198 SPRING?, RIVERS, CANALS. LAKES, 



acids of very different strengths. These experiments have afforded 

 the following results : 



o 



1. Solutions made in the cold, became charged more or less 

 readily with different quantities of mercury, according to the degree 

 of concentration of the nitric acid; but whatever the quantity of 

 mercury dissolved in the cold by the concentrated acid may be, no 

 part of it will he precipitated by mere water. He dissolved in the 

 cold two drachms and a half of mercury, in two drachms of ni- 

 trons-acid red and fuming, weighing one ounce four drachms and 

 five groins, in a bottle which contained an ounce of distilled water; 

 the combination took place with the utmost rapidity ; very dense 

 nitrous gas escaped, together with aqueous vapours, dissipated by 

 the heat of the mixture, amounting to more than one fourth of the 

 acid. This solution was of a deep green, and very transparent : 

 he poured a lew drops into half an ounce of distilled water: some 

 white stride were formed, which were dissolved by agitation, and 

 afforded no precipitate, though it was the most saturated solution 

 he could make in tlie.rold, and presented the greatest degree of 

 commotion, effervescence, and red vapours, during the combina- 

 tion of the mercury and acids. As it had deposited crystals, he 

 added two drachms of distilled water, which dissolved the whole 

 without any appearance of precipitation. With much greater safety, 

 therefore, may such solutions as have been made in the cold with 

 common nitric acid, and half their weight of mercury, be used in 

 the analysis of mineral waters, for they will never afford a precipi- 

 tate by the addition of mere water. 



2. The weakest nitric acid strongly heated on mercury, will dis- 

 solve a larger quantity than the strongest acid in the cold. The so- 

 lution, which is thick and of a light yellow colour, will appear thick and 

 oily, and will afford by standing, an irregular yellowish mass, which 

 may be changed into a beautiful turbitk by the addition of boiling 

 water ; this solution poured into distilled water, forms a very 

 abundant precipitate of a yellow colour, similar to turbith. A 

 solution made in the cold exhibits the same result, if it be strongly 

 heated, so as to disengage a large quantity of nitrous gas. These 

 solutions made with heat, ought therefore, to be excluded from the 

 analysis of mineral waters, because they are decomposable by dis- 

 tilled water. 



3, The two solutions appear to differ from each other in the 



