Mr. Pepys’ Account of a new Eudiometer. 255 
when we recollect that the carbonic acid gas is soluble in the 
water of solution, at the common temperature of all these 
compounds. 
Nitrous gas, and carbonic acid gas, may be separated by 
means of the hot solution of the green sulphate of iron. To 
effect this, heat a solution on a glass capsule over a spirit lamp 
until ebullition. Having filled the measure with the compound 
gas, charge the elastic bottle with the hot solution, and unite 
them. The nitrous gas in two or three injections will be 
absorbed, changing the colour of the solution, while the car- 
bonic acid gas will be a little rarefied, but no absorption of 
it will take place. 
Previous to these experiments on the compound gases, I had 
tried several on the carbonic acid, sulphurated hydrogene, and 
nitrous gases in their unmixed states. One hundred parts of 
pure alcohol at the common temperature will absorb 70 parts 
in volume of carbonic acid, and the same quantity of sulphur- 
ated hydrogene. Alcohol impregnated with the latter, pre- 
cipitates the solutions of the nitrates of lead, silver, and mer- 
cury, of a dark-brown colour. Nitric acid of the specific gravity 
1.4, and also of 1.25, absorbs carbonic acid gas, without any 
apparent change in the nitric acid. Sulphurated hydrogene 
gas is also absorbed by nitric acid, which occasions a slight 
milky cloud or precipitate therein. 
The solutions of nitrates of barytes, strontian, and lime, ab- 
sorb carbonic acid gas equal to half their volume, without any 
apparent alteration. 
Solutions of nitrates of barytes, strontian, and lime, also ab- 
sorb sulphurated hydrogene gas, equal to of their volume, 
with a slight change of colour ; the solutions thus impregnated, 
L 1 2 
