on the Nature of certain Bodies. 75 
difference between the amalgam of ammonium, and mercury, 
in which the quantity of new matter is not more than -j-L—, 
or that between the metals and their sub-oxides, some of 
which contain less than jL of oxygene, will not be disposed 
to question the principle, that minute differences in chemical 
composition may produce great differences in external and 
physical characters. 
6 . Experiments on the Decomposition, and Composition of the 
Boracic Acid. 
In the last Bakerian Lecture,* I have given an account of 
an experiment in which boracic acid appeared to be decom- 
posed by Voltaic electricity, a dark coloured inflammable 
substance separating from it on the negative surface. 
In the course of the spring and summer, I made many at- 
tempts to collect quantities of this substance for minute exa- 
mination. When boracic acid, moistened with water, was 
exposed between two surfaces of platina, acted on by the full 
power of the battery of five hundred, an olive-brown matter 
immediately began to form on the negative surface, which 
gradually increased in thickness, and at last appeared almost 
black. It was permanent in water, but soluble with efferves- 
cence in warm nitrous acid. When heated to redness upon 
the platina it burnt slowly, and gave off white fumes, which 
slightly reddened moistened litmus paper, and it left a black 
mass, which, when examined by the magnifier, appeared vitre- 
ous at the surface, and evidently contained a fixed acid. 
These circumstances seemed distinctly to shew the decom- 
position, and recomposition of the boracic acid; but as the 
* Page 43. 
