30 WATER 



transmitted to the laboratory. Special forms of apparatus have 

 been designed for this purpose. That figured in Chapter VI 

 under Milk Examination is a very convenient form. As used 

 by the writer, the inner chamber is made to take exactly four 

 bottles and tins as described below. 



The bottles fit tins into which they can just slip (Fig. 4). 

 The bottom of the tin is provided with a layer of cotton wool 

 and then a piece of asbestos cardboard. Several thicknesses of 

 asbestos cardboard are also fitted into the cover of the tin so 

 that, when in place, the bottle is firmly in contact with the 

 asbestos above and below. The bottles, with their stoppers 

 rather loosely inserted, should be sterilized in their tins. The 

 tins, after sterilization, are not opened until immediately before 

 the sample is collected. 



To take samples from various depths, several different forms 

 of apparatus have been devised. The ordinary collecting bottle 

 may also be used for this purpose. It is tied into a leaden 

 cage, and lowered to the required depth by catgut or string 

 attached to the cage. The loosened stopper is then removed 

 by a jerk upon a second string, previously tied to the stopper, 

 and the sample collected. 



In collecting samples from a reservoir, lake or river, plunge 

 below the surface before removing the stopper, thus avoiding 

 scum and surface contaminations. If from wells with pumps, 

 pump away a considerable quantity of water before collecting 

 the sample ; while, if a complete investigation is required, a 

 second sample should be obtained after several hours' pumping. 

 If from a tap, allow the water to first run to waste for five to ten 

 minutes. In collecting samples from a tap it is necessary to 

 remember that the interior of the tap may not be clean and care 

 must be taken to obviate this source of error. As far as possible 

 samples should be taken from rising mains and always with 

 as little intervention of pipes as is practicable. 



The stopper should only be removed at the actual time of 

 collection, great care being taken that the part of the stopper 

 which goes into the bottle is neither touched nor brought into 

 contact with anything, apart from the bottle or water. It must 

 be held by its free end, and at once replaced and screwed in 



