350 Prof. J. W. Mallet on the Atomic Weight of Lithium. 
=7', without however giving the details of the experiments on 
which this number is based. 
On the other hand, Troost, in a paper upon the general history 
of lithia and its salts,* has objected to the method by which my 
determination of the equivalent was made, and has returned to 
a number near that originally given by Berzelius. Troost states 
that chlorid of lithium on being heated in the air loses chlorine 
and takes up oxygen, so that it must give by the method of 
Pelouze an atomic weight for the metal higher than the truth. 
-This fact was distinctly noticed in my former paper, and it was 
stated that the decomposition might be prevented by addition of 
a little pure sal-ammoniac to the chlorid of lithium before heat- 
ing. 
follow from the mechanical loss of the least drop of fluid during 
the effervescence of the carbonate with sulphuric acid or the 
subsequent evaporation of the sulphate of lithia; and, without 
oe the slightest doubt of the manipulative skill of the 
French chemist, we must admit that, in so delicate a process a5 
the determination of an atomic weight, the solution of a carbon- — 
ate and evaporation of the solution—steps which are generally 
*Ann. de Chim, et de Phys., [3], t. x1, p, 108. 
i 
