140 STERILIZATION AND DISINFECTION 
Carbon. Renon (1914) produced colloidal carbon electrolytically 
so that the size of the particles was 4 to Guz. He studied the antiseptic 
properties by measuring the acidification of milk. The antiseptic 
action increased with the amount of carbon. 
Orcantc CoMPOUNDS 
The infinite number of possibilities for securing compounds de- 
structive to bacterial life renders a discussion of the organic compounds, 
in this connection, rather difficult. Kligler (1918) has made a study 
of the action of aniline and some of its derivatives and of the triphenyl- 
methane dyes on bacteria. He stated from this investigation that 
the action on bacteria might be a function of the benzine nucleus and 
in the case of the dyes a function of the quinoid structure of the nucleus. 
Increasing the number of alkyl radicals increased the antiseptic proper- 
ties. ‘‘ The antiseptic power is enhanced to a greater extent by an 
ethyl than by a methyl group and the second alkyl produces a pro- 
portionately greater increase than the first. J+ appears that the relative 
position of the introduced group may be a factor in determining the 
relative improvement in the effectiveness of the compound.” An 
interesting fact is mentioned by Kligler that the Gram positive bacteria 
are more susceptible to the aniline dyes than are the Gram negative 
bacteria. 
Alcohol. Ethyl alcohol is usually used. It precipitates proteins 
unaltered and if they are allowed to remain in contact with the alcohol 
they are changed. The precipitation is probably due to dehydration. 
The greatest disinfective power is secured in strengths of between 50 
and 70 per cent. These solutions contain sufficient water for the 
coagulation of the protein. Beyer (1912) found that concentrations 
of alcohol under 60 per cent and over 80 per cent were practically 
worthless as disinfectants. Absolute alcohol, on account of its drying 
action exhibited a drying and preserving action. Frey (1912) found that 
treatment with various concentrations of alcohol influenced the swelling 
and solubility of protein in water. Alcohol diluted to 10 per cent 
dissolved a little of the protein; above 20 per cent of alcohol solution 
of the protein stops and swelling decreases; above 90 per cent the 
protein dissolves. The greatest action of alcohol on protein is at 60 to 
70 per cent while the greatest disinfecting power is 70 per cent. Frey 
explains the use of alcohol as a disinfectant in the irreversibility of the 
precipitation of protein after treatment in alcohol. 
