EXPERIMENT STATION BULLETINS 339 



ou large, raw, and mucous surfaces, Avliere there is clanger of absorption resulting 

 in general mercuric poisoning. Mercuric chloride is a very strong poison, and 

 should always be treated as such. 



Carbolic Acid (Phenol).— Carbolic acid in its pure form is crystalline. The 

 crystals may be easily liquified by the application of heat. If allowed to cool again 

 it will recrj'stalize, unless water to the amount of five per cent of the carbolic 

 acid is added to prevent recrystalization. In this ninety-five per cent form, jmre 

 carbolic acid is usually purchased at drug stores and is doubtless more convenient 

 for use. If more water than is necessary to prevent recrystalization be added, there 

 will be a separation of water and acid until the acid becomes diluted to the amount 

 of five per cent of the diluent water. This will account for the ditficulty with 

 which a six per cent or larger per cent solution of carbolic acid is made. 



Carbolic acid has long been used as a disinfectant and germicide and is still 

 regarded as possessing great value. The ease with which it may be handled and 

 the effctiveness of its action may account for its popularity and its wude use. 



Koch has demonstrated that anthrax spores were not affected by a one per cent 

 solution for fifteen days, but that a two per cent solution prevented development. 

 Crookshank has reached the conclusion, after careful work, that carbolic acid is by 

 far a more valuable germicide or disinfectant than mercuric chloride, and he would 

 use it more generally than the latter substance. According to Sternlberg, pus cocci 

 are destroyed by a solution of one to one hundred and twenty-five in two hours. 

 The germs of Asiatic cholera, typhoid fever and pus cocci are killed by a one per 

 cent solution, but a one-half per cent solution fails in most cases. The investigation 

 of Schill and Fischer indicate that a three per cent solution will disinfect tuber- 

 culous sputum in twenty-four hours. If there is no danger of poisoning and a 

 drastic disinfectant is desired, a five per cent solution is recommended, but if ap- 

 plication is to be made on the surface of the body or parts of the body, nothing 

 stronger than two or three per cent should be used. Upon mucous and raw sur- 

 faces, one-half per cent is as strong as is safe to use as an antiseptic. 



Formalin— (Formal, formaldehyde.)— This agent is of recent development. Tests 

 made with it, however, have proved its great worth as a germicide, disinfectant 

 and antiseptic. It promises to supplant some of the more prominent agents now in 

 tise. It is a gas soluble in water to the extent of forty per cent, and upon the 

 market it will be found in aqueous solution. In this form it may be used as a 

 liquid agent, or it may be regenerated by a suitable apparatus into the gaseous 

 form and used where sulphur fumes are now employed. 



All tests made of this substance in gaseous form give it the foremost place among 

 practical gas disinfecting agents. This place has been maintained by it through all 

 the applications made, and it now holds in practical disinfection an undisputed 

 position. 



Roux and Trillat made use of a great variety of materials upon which many 

 well-known pathogenic germs were placed and subjected them to the action of 

 formalin. Tliese germs were placed in widely separated parts of a large room. 

 Their result.s indicate a most favorable germicidal action. They state that the 

 destruction of pathogenic bacteria submitted to the tests was absolute in a space of 

 fourteen hundred cubic meters when the germs were freely exposed to the vapors 

 of formaldehyde; that the sterilization of the dust of the air and of walls submitted 

 to the test can be considered as practically absolute. Pfuhl has also contributed a 

 series of experiments which elaborate furtlier upon the usefulness of this gas 

 disinfectant. Hammer and Feitter, in their work upon the specific action of forma- 

 lin on the anthrax bacillus, have proved that a two to five per cent solution of 

 formalin is effective. Novy and Waite have compared it with sulphur and have 

 demonstrated that formalin has many advantages over sulphui*. They say: "One 

 apparatus is sufficient, regai'dless of the size of the room or rooms to be disinfected. 

 The same apparatus can be used for almost any number of disinfections in the 

 course of a day. The distillation of formalin into an ordinary room need not take 

 more than twenty-five or thirty minutes. It is easily portable, since it is very light 

 and is not voluminous. Inasmuch as it remains on the outside of the room before 

 the eyes of the operator, there is absolutely no danger of fire or explosion. The 

 apparatus, formalin and fuel are inexpensive." These same investigators state 

 that one hundred and fifty cubic centimenters will suffice to disinfect one thousand 

 cubic feet of space, when liberated as a gas. 



Sulphur.— This material has a very favorable history to bear testimony to its 

 effectiveness. There is no means of knowing how much it has wrought for man- 

 kind. Its value may be partly attested by the constant and widespread employ- 

 ment made of it. Furthermore, experiments confirm what experience has credited 



