220 Mr. Brande on the Analysis 



equal to the saline contents in a quantity of the water denoted 

 by the number employed to indicate the specific gravity of dis- 

 tilled water. Thus suppose the specific gravity of the water 

 == 1.079, and that of pure water = 1.000, then 79 x 1.4 = 

 110.6 = saline contents in 1000 of the mineral water." 



This is a useful formula, but open to certain objections; and 

 as it is often of considerable importance to acquire a just know- 

 ledge of the proportion of foreign bodies in water, it is advisa- 

 ble to conjoin the above method with the following. 



3. Evaporate a given weight, say 1000 parts, to dryness, and 

 expose the residue for twenty-four hours to a temperature not 

 exceeding 300° upon a platinum capsule ; weigh it, and the 

 mean obtained from this and the former experiment, will give 

 the proportion of dry saline ingredients within an error of two 

 per cent. Thus suppose 1000 parts of the above- mentioned 

 water give by evaporation 114.4 dry residue, then 110.6 -f- 

 114.4 =: 225 -f- 2 = 112,5 r= quantity of saline matter in a 

 dry state (salts deprived of water of crystallization) existing in 

 the mineral water under investigation. 



4. Having by these preliminary operations ascertained the re- 

 lative quantity of foreign matter in the water under examination, 

 the nature of the substances present is next to be inquired into. 



The substances which have been found in mineral waters are 

 extremely numerous, but those which ordinarily occur, are the 

 following : 



Oxygen. 



Nitrogen. 



Carbonic acid. 



Sulphuretted hydrogen. 



Carbonate of lime. 



Carbonate of magnesia. 



Carbonate of iron. 



Muriate of magnesia. 



Sea salt. 



Sulphate of magnesia. 



Sulphate of soda. 



Sulphate of lime. 



