218 Dr. Marcet on an Aluminous Chalybeate Spring, 



§ III. Prelminary Experiments on the effects of Reagents, 



A. Paper stained with litmus was distinctly reddened by the 

 water. 



B. Paper stained with Brazil-wood was changed to a deep 

 purple. 



C. When agitated in contact with the air, or repeatedly poured 

 from one vessel into another, the water became turbid, and on stand- 

 ing deposited reddish flakes. 



D. On applying heat to a portion of the water just uncorked, and 

 boiling it quickly^ till it was reduced to one half or even one third of 

 its original bulk, no precipitation whatever took place ; but on con- 

 tinuing the evaporation, a white feathery crystalline substance 

 appeared on the surface of the fluid, and on pushing the process 

 still further, a saline matter of a pale yellowish green colour appeared, 

 which continued to increase till the whole was reduced to a dry yel- 

 lowish mass. These were the phenomena observed with water 

 recently uncorked ; but when, previous to the evaporation, it had: 

 been for some time exposed to the air, or when the evaporation was 

 conducted very slowly, an appearance of reddish flakes was the first 

 circumstance observed. 



E. The mineral acids produced no obvious change in the water. 



F. Oxalic acid produced a slight yellowish tinge ; but no imme- 

 diate precipitation or turbidness. 



G. Oxalat of ammonia, in small quantity, likewise produced a 

 yellow colour, without precipitate : but on adding more of this test 

 a white precipitate appeared. 



H. Prussiat of potash and infusion of galls produced abundant 

 precipitates, the one blue, and the other black or dark purple j and 



