FORMALDEHYDE 189 



are not as effective as corrosive sublimate, and have to be used in 

 much stronger solutions when they are very poisonous; but they are 

 quite penetrating, and their value is not decreased by the presence 

 of albuminoid bodies, which gives them a wide range of application. 

 Carbolic acid is generally used in 3 to 5 per cent, solutions. Its 

 effect is very much increased by warming it to about 40 C., or by 

 the addition of hydrochloric acid, but not by the addition of alcohol. 

 Other bodies of the carbolic-acid group used as disinfectants are the 

 creosotes (ortho-, meta-, and para-creosote, the mixture known as 

 tri-creosote), creolin, and lysol. For the cleansing of woodwork, floors, 

 w^alls, etc., Nocht's carbol-soap solution is highly recommended. It is 

 prepared as follows : Dissolve 6 per cent, soft soap in hot water and 

 add to the hot solution 5 per cent, of raw (100 per cent.) carbolic 

 acid. Should any drops of tar form they should be removed and 

 only the clear solution used. It does not stain and cleanses wood- 

 work thoroughly. 



Formaldehyde. Formaldehyde is the aldehyde 1 of methylic alcohol. 

 It is a gaseous body of the chemical formula CHOH. It is found in 

 commerce in the form of a watery solution, which should contain 

 forty volumes of the gas per one volume of water. This solution in 

 addition to being simply called formaldehyde is also known under 

 a variety of proprietary names, such as formol, formalin, etc. When a 

 solution of formaldehyde is warmed, and often merely upon standing 

 undisturbed, a part of the gaseous body becomes polymerized, which 

 means that several molecules unite to form a larger molecule. Gen- 

 erally three molecules of formaldehyde unite and form a polymer- 

 ization product with the formula (H CHO) 3 . This body is known 

 as trioxymethylene, para-formaldehyde, or simply as paraform. It is in- 

 soluble in water, and forms a white sediment in the vessel containing 

 the formaldehyde solution. This chemical change is important, 

 because such a white precipitate or sediment indicates that a formalin 

 solution has lost much of its formaldehyde, that its value as a fluid 

 or gaseous disinfectant has become weakened, and that it must be 

 used afterward with a proper knowledge and consideration of this 

 change. In making up formalin solutions it must always be remem- 

 bered that the best commercial product contains not more than 40 per 

 cent, of the disinfectant itself. Hence, if a 4 per cent, formalin solu- 

 tion is recommended for a certain procedure it must be prepared 

 by taking one part of formalin and nine parts of water, not one part 

 of formalin and twenty-five parts of water. Paraform is also used 

 as a disinfectant, but according to a different method from that 

 employed with the gaseous formaldehyde dissolved in water. The 

 germicidal effect of a 4 per cent, formalin solution used as a 

 disinfectant is about equivalent to a 1 to 1000 solution of corrosive 



1 An aldehyde is a body formed by the oxidation of a primary or secondary alcohol, that is, 

 by the substitution of two or one H atom in the alcohol by one O atom. 



