26o C.-E. A. WiNSLOW AND E. E. LOCHRIDGE 



The garnets were dried for 12 hours at 7° and exposed in platinum 

 sieves to the action of the disinfectant solution studied. The tem- 

 perature was kept constant at 18° C. during the experiment, and after 

 the desired time had elapsed the excess of disinfectant was carefully 

 removed by appropriate reagents (neutralization of acids and bases, 

 precipitation of heavy metals with ammonium sulphide, etc.). After 

 thorough rinsing, the garnets were shaken up with water to detach 

 the cells, which were then plated on agar. No attempt was made 

 accurately to fix a killing point by testing a long series of dilutions 

 of each disinfectant, and no exact calculations were made of dissocia- 

 tion. In a general way, however, the number of spores of B. anthracis 

 which developed after treatment for a given time varied inversely 

 with the amount of dissociation. Thus in the study of metallic salts 

 it appeared that the activity of various compounds of mercury, 

 silver, copper, and gold was greatest in those actively dissociated, 

 and decreased in those which yield less free metallic ions. Solutions 

 of mercuric chloride and silver nitrate, in alcohol, where no dissocia- 

 tion occurs, showed almost no disinfectant action. Furthermore, 

 the toxic action of a salt having poisonous metallic ions was markedly 

 diminished by the presence of a non-toxic salt of the same acid. 

 This is in accord with physico-chemical theory; in any solution the 

 ratio between the undissociated molecules and the product of free 

 anions and cations is constant, so that the addition of sodium chloride 

 to mercuric chloride keeps the proportion of chlorine ions the same, 

 but replaces a portion of the mercury ions by those of sodium. So 

 it appeared in Kronig and Paul's work that successive additions 

 of sodium chloride to mercuric chloride progressively increased 

 the number of colonies developing after the usual treatment. In 

 the study of different salts of the same metal it was found that the 

 acid radical may also exercise considerable influence on the disinfect- 

 ing power. 



With bases Kronig and Paul found the same general relation to 

 hold, ammonium hydroxid, which is weakly dissociated, being a 

 much less active disinfectant than the corresponding compounds 

 of potassium, sodium, and lithium. The authors noted in a general 

 way a diminution of disinfectant action in the presence of organic 

 compounds. The decrease was most marked with the halogens and 



