Aqueous Solutions of Acids and Alkalies. 299 



the condensation is equal to only one-thousandth part of the 

 bulk of the water, but it is equal to three times the bulk of 

 the uncombined anhydrous acid. 



It is curious to compare this chemical condensation with 

 that which is effected in water by simple pressure. A weight 

 of 1 lb. avoirdupois applied to a cube of water of the bulk of 



1 septem diminishes its height to the extent of 50 millionths, 

 whereas 1 lb. weight of sulphuric acid, = 14 test atoms, ap- 

 plied to 450 septems of water, = 28 test atoms, occasions a 

 condensation equal to 143 septems, and if applied to 100000 

 septems of water, it occasions a condensation equal to 1400 

 septems. 



If, as some chemists affirm, dilute solutions are not to be 

 held as chemical compounds, but only as mixtures of acid 

 and water, in what manner shall we account for this enor- 

 mous condensation ? We universally admit, as chemical com- 

 pounds, the hydrate of sulphuric acid with 1 atom of water 

 (oil of vitriol), and the crystallizable hydrate with 2 atoms of 

 water ; but when the compound contains more water than 



2 atoms, some of us, for that reason alone, begin to question 

 the occurrence of chemical action. Yet surely the evidence 

 afforded by progressive condensation is not to be disregarded 

 merely because the condensation occurs in a dilute liquor ? 

 and jf a condensation equal to ten septems is taken as a proof 

 of chemical action in the formation of the second hydrate, 

 how can we reasonably declare that a condensation equal to 

 a hundred septems, effected by the same quantity of acid, 

 but with more water, is evidence of no chemical action ? 



The rate of condensation does not seem to accord with any 

 arithmetical or geometrical progression. I cannot reduce it 

 to any useful formula. I can perceive no particular relation 

 that it bears to the real specific gravity of the solutions, nor 

 to their chemical strength, nor to the state of hydration of 

 the acid, nor to any other general principle. I am unable to 

 construct a formula with which to determine either the che- 

 mical strength of a solution from its specific gravity, or the 

 specific gravity from its chemical strength. But this pro- 

 bably arises from the fact that the subject has not been suffi- 

 ciently examined ; for a glance at the Tables cannot but 

 suggest the opinion, that the condensation effected by every 

 particular substance will have an invariable progression. 



In the mean time there is one particular in which we can 

 approach a little towards a knowledge of the laws that regu- 

 late specific gravities, and that is, in determining the exact 

 degree in which condensation increases the mean specific 

 gravity of a solution. What I have to say on this head ap- 



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