combinations of Oxymuriatic Gas and Oxygene , &c. 11 
and soda are hydrats, and the bodies formed by the combus- 
tion of the alkaline metals, are, as I have always stated, pure 
metallic oxides, (as far as our knowledge extends) free from 
water.* 
vescence took place, and after intense ignition for a few minutes, there was an addi- 
tional loss of weight of four grains and a half. The energy with which water 
adheres to certain bodies in other cases, is shewn by the experiments of M. Ber- 
thollet, Mem. d’ArcueU, tom. ii. page 47. Indeed it is impossible to say that a 
neutral compound, or a fixed acid is ever entirely free from water ; it is only the first 
proportions that are easily separated. If the proportions of water in common potash 
and soda were to be judged of from their loss of weight, in combining with boracic 
acid, it would appear to be from 19 to 20 per cent, in the first, and from 23 to 25 in 
the second. 
* After the experiments detailed in my two last papers, it may perhaps appear un- 
necessary, at least to those enlightened British chemical philosophers who have closely 
followed the progress of science, to offer any new evidences to prove that potassium 
and sodium are not hydrurets of potash and soda, particularly as M. M. Gay Luss ac 
and Thenard, the ingenious advocates of this notion have acknowledged, in the 
Moniteur to which I have before referred, that it is not tenable; but on a subject so 
intimately connected with the most refined departments of chemical philosophy, and 
with so many new objects of research, additional facts cannot be wholly devoid of use 
and application. 
Mr. Dalton, in the second volume of the work which he entitles “ A New System 
of Chemical Philosophy ,” of which he has had the goodness to send me a copy, has, 
I find in his first pages, adopted the idea that potash and soda are metallic oxides ; 
but in the latter pages has considered them as simple bodies, and the metals formed 
from them as compounds of potash and soda with hydrogene. He has given no facts 
in favour of this change in his opinion : his principal argument is founded upon the 
process in which I first obtained potassium. Common potash is a hydrat : when oxy- 
gene is procured from this by Voltaic electricity at one surface, and potassium at 
the other surface ; Mr. Dalton conceiving that this oxygene arises from the water, 
states that the hydrogene of the water must combine with the potash to form potas- 
sium. It is evident, that adopting such a plan of reasoning, lead or copper might be 
proved to be hydrurets of their oxides ; for when these metals are revived from their 
aqueous acid solutions, oxygene is produced at the positive surface, and no hydrogene 
at the negative surface. 
In my first experiments for producing potassium and sodium, I used a weak. 
