MINERAL WATERS, WELL WATERS, ETC. 217 



100 cub. cents, or grain measures of water, so that the 

 quantities of water employed may be determined by 

 measure. 



II. Carbonic acid and sulphuretted hydro yen- gases. 

 The apparatus represented by Fig. 25 is used to deter- 

 mine the quantity of the air (nitrogen and oxygen) 

 existing in the water. 



Fig. 25 



A flask of the capacity of 2 or 3 litres is filled with 

 the water as well as a tube suitable to collect the gases. 

 When the apparatus is thus completely filled with 

 water, the extremity of the bent tube is fastened under 

 a graduated bell-glass full of mercury, and arranged 

 over a mercury trough. The water is gently heated 

 until it boils, and the air passes off* with the stream 

 and the quantity is seen in the graduated bell-jar. 



The apparatus just described gives sufficiently exact 

 results, when only the relation of the nitrogen and 

 oxygen dissolved in the water is to be determined. 

 It presents serious difficulties when carbonic acid is 

 also to be determined ; the water which is condensed 

 in the. tube being found in a sufficient quantity 

 19 



