128 Analysis of the Pittsburgh Mineral Spring, 



look for any metallic salt, and we have only to determine 

 the quantity of iron which is thus suspended. 



Experiments 1 and 3 have shown the presence of a con- 

 siderable quantity of carbonic acid gas. 



Experiments 1 and 4 show that the iron is held in solution 

 by this gas. 



Experiments 6 and 7 demonstrate the presence of muriate 

 acid combined with a base. 



Experiments 8 and 9 shew the presence of a small quanti- 

 ty of sulphuric acid and of lime. 



It now remains to confirm these, by evaporation and more 

 direct experiments, as well as to determine the quantity 

 of each substance in a given quantity of water. 



SECTION III. 



Examination of the gaseous contents. 



As many of the most important qualities of mineral wa- 

 ters arise from the gas with which they are impregnated, 

 there is no part of their analysis which requires more atten- 

 tion. In order to determine the quantity of this gas I pro- 

 ceeded in the manner which I have pointed out in my essay 

 on the mineral waters of Ballston and Saratoga, and which 

 I have uniformly found successful. A plate of the instru- 

 ment which I used on those occasions will be found in the 

 publication alluded to. It consists of a tin vessel, calculated 

 to hold one quart of water. A covering was soldered on it, and 

 no opening left except one at the top, to which was adapted a 

 small tube about half an inch long, and one third of an inch 

 in diameter. A graduated decanter was connected with 

 this which was filled with hot water. Heat was then ap- 

 plied to the tin vessel when the gas which was extricated 

 from one quart of water was collected in the glass vessel 

 graduated into cubic inches. I found that the whole of the 

 gas which was extricated from one quart of the water 

 amounted to eighteen cubic inches, which, when passed 

 through lime water, was entirely taken up by it, so that it 

 consisted entirely of carbonic acid gas. Some surprise may 

 be excited at finding so small a quantity of carbonic acid in 

 this water, when we compare it with the waters of Saratoga 

 and Ballston, but let it be recollected that they have no re- 

 semblance ; and if we refer to the analysis of the most eel- 



