1824.] Mineral Waters of Carlsbad. 137 



porating the water : in the water itself, however, they all exist 

 in the state of bicarbonates. 



Neither fluate nor phosphate of lime is soluble in water, but 

 their solubility in acids led me to suppose, that, in the Carlsbad 

 water they are held in solution by the uncombined carbonic 

 acid. To prove this, I diffused a quantity of recently prepared 

 and still moist fluate of lime through water, and impregnated 

 the liquid with carbonic acid gas. The filtered liquid, on being 

 heated to ebullition, deposited an exceedingly minute trace of 

 fluate of lime. I now put a quantity of carbonate of soda and 

 fluate of lime into another portion of water, and saturated the 

 mixture with carbonic acid. The solution in this experiment 

 became most distinctly turbid when boiled, and deposited fluate 

 of lime. It is obvious from this, that bicarbonate of soda is the 

 real solvent of the fluate of lime in the Carlsbad water. 



Phosphate of lime, both when precipitated by ammonia from 

 its solution in acids, and by lime water from a liquid containing 

 phosphoric acid, dissolves in water impregnated with carbonic 

 acid with much greater facility, and to a much greater extent, 

 than fluate of lime : and I could perceive no difference in this 

 respect, whether the water contained soda or not. Both the 

 phosphate and subphosphate of alumina are soluble to a slight 

 degree in water, and are precipitated by the addition of a con- 

 siderable quantity of any salt. No phosphate of alumina exists 

 in the sprudelstones ; it would appear that carbonic acid is its 

 solvent while in the water. Perhaps, also, the protoxide of 

 iron, in proportion as it becomes peroxidized, shares the acid 

 with the alumina, and renders it insoluble ; and, perhaps, the 

 lime may act in the same manner, at the instant when it ceases 

 to be a bicarbonate. 



Quantity of Carbonic Acid in the Carlsbad Water. 



The want of a mercurial trough, and of the other necessary 

 apparatus, prevented me from ascertaining this point on the spot 

 experimentally ; I hoped, however, to have attained my object 

 by less direct means, but, on making the attempt, I encountered 

 greater difficulties than had been at first anticipated. It ap- 

 peared to me, that if we could determine the nature and relative 

 amount of the gases which stand over the water in the subter- 

 raneous reservoir, it would be easy, from the knowledge we 

 possess respecting the solubility of gases, at given temperatures 

 and pressures, to calculate the quantity of carbonic acid in the 

 water which lies in contact with this atmosphere. A small 

 opening which has been made in the vault of the reservoir, in 

 the neighbourhood of the Sprudel, and from which gas and 

 water are discharged alternately, enabled me to collect a suffi- 

 cient quantity of gas for my purpose. On my return, I let up a 

 determinate quantity of this gas into a glass tube standing over 



