254 Value of Antiseptics 



phenol with a melting point of 4o.5C., be used, as only such is entirely 

 free from impurities. The Eighth Revision of the U. S. Pharma- 

 copoeia declares phenol with a melting point of 4oC. to be pure and 

 that is the quality that may be accepted as the standard. 



The phenol used at the Hygienic Laboratory is Merck's "Silver 

 Label." The standard dilution, made by the U. S. P. method 

 (Koppeschaar), contains exactly 5 per cent, of pure phenol by weight, 

 in distilled water. From this stock solution, the higher'dilutions are 

 made fresh each day for that day's tests. 



2. The Solution to be Tested. A 5 per cent, solution is made by 

 adding 5 cc. of the disinfectant to 95 cc. of sterile distilled water 

 with a standardized 5 cc. capacity pipet. After filling the pipet, 

 all excess of the disinfectant on its outside is wiped off with sterile 

 gauze. The contents of the pipet are then delivered into a cyl- 

 inder containing 95 cc. of sterile distilled water and the pipet 

 washed out as clean as possible by aspiration and blowing out the 

 contents into the cylinder. The contents of the cylinder are then 

 thoroughly shaken. 



3. The Test Organism selected is Bacillus typhosus. Before be- 

 ginning the tests, the organisms in bouillon culture should be trans- 

 planted to fresh media every twenty-four hours for at least three 

 successive days. In making the transfers one loopful of a 4-mm. 

 platinum loop is carried over. In exposing the culture to the dis- 

 infectant, Jf cc. of the culture is always added to 5 cc. of the 

 diluted disinfectant, the amount being measured by pipets graduated 

 in tenths of a cubic centimeter. 



4. The Inoculating Loops. These loops are made of No. 23 U. S. 

 standard gauge platinum wire, each loop being 4 mm. in diameter. 

 There should be four, and preferably six, such loops mounted in 

 the usual glass handles, ready for use. In order to facilitate their 

 sterilization, a special holder is used. 



5. The Water-bath. As variations in the temperature of the 

 disinfecting solutions hasten or retard their destructive action, a 

 temperature of 2oC. has been arbitrarily adopted as the standard. 

 For its maintenance the following simply constructed water-bath 

 has been devised. It consists of a wooden box 20 inches deep, 21 

 inches long and 21 inches wide. Inside this box a i4-quart agate- 

 ware pail, 10 inches deep, is placed and saw-dust is well packed 

 around, sufficient being placed in the bottom of the box to bring 

 the rim of the pail on a level with the top of the box. A tightly 

 fitting wooden cover, so made that the edges project slightly over 

 the rim, is placed over the pail. In the cover are a sufficient number 

 of holes for the seeding tubes, a thermometer, and the tube contain- 

 ing the culture. About 3 inches below the rim of the pail a 

 false bottom of wire gauze is placed; this is for the seeding tubes, 

 etc., to- rest on; Water is placed in the pail to within half an inch 

 of the top. When an experiment is about to be made the tempera- 



