268 



and vegetable matter contains hydrogen. In ordinary decomposition, 

 this gas is hberated; and if, in the nascent state (at the moment of being 

 set free from a previous combination,) it comes in contact with the sul- 

 phates, it decomposes them, imiting with the sulphur, to form sulphur- 

 etted hydrogen, or hydro-sulphuric acid. This is a very noxious gas, 

 and its foul odor is perceived in the exhalations from bilge water, cess- 

 pools, drains, &c. Hence the necessity of avoiding contact with organic 

 matter when the water contains the soluble sulphates. It should not be 

 conveyed through wooden logs, or pumped through wooden pumps. 

 The disinfecting property of chloride of Ume depends upon its power 

 to decompose and destroy this hydro-sulphuric acid. 



ANALYSIS. 



In conducting any analysis, the first object with the Chemist, is to 

 determine what substances are present. This is called the qualitative 

 examination, or analysis. In the case in question, an indefinite quanti- 

 ty was taken, and, having been divided into several parcels, the proper 

 tests were applied, for the detection of every substance liable to be pre- 

 sent in natural or mineral waters. This qualitative analysis resulted in 

 the detection of the following substances : 



No. One. 

 from iron pipe. 



No. Two. 

 from logs. 



No. Three, 

 from well. 



Silicic Acid (Flint,) I Present. 



Oxide of Iron, j Present. 



Lime, Present. 



Magnesia, Present. 



Potassa, -- Present. 



Soda, Present. 



Chlorine, Present. 



Sulphuric Acid, Present. 



Phosphoric Acid, Present. 



Carbonic Acid, | Present. 



AUumina, Present. 



Hydro-Sulphuric Acid, j 



Present. 

 Present. 

 Present. 

 Present. 

 Present. 

 Present. 

 Present. 

 Present. 

 Present. 

 Present. 

 Present. 

 Present. 



Present. 

 Present. 

 Present. 

 Present. 

 Present. 

 Present. 

 Present. 

 Present. 



Present, 



Present. 



Having thus fixed upon the presence of certain substances, attention 

 was next directed to the determining of the quantity of each of these 

 substances, or the quantitative analysis. 



The total quantity of solid matter, in a definite quantity of water, af- 

 ter filtration, was determined by evaporating to dryness 3500 grammes 



