xxxviil Historical Sketch of the Physical Sciences, 1818. 
These facts claim the careful examination of chemists. Hf 
they be verified, they will exhibit the remarkable and hitherto 
unique example of the same base forming a perfect salifiable 
base and a perfect acid simply by uniting with different propor- 
tions of oxygen. ‘This would be a fine confirmation of the theo 
advanced by Cirsted respecting the cause of acidity and alkah- 
nity, of which an account has been given in a late number of the 
Annals of Philosophy.—(See Ann. de Chim. et Phys. viii. 337.) 
9. Cobalt and Nickel.—The most difficult problem, perhaps, 
in practical chemistry is the separation of these two metals from 
each other. A variety of methods have been proposed, all of 
which I have tried, with some additional ones of my own, without 
having yet hit upon one which is not either imperfect, or at 
least liable to some very serious objection. When into a concen- 
trated solution of cobalt in sulphuric or muriatic acid, a solution 
of tartrate of potash is added, a triple salt is formed, consisting 
of tartaric acid, united at once with potash and with oxide of 
cobalt, which crystallizes in large flat rhomboidal prisms, These 
crystals, so far as I have examined them, contain no other metal 
except cobalt ; but this method, though promising at first sight, 
I did not find to answer so well as I expected ; for the tartrate of 
potash undergoes spontaneous decomposition when the solution 
is left to spontaneous evaporation ; and if the evaporation is 
produced by the action of heat, the crystals formed are ill defined, 
and. consequently liable to be impure. 
It was with great pleasure, therefore, that I perused a paper by 
M. Laugier, published in the Annales de Chimie et Physique for 
November, 1818, on the mode of analyzing the ores of cobalt 
and nickel, and on the best method of separating these two 
metals from each other) After trying every known method of 
separating these two metals from each other without succeeding, 
MM. Laugier and Silveira were on the point of abandoning the 
investigation, when it occurred to them to try the effect of a 
concentrated solution of ammonia on the impure oxalate of 
nickel. A solution took place of a fine azure colour. On expos- 
ing this solution to the open air, the ammonia gradually made 
its escape, and at the samg time the oxalate of nickel precipitated 
to the bottom of the vessel; while the whole of the oxalate of 
cobalt remained in solution. Thus it is easy to separate these 
two metals from each other by converting them into oxalates, 
treating the oxalates with ammonia, and leaving the ammoniacal 
solution for some days im an open vessel, I applied this method 
as a test to ascertai the purity of the nickel and the cobalt 
which I had puritied before M. Laugier’s paper came into my 
possession, | had the satisfaction to find that it neither indicated 
the presence of nickel in my cobalt, nor of cobalt in my nickel ; 
therefore, if M. Laugier’s method be a good one, I had succeeded 
ea in accomplishing a complete separation of these two 
metals. 
