364 APPENDIX 



COMMON DISINFECTANTS 



Mercuric chloride : (HgCl 2 ) White crystals. 



Synonyms: mercury bichloride, corrosive sublimate, 

 bichloride of mercury. 



The stock solution (40% HgCk in HC1) is prepared by 

 mixing 1 part mercuric chloride with 2.5 parts commercial 

 hydrochloric acid. This dissolves readily and aqueous 

 solutions of any desired dilution may be made from it much 

 more quickly than by the use of the salt. 



The pure salt is soluble in 16 parts of cold water and 3 

 parts of boiling water. 



Mercuric chloride 1 : 1000, the solution commonly used 

 in the laboratory for disinfecting purposes, is prepared by 

 adding to 2.5 c.c. of the stock solution, sufficient dis- 

 tilled water to make 1000 c.c. of solution. 



As a germicide, mercuric chloride acts in solution by 

 combining chemically with the protein of the microorganisms. 

 Therefore its efficiency varies in inverse proportion to the 

 amount of dead organic matter present. 



Mercuric chloride is exceedingly corrosive as is also 

 the acid in which it is originally dissolved; therefore it 

 should not be placed in metal containers or agateware 

 pails, cups, etc., if the enamel is chipped sufficiently to 

 expose the metal. 



Remember that mercuric chloride is a DEADLY POISON! 

 Great care must be exercised in properly labelling all bottles, 

 etc., containing it. 



Phenol: (CeHsOH) long colorless crystals that become 

 pink upon exposure to light and air. 



Synonyms: Carbolic acid, phenic or phenylic acid, 

 phenyl hydrate, hydroxybenzene (or -ol). 



The stock solution (95% phenol) is prepared by adding 

 1 part of water to 19 parts (by weight) of crystalline phenol. 

 Solution may be hastened by placing the vessel containing 

 the crystals in a dish of warm water, 



