308 CARBON. 



CARBONIC OXIDE. 



Eg. 17<>> or 14.13; CO; density 972.8 ; |"T"I* 



Priestley is the discoverer of this gas, but its true nature was 

 first pointed out by Cruikshanks, and about the same time by 

 Clement and Desormes. 



Preparation. Carbonic acid is readily deprived of half its 

 oxygen, at a red heat, by a variety of substances, and so reduced 

 to the state of carbonic oxide. The latter gas may therefore be 

 obtained by transmitting carbonic acid over red hot fragments 

 of charcoal contained in an iron or porcelain tube ; or by cal- 

 cining chalk mixed with l-4th of its weight of charcoal in an iron 

 retort. It is likewise prepared by gently heating crystallized 

 oxalic acid with 5 or 6 times its weight of strong oil of vitriol in 

 a glass retort. The latter process affords a mixture of equal 

 volumes of carbonic acid and carbonic oxide, the elements of 

 oxalic acid being carbon and oxygen in the proportion to form 

 these gases, and this acid being incapable of existing except in 

 combination with water or some other base. Now the sulphu- 

 ric acid unites with the water of the cr. oxalic acid, and the acid 

 being set free is instantly decomposed. The gas of all these 

 processes contains much carbonic acid, of which it may be de- 

 prived, by washing it with milk of lime, or by transmitting the 

 gas through a tube filled with the mixture of hydrate of lime and 

 glauber's salt. 



Properties. This gas, as has already been stated, is presumed 

 to contain 2 volumes of carbon, and 1 volume of oxygen, con- 

 densed into 2 volumes so that its combining measure is 2 

 volumes. It is not more soluble in water than atmospheric? air, 

 and has never been liquefied. It is easily kindled and burns 

 with a pale blue flame, like that of sulphur, combining with half 

 its volume of oxygen, and forming carbonic acid, which retains 

 the original volume of the carbonic oxide. This combustion is 

 often witnessed in a coke or charcoal fire. The carbonic acid 

 produced in the lower part of the fire, is converted into carbonic 

 oxide, as it passes up through the red hot embers, and after- 

 wards burns above them with a blue flame, where it meets with 

 air. 



Carbonic oxide is a neutral body, like water, and combines 

 directly, with only a very few substances. It unites with an equal 



