STUnr OF WATER. 429 



bulbs may be blown and allowed to cool, but not sealed. 

 After a sufficient number of them are prepared they are 

 taken, one at a time, and gently warmed over the flame ; 

 while still \rarm the extremity of the stem is dipped 

 into distilled water and held there until a few drops 

 have passed up into the bulb ; this is then care- 

 fully boiled, or rather, completely vaporized, over the 

 flame, and while the steam is still escaping the point is 

 sealed in the gas flame. All air will have thus been 

 replaced by water vapor, and if the point of the stem 

 be now broken off under water the bulb will fill quickly 

 and completely. It is not desirable to fill them oom- 

 pletely, but rather to only about three-fourths of their 

 capacity, as when full it is difficult to empty them with- 

 out contaminating the contents. They are emptied by 

 gently warming over a gas or alcohol flame. 



A number of them may be made, sealed, and kept 

 on hand. They are sterile" so long as they are sealed, 

 because of the heat that is employed in their manu- 

 facture. 



When a sample of water is to be taken, the point of 

 a bulb is simply broken off with sterilized forceps under 

 water at the place from which the sample is to be pro- 

 cured and held there until the necessary amount has been 

 obtained. This may serve as a sample from which to 

 prepare plates or Esmarch tubes on the spot, or the tip 

 of the stem may be resealed in the flame of an alcohol 

 lamp, the bulb packed in ice, and transported in this 

 condition to the laboratory. 



Another very simple and useful device for collecting 

 water samples is that recommended by Kirschner. It 

 consists of a piece of glass tubing of about 5 or 6 mm. 

 inside diameter and 36 cm. long, bent in the form of a 



19* 



