SPRINGS, RIVERS, CANALS, LAKES, 



would falsify the result. This precaution, which is of great importance 1 

 in, the use of all re-agents, is likewise mentioned by Bergman am! 

 Gioanetti. To these may be added another observation concerning 

 the use of ammoniac. As it is a matter of considerable difficulty 

 to preserve ammoniac in the state of perfect causticity, though it is 

 necessary to be had in such a state, for the analysis of mineral 

 waters, a very simple expedient may be applied in this case. 

 It is to pour a small quantity of ammoniac into a retort, whose neck i 

 plunged in the mineral water; when the retort is slightly heated, the 

 ammoniacal gas becomes disengaged, and passes highly cautic into the 

 water* If it occasions a precipitate, it may be concluded that the 

 mineral water contains sulphat of iron, which may be known by the 

 colour of the precipitate, or otherwise that it contains salts, with 

 base of aluminous or magnesian earth. Generally this precipitate 

 is formed by the chalk which was held in solution in the water, by 

 means of the carbonic acid ; ammoniac absorbs this acid, and the 

 chalk is deposited. It is difficult to determine from the physical 

 properties of the earthy precipitate formed in waters by caustic am- 

 moniac, to which of the two last bases it is t< be attributed ; yet 

 the manner in which it is formed may serve to decide. Six grain* 

 of sulphat of magnesia were dissolved in four ounces of distilled wa- 

 ter, and six grains of alum in an equal quantity of the same fluid ; 

 through each of these solutions a small quantity of ammoniacal gas 

 was passed t the first solution immediately became turbid, while the 

 latter did not begin to exhibit a precipitate till twenty minutes after. 

 These mixtures were carefully included in well closed bottles. The 

 same phenomenon took place with the nitrats and murials of mag- 

 nesia and alumine, dissolved in equal quantities- -of distilled water, 

 and treated in the same manner. The quickness or slowness of the 

 precipitation of a mineral water by the addition of ammoniacal as, 

 therefore affords the means of ascertaining the nature of the earthy 

 salt decomposed by this gas. In general, salts, with base of mag- 

 nesia, are much more usually met with than those witli base of alu- 

 minous earth. Bergman has observed, that ammoniac is capable of 

 forming with sulphat of magnesia a compound in which a portion of 

 this neutral salt is combined, without decomposition, with a portion 

 of ammoniacal sulphat. This non-decoinpesed portion of su|. 

 pbat of magnesia may probably form, with the ammoniacal swlphi\t> 



