A436 On Indigo. 
the mixture each time; the fifth 10 grains pro- 
duced a slight but transient smell; the sixth 
a strong and permanent smell. Hence 250 
were required to saturate 50 of the sulphate. 
The oxide (4 grains) being divided by 9, 
gives .444 for the weight of oxygen in 250 
oxymuriate, or .17 parts of a grain of oxi- 
gen are imparted by each hundred of the 
liquid. 
In the essay above referred to I mentioned 
another method of investigating the value of 
oxymuriate of lime solution. But, owing 
to the then prevailing erroneous notion on 
the proportion of the elements of nitric acid, 
no satisfactory application could be made of 
it. Ll now find that oxymuriate of lime con- 
verts nitrous gas into nitric acid immediately, 
and hence this operation may be used with 
great elegance and precision to shew the real 
quantity of oxymuriatic acid in solutions. 
For example: I took a graduated tube of 
capacity equal to 300 ecrains of water; I 
filled it with pure nitrous gas, and then 
transferred it to a cup of the liquid oxymu- 
riate, valued above by the sulphate of iron. 
After repeated agitation, covering the end 
of the tube carefully with my finger, I soon 
had 100 measures of liquid in the tube: 
then withdrawing it to a cup of water I 
