262 BACTERIA, YEASTS, AND MOLDS 



is a very effective germicide, one part of formalin to ten 

 thousand parts of water being sufficient to destroy the vital- 

 ity 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 material 

 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 and must be carefully handled. In 

 recent years it has come to be used extensively by health 

 boards for disinfecting rooms. Formaldehyde gas is liber- 

 ated in considerable quantity and allowed to act in closed 

 rooms for a number of hours. To liberate the gas in 

 quantity various devices have been adopted. One of the 

 simplest means is burning what are known as formalin 

 candles, which can be lighted and left to burn in a room, 

 giving out quantities of formalin gas. Other methods 

 require special apparatus in the form of lamps, etc., and 

 are not within the reach of the ordinary householder. 

 The efficacy of this gas in disinfecting has been ques- 

 tioned. It appears to be about as efficient as sulphur, 

 and under some circumstances more so, though not an 

 absolute germicide in every case. It is probably the best 

 gas disinfectant known. 



Application of Disinfectants 



In determining the application of disinfectants two ques- 

 tions arise : (i) Where should the disinfectant be applied.' 

 (2) What is the proper disinfectant to apply.? In most 

 problems that confront the household there is little diffi- 

 culty in determining the place where the disinfectant 



