366 CARBONIC ACID. 



(b.) A coated glass or porcelain tube filled with charcoal that has 

 been heated till it has ceased to yield any gas, is placed across a fur- 

 nace and ignited ; one end being connected with a gazometer to af- 

 ford oxygen gas or common air ; the other with a pneumatic appar- 

 atus to receive the gas ; by adding another gazometer, the gas may 

 be made to pass repeatedly back and forward. 



(c.) Diamond, charcoal, plumbago and anthracite, or any varieties 

 of carbon may be treated in the same manner, as was done by Messrs. 

 Allen and Pepys, in their celebrated experiments ; they used a pla- 

 tinum tube to contain the diamond and other forms of carbon, and 

 their gazometers were placed over mercury. 



(d.) Burn charcoal in a bottle or jar of oxygen gas ; if a piece of 

 well charred bark be used, the combustion is attended with brilliant 

 scintillations ; otherwise with only a bright glow. 



(e.) Burn any kind of wood, or a taper, in a bottle of common 

 air, or of oxygen gas, and carbonic acid will be formed, as may be 

 evinced by the test of lime water, which produces a milky precipi- 

 tate. 



(f.) Diamond is easily made to burn under the compound blow- 

 pipe,* and wastes entirely away. If the combustion be stopped in 

 its progress, the surface of the diamond will be found, not carbonized, 

 but indented and dull, as if it had been corroded and then washed. 

 In my experiments it had the appearance of superficial fusion. 



(g.) An elegant apparatus for the combustion of diamond, is fig- 

 ured by Mr. Brande, in his elements, and copied by Dr. Henry,f by 

 which the diamond may be burned, and the products collected. By 

 combustion, it is rapidly diminished, and carbonic acid is abundantly 

 precipitated by admitting lime water. 



(h.) According to the experiments of different eminent chem- 

 ists, J 28 or 29 grains of any pure carbon, require 71 or 72 of oxy- 

 gen and give 100 carbonic acid; 201 cubic inches of oxygen by 

 bulk, require 28 or 29 grains of charcoal. Mr. Dalton assumes the 

 composition of carbonic acid to be, in round numbers, 28 carbon to 



that diamond is carbon, was unavoidable. In 1785, Guyton Morveau, found that 

 the diamond, when dropped into melted nitre, burns without any residuum, and in a 

 manner analogous to charcoal. Dr. Tennant also burnt the diamond in nitre, and 

 found that carbonic acid gas was the only product. (Phil. Trans. 1797.) Guyton 

 Morveau observed, that the diamond burns at three different temperatures, and al- 

 though some of his conclusions were erroneous, for instance, that the diamond can 

 be converted into a substance resembling charcoal, and that charcoal is an oxide of 

 carbon, still he fully established the fact that diamond is by combustion, converted 

 into carbonic acid. 



* See Am. Jour. Vol. VI, p. 349. t Vol. I, p. 342, 10th Ed. 



t Carbon, 28.60; oxygen, 71.40=100. Carbon, 27.376; oxygen, 72.624=100. 

 Allen and Pepys, Clement and Desormes, Wollaston, Gay-Lussac, and Berzelius. 

 See Henry, 10th Ed. Vol. I, p. 344. 



4 The precise proportions appear to be 72.72 of oxygen, and 27.27 of carbon, 

 which corresponds with 2 proportions of oxygen and of 1 carbon. Murray. 



