CATARACTS, AND INUNDATIONS. 207 



be acidulous, it emits bubbles, as soon as the beat first begins 

 to act; in proportion as the carbonic acid is disengaged, a pellicle 

 is formed, with a deposition of calcareous earth, and carbonat of 

 iron. These first pellicles are succeeded by the crystallization of 

 sulphat of lime; and lastly, the muriats of potash and soda crys- 

 tallize in tubes at the surface, but the deliquescent salts are not ob- 

 tained but by evaporation to dryness. 



The residue must then be weighed, and put into a small phial, 

 with three or four times its weight of aikohol: the whole being agU 

 tated, and suffered to subside for some hours, must be filtrated, and 

 the atkohol preserved separate. The residue on which the spirit 

 has not acted, must be dried in a gentle heat, or in the open air; 

 when perfectly dry it must be weighed, and the loss of weight will 

 show what quantity of calcareous or magaesian muriat was con- 

 tained, because these salts are very soluble in alkohol. \\ r e shall 

 presently speak of the method of ascertaining the presence of these 

 two salts in the spirituous fluid. 



The residue, after treatment with alkohol, and drying, must be 

 agitated with eight times its weight of cold distilled water, and fil- 

 tered. After some hours standing, the residue is to be dried a se- 

 cond time, and boiled half an hour in four or five hundred times its 

 weight of distilled water; this last residue, after filtration, consists 

 of that which cold or boiling water is insufficient to dissolve. The 

 first water contains neutral salts, such as sulphat of soda, or of mag- 

 nesia ; the muriat of soda, or potash and the fixed alkalis, espe- 

 cially soda united with carbonic acid : the large quantity of boiling 

 water scarcely contains any substance but suiphat of lime. There 

 are therefore four substances to be examined, after these diffe < t t 

 operations on the matter obtained by evaporation, i. The residue 

 insoluble in alkohol, and in water of different temperatures. 2. The 

 salts dissolved in alkohol. 3. The salts dissolved in cold water. 

 4, and lastly, Those dissolved in boiling water. We shall now pro- 

 ceed to the experiments necessary to ascertain the nature of these 

 different substances. 



1. The residue which has resisted the action of the alkohol and 

 water, may be composed of calcareous earth, of carbonat of magrne- 

 sia and iron, ofaluiniue, ami of quartz. These two last substances 

 are seldom found in waters, but the three first are very common; 

 brown, or more or less deep yellow colour, indicates the presence 



