MERCURIC CHLORID 117 



with alcohol. It is well to place the generator on a table or box as 

 sulphur dioxid is heavier than air and hence tends to sink and would, 

 therefore, extinguish the flame if placed on the floor. 



Hydrocyanic acid gas is an extremely powerful insecticide, but 

 a poor germicide. It is used rather extensively against mosquitoes, 

 lice, bedbugs, and roaches, but on account of its highly poisonous 

 nature it must be used with extreme caution. It is effective against 

 bacteria no hardier than those of diphtheria and typhoid, but it 

 cannot be depended upon as a general disinfectant. 



Mercuric chlorid is one of the best known and most effective of 

 the metallic salt disinfectants. A solution of 1 to 1000 is ample 

 for the destruction of all non-spore-bearing bacteria, provided it 

 comes in direct contact with the organisms for some time. It is 

 especially valuable for disinfecting the hands and for washing floors, 

 woodwork, and furniture. It attacks metals and hence cannot be 

 used to disinfect them; it is rendered inactive by protein substances; 

 it acts on bacteria by a coagulation of the protoplasm. 



Its germicidal value as usually given* is too high. This is due to 

 the fact that it may inhibit the growth of bacteria and in the planting 

 of the cultures the metallic salt is carried over into the new medium, 

 there preventing growth but not necessarily killing the organism. 

 The explanation of this is given by Miss Chick who found that if 

 bacteria are subjected to the action of 1:1000, 1:10,000, or even 

 weaker solutions of mercuric chlorid, there is an interval during 

 which some at least of them may be resuscitated by the timely 

 administration of an antidote in this case a sulphid solution. If, 

 however, this antidotal treatment is not employed, no amount of 

 subsequent dilution beyond the limits of inhibition can prevent the 

 death of the organism. 



REFERENCES. 



Loeb: The Dynamics of Living Matter. 

 McClendon: Physical Chemistry of Vital Phenomena. 

 Dakin and Dunham: Handbook of Antiseptics. 



