DESTRUCTION OF BACTERIA BY CHEMICALS. 165 
forms about one-third the strength of pure carbolic 
acid. 
Chloroform. This substance, even in pure form, does 
not destroy spores, but it does bacteria in vegetative 
form, even in 1 per cent. solution. Chloroform is used 
practically in sterilizing and keeping sterile blood-serum, 
which can be used later for culture purposes by driving 
off the chloroform. 
Iodoform. This substance has but very little destruc- 
tive action upon bacteria; indeed, upon most varieties 
it has no appreciable effect whatever. When mixed 
with putrefying matter, wound discharges, etc., the 
iodoform is reduced into soluble iodine compounds, 
which partly act destructively upon the bacteria and 
partly unite with the poisons already produced. 
Carbolic Acid (C,H,OH). A solution having 1 part 
to 1000 inhibits the growth of bacteria; 1 part to 400 
kills the less resistant bacteria, and 1 part to 100 kills 
the remainder. A 5 per cent. solution kills the less 
resistant spores within a few hours and the more 
resistant in from one day to four weeks. A slight 
increase in temperature aids the destructive action; 
thus, even at 37.5° spores are killed in three hours. 
A 3 per cent. solution kills streptococci, staphylococci, 
anthrax bacilli, etc., within one minute. Carbolic acid 
loses much of its value when in solution in alcohol or 
ether. An addition of 0.5 HCl aids its activity. 
_ Carbolic acid is so permanent and so comparatively 
little influenced by albumin that it is rightly widely 
used in practical disinfection even in places of more 
powerful substances. 
Cresol [C,H,(CH,)OH] is the chief ingredient of the 
so-called ‘‘ crude carbolic acid.” This is almost in- 
