INSECTICIDES, FUNGICIDES AND DISINFECTANTS 223 



tion and uncertain in its effects. It consists of a mixture of 

 coal tar oils, cresol and a very little phenol. The oil has 

 practically no disinfectant properties, although the odor is 

 popularly considered an indication that disinfection is being 

 accomplished. Its value as a disinfectant depends on the 

 content of cresol. When the cresol content is known, the 

 material should be diluted until it contains 2 per cent of 

 that acid. 



Cresol (CHsCeH-iOH), tricresol, straw-colored carbolic 

 acid, or liquid carbolic acid as it is variously termed, is found 

 on the market in various degrees of purity. Cresol as de- 

 scribed by the United States Pharmacopeia is a colorless 

 liquid having an odor similar to carbolic acid. On account 

 of a small amount of impurities it is usually sold of a 90 to 

 98 per cent purity. It should not contain less than 90 per 

 cent cresylic acid, as the cresol containing less amounts usually 

 carries enough coal tar oil to interfere with the solution of 

 the cresol in water. This material is relatively cheap and 

 well suited to disinfect yards, barns, and cars. The solu- 

 tion used for disinfecting should contain about 2 per cent of 

 cresol, which is said to be more effective than 5 per cent 

 carbolic acid. It is applied the same as the carbolic acid 

 solution. This material is not readily soluble in water, 

 hence care must be exercised to get a strong enough solution. 

 Its advantages are that it is cheap, does not destroy fabrics 

 or metals, is more effective than carbolic acid for destroying 

 spore -forming bacteria, and its action is not hindered by 

 albuminous substances. 



Cresol is made more soluble by mixing with an equal part 

 of linseed-oil-potash soap. Care must be taken to assure the 

 presence of 50 per cent of actual cresol in the mixture. 

 There should be 3 or 4 per cent of cresol in this sort of a 

 mixture when used for disinfecting, hence an increase in cost 

 over the straight cresol solution. 



Bichloride of Mercury. Bichloride of mercury (HgC^) 

 is a white crystalline, poisonous substance. It is prepared 



