INORGANIC DISINFECTANTS 135 
Reichel (1909) explain the time clement in disinfection by assuming 
that the different eclls in a bacterial suspension possess different 
resistances—the weakest or less resistant cells dying first. If such 
were the case it is reasonable that most of the cells would possess the 
same resistance and consequently would succuinb at about the same 
time and that at each end of the process we would be dealing with the 
weakest (less resistant) and the strongest (most resistant) cells. Such 
a unimodal curve is usually secured where the element of chance or 
the law of probability enter. This same monomolecular law is followed 
among human beings where similar individuals and a multitude of 
causes of death obtain. The disinfectant may act as a catalyzcr since 
the process demands the presence of water. Where water is absent 
disinfection is inhibited. 
Factors which Influence the Value and Use of Disinfectants. The 
ideal disinfectant does not exist. If one could be found, it would con- 
form to the following charactcristics: 
1. Low cost. 
2. Non-toxicity to man and animals. 
3. Solubility in ordinary reagents in sufficient amounts to destroy 
bacteria. 
4, Minimum time for destruction of bacteria. 
5. Great penetrating power. 
6. Should be a stable compound under ordinary conditions. 
7. Should not react with cloth dyes or wood finishes. 
InoRGANIC COMPOUNDS 
Lusini (1912) has pointed out with regard to the cations that 
although the disinfecting property is not a function of the atomic 
weight the heavy metals exert the greatest action. With a few excep- 
tions, the disinfecting action increases with the chemical affinity of 
the combined elements. The alkali group is less powerful than the 
alkalin earth group. The last mentioned group does not fit in with the 
generalizations above since its disinfecting power is in inverse ratio 
to the atomic weight. Among the other elements of the periodic 
system iron has a lower activity corresponding to its low atomic weight; 
tin has a higher and lead still higher activity. This has been somewhat 
confirmed by other investigations. Bitter (1912) found that the fol- 
lowing metals exerted an antagonistic action toward bacteria drying 
on them. The intensity of action is in the following order: Copper, 
brass, silver, gold, platinum, lead, cast iron, steel, aluminum, nickel, 
