28 MEDICAL BACTERIOLOGY 



"Pour into a glass about 20 cc. of the fluid, and drop on the surface a few 

 centigrams of phenolphthalein in powdered form. Dakin's solution, correctly 

 prepared, gives absolutely no change in tint, while in the same conditions 

 Javelle water and Labarraque's fluid give an intense red coloration which 

 indicates in the latter two solutions the presence of free caustic sodium." 



Numerous preparations have been put forth to replace the D akin-Carrel 

 solution. None of them has as yet stood the test, except the one recommended 

 by Duret. His preparation depends upon the liberation of chlorine from mag- 

 nesium hypochlorite, instead of a sodium salt. This solution is more stable, 

 isotonic with blood serum, and as it has no alkali entering into its preparation, 

 the latter will be free from such contamination. The following is its formula as 

 published in the Journal of the American Pharmaceutical Association (page 

 241, March, 1917). 



Chlorinated lime 28 . oo Gm. 



Magnesium sulphate 18 . 20 Gm. 



Water IOOO.GO Gm. 



The two salts are triturated in a mortar and the water added gradually in small 

 portions. The solution is then filtered through cotton-wool. 



Solution of eusol, and chloramine, the coal-tar derivative containing 

 available chlorine, have been recommended recently by Dr. Dakin as valuable 

 disinfectants. 



A complete report of the use of chloramine in the treatment of infected 

 wounds may be found in the Journal of the A. M. A. July 7, 1917, page 27. 



The organic disinfectants are by far more numerous and indeed countless. 



Ethyl alcohol is one of the most common disinfectants of this class. By 

 many it is regarded of little value, but experiments recently carried out verify 

 the results of Harrington and Walker (Boston Medical and Surgical Journal, 

 vol. 148, p. 548). These men found that "unless the bacterial envelope contains 

 a certain amount of moisture, it is impervious to strong alcohol, but dried bac- 

 teria in contact with alcohol, containing from 30 to 60 per cent, of water, will 

 absorb the necessary amount of water therefrom very quickly and then the 

 alcohol itself can reach the cell protoplasm and destroy it." Adding small 

 portions of chloroform, ether and more commonly acetone (these acting as fat 

 solvent) is commonly practised. 



Coal tar has furnished many substances that possess disinfectant properties. 

 Much doubt still prevails as to the efficiency of numerous members of this 

 class on the basis of value assigned them due to laboratory tests, especially 

 since many of them have proven of little value in practice. Though this be a 

 fact, still there remains a large number which are available and possess a high 

 disinfectant value. 



Phenol, the most commonly used organic disinfectant, is commonly employed 

 as a wash in strengths from i to 5 per cent. 



Cresol, ortho-, meta and para, the mixture of the three gives rise to the 

 commonly used tricresol. These are more powerfully germicidal than phenol. 



