126 Analysis of the Pittsburgh Mineral Spring. 



qualities of the spring, I proceed to an experimental inquiry 

 into its chemical properties. 



SECTION I. 



Examination of the contents of the water by tests and 

 reagents. 



Expkr. 1, Litmus paper when dipped into the water fresh 

 from the spring has its color immediately changed from blue 

 to red, but this color is fugacious ; nor will the water when 

 boiled produce any such effect, a decisive proof that this 

 change was produced by the presence of uncombined car- 

 bonic acid gas, and not by a fixed acid. 



2. Paper stained with tumeric is not changed in color by 

 this water, nor could it well be expected as the carbonic acid 

 gas would repress the effect of this test. 



3. Lime water produces an immediate turbidness and pre- 

 cipitation when added to this water, yet a variety of circum- 

 stances are to be attended to in the application of this test. 

 The usual directions which are given are that the lime water 

 shall be added to it in equal quantity. This, however 

 if the mineral water is saturated with carbonic acid, as in 

 the case of the Ballston water, is too much, and if the 

 water contains but little carbonic acid, it is not sufficient to 

 decompose the same water ; in order therefore to ensure a 

 complete and permanent precipitation of the lime, it requires 

 four cubic inches of the water of this spring to decompose 

 three cubic inches of lime water. It is evident, therefore, 

 that the greater the quantity of carbonic acid gas, which is 

 contained in a mineral water, the less of that water is re- 

 quired to produce the requisite change, so that by observing 

 this rule, an experienced chemist can form a tolerable accu- 

 rate judgment of the quantity of carbonic acid contained 

 in any mineral water. 



4. Tincture of galls, when poured into a glass of this water 

 strikes an immediate purple color, which after standing for 

 some time, increases in intensity, but no such change takes 

 place if the water has been previously boiled. 



5. Prussiat of potash. — This test produces an immediate 

 change in the color of the water ; it first becomes green, 

 and after standing for some hours assumes a blue color. 



