288 BACTERIA, YEASTS, AND MOLDS 



applied dry if the material which is to be disinfected con- 

 tains moisture, but it acts only in the presence of mois- 

 ture and should usually be dissolved in water. A solution 

 of one part to twenty-five of water (one pound to six 

 gallons) will be found to be very eflScient in disinfecting 

 walls, floors, furniture, etc. Chloride of Ume is also one 

 of the most efficient disinfectants for water. When added 

 in very minute quantities, only one part of chlorine to a 

 million of water, it kills the disease germs and is perfectly 

 harmless in the water. It is very widely used to-day for this 

 purpose and its use is extending rapidly. Common slacked 

 lime, which is occasionally used, is of httle value as a 

 disinfectant. 



Formalin. This material, as purchased, looks like water, 

 and consists of a poisonous gas dissolved in water. The 

 liquid itself is a very effective germicide, one part of forma- 

 lin to ten thousand parts of water being sufficient to destroy 

 the vitality of bacteria. Formalin has no more injurious 

 action upon clothing than common water would have. 

 Hence it may be used very freely in disinfecting any ma- 

 terial that can be soaked in water. Its general use for 

 washing is hardly practicable, because it gives off a gas 

 that is very injurious to the eyes. It is also quite irritating 

 to the skin, and must be carefully handled. For these 

 reasons it is less widely used in the home than certain 

 other disinfectants. 



Creosote Disinfectants. A class of products derived from 

 coal tar and going under the general name of creosote 

 preparations are sold under a great variety of trade des- 

 ignations. They are all much alike in appearance and 

 properties, — brown, oily-looking liquids, having a strong, 



