159 
Dr. Angus Smith explained a mode of analysis which he 
has called minimetric. The idea, he said, may perhaps not be 
quite new, hut it is well to give the method a name. It is based 
mainly on the fact that we can retain in the memory with 
great exactness the character of a precipitate of a given 
degree of translucency. For carbonic acid the author finds 
a precipitate of carbonate of baryta caused in baryta by 
*2515 cub. c. of carbonic acid, or nearly three times that 
amount in lime water. If the carbonic acid in air is sought, 
the air is made to act on the baryta until the precipitate is 
obtained. In other words we use the smallest measure of 
air which will produce the precipitate. For this reason 
the name minimetric is adopted. The plan may be used for 
hydrochloric acid, sulphuric and sulphurous acid, sul- 
phuretted hydrogen, &c., and probably has been used 
frequently without bringing it forward as a method for 
accurate use. 
Two modes of using this mode of analysis were described. 
The first was by the use of a finger pump, an elastic ball 
with two valves. When pressed the air was driven out, and 
when expanding the air was drawn through the liquid. The 
air and liquid were then shaken together. This was repeated 
until the precipitate was attained. 
One easy method of finding the precipitate for comparison 
was by shaking half an ounce avoirdupois (14T7 cub. c.) 
with 23 ounces of air in Manchester, or nearly 30 in London, 
or elsewhere, according to residence. 
Experiments made with this apparatus shew it to be 
extremely delicate. The carbonic acid in the air of a room 
can be estimated in a few minutes. 
A table is made of the following kind, but it must be 
