2 56 Mr. Pepys’ Account of a new Eudiometer. 
precipitate solutions of nitrates of mercury, and of silver, and 
acetite of lead, of a dark brown colour, and would be useful 
as chemical reagents. 
Carbonic acid gas, as I have before stated, decomposes solu- 
tions of the acetite of lead, hot, or cold, forming a precipitate 
of carbonate of lead. 
Carbonic acid gas is absorbed by the solution of the green 
sulphate of iron, under the temperature of ioo° Fahrenheit : 
but this is only the action of the water of solution. If the tem- 
perature be near boiling, or above 180° Fahrenheit, the solu- 
tion encreases the volume of the gas without the slightest 
absorption ; after carbonic acid gas has in this way been treated 
with the hot solutions, it is still soluble in water at the common 
temperature, or in aqueous solutions of lime, or alkali. 
Nitrous gas is absorbed by solution of sulphuret of potash, 
with a separation or formation of sulphur. Upon injecting 
the solution the sides of the measure take a milky appearance, 
which on the second injection is washed down, insoluble in the 
liquor. About 80 parts from 100 of gas are absorbed. 
Nitrous gas is also absorbed by nitrate of copper in solution, 
without any peculiar alteration. 
In these experiments, great care must be taken not to en- 
crease the temperature of the gas by the hand. To prevent 
this I use a pair of small circular-mouthed forceps, lined with 
cloth, which firmly grasp the measure, fig. 5 ; and if the expe- 
riments should in any way be delayed, a corresponding mano- 
meter will always be sufficient to correct the error occasioned 
by change of atmospheric temperature and pressure. 
To ascertain the quantity of carbonic acid gas, contained in 
oxygene gas (of a known purity,) after combustion, or de- 
