the Substances usually present in Water. 43 



To discover the amount of combined carbonic acid, the greater part 

 of a portion of the water is boiled off; the earthy carbonates and 

 iron are thus precipitated. This precipitate is treated as above, over 

 mercury in a tube, to give the carbonic acid combined with the 

 earths or oxide of iron ; or, should it be unmixed carbonate of lime, 

 it may be ignited, and the carbonic acid estimated directly from 

 its weight. 



Should the water contain carbonic acid in union with potass 

 or soda, it may be then separated by pouring in solution of pure 

 nitrate of lime. The precipitate is carbonate of lime, from which 

 the carbonic acid may be easily calculated. 



To the solution now freed from carbonates, nitrate of barytes 

 is added. From the weight of the precipitate is got that of the 

 sulphuric acid. Should boracic acid be present, the precipitate will 

 contain borate of barytes, which, previous to weighing it, must 

 be dissolved out by digestion in diluted nitric acid. 



Into the solution thus freed from sulphates, nitrate of silver is 

 poured to separate the muriatic acid. Chloride of silver precipitates, 

 which must be fused into a horn-like substance, before it is weighed 

 to estimate the chlorine in it. As, in case of boracic acid in the 

 water, it may be contaminated with borate of silver, it must also be 

 previously purified by the action of diluted nitric acid. 



The only good method of separating nitric acid is the following : 

 Concentrate the water highly by evaporation. Remove the muriatic 

 acid in it by the action of sulphate of silver. Then add to it in a 

 small retort pure sulphuric acid. Distil to dryness into a receiver 

 in which is water containing pure carbonate of barytes diffused 

 in it. Nitrate of barytes is formed, sulphuric acid is added to 

 this in solution, and from the weight of the precipitated sulphate 

 of barytes, the equivalent weight of the nitric acid is inferred. 



The boracic acid may be obtained by evaporation of the water to 

 dryness, adding sulphuric acid in quantity sufficient to decompose 

 the saline matter present, dissolving out the boracic acid by alcohol, 

 adding ammonia to prevent any of it from passing off with the 

 alcoholic vapours, evaporating to dryness and ignition, by which 

 pure boracic acid alone remains. 



The bromine will be found associated with the chlorine precipitated 



