents in this connection, it can be shown that 

 the greater amount of the oxidation which takes place when this 

 agent is brought into contact with bacteria occurs after the 

 organisms are killed. Such an observation is, however, not 

 conclusive as to the non-efficiency of the oxidation process, for 

 the death of the bacteria might be due to the oxidation of a 

 very small part of the bacterial protoplasm. Apart from the 

 chemical nature of antiseptic agents, the physical factors con- 

 cerned in their solution, especially when they are electrolytes, 

 probably play a part in their action. The part played by such 

 factors is exemplified in the important fact that a strong solution 

 acting for a short time will have the same effect as a weaker 

 solution acting for a longer time. From what has been said it 

 will be realised that the real causes of a material being an 

 antiseptic are very obscure, and at present we can only have a 

 remote idea of the factors at work. 



The Actions of certain Antiseptics. Here we can only 

 briefly indicate certain results obtained with the more common 

 members of the group. 



Chlorine. All the halogens have been found to be powerful 

 antiseptics, but from the cheapness with which it can be produced 

 chlorine has been most used ; not only is it the chief active 

 agent in the somewhat complex action of bleaching powder, but 

 it is also the chief constituent of several proprietary substances, 

 of which " Electrozone " is a good example. This last substance 

 is made from electrolysing sea -water, when magnesia and 

 chlorine being liberated, magnesium hypochlorite and magnesium 

 chloride are formed. In the action of this substance free hypo- 



