404 PRINCIPLES OF CHEMISTRY 



incomplete combustion of dtiarcoal and other carbonaceous fuels. 

 Owing to its faculty of combining with oxygen, carbonic oxide acts as 

 a powerful reducing agent, taking up the oxygen from many compounds 

 at a red heat, and being itself transformed into carbonic anhydride. 

 The reducing action of carbonic oxide, however, is (like that of hydro- 

 gen, Chapter II.) naturally confined to those oxides which easily part 

 with their oxygen as, for instance, copper oxide whilst the oxides 

 of magnesium or potassium are not reduced. Metallic iron itself is 

 capable of reducing carbonic anhydride to carbonic oxide, just as it 

 liberates the hydrogen from water. Copper, which does not decompose 

 water, does not decompose carbonic oxide. If a platinum wire heated 

 to 300, or spongy platinum at the ordinary temperature, be plunged 

 into a mixture of carbonic oxide and oxygen, or of hydrogen and 

 oxygen, the mixture explodes. These reactions are very similar to- 

 those peculiar to hydrogen. The following important distinction, 

 however, exists between them namely : the molecule of hydrogen is 

 composed of H 2 , a group of elements divisible into two like parts, 

 whilst, as the molecule of carbonic oxide, CO, contains unlike atoms of 

 carbon and oxygen, in none of its reactions of combination can it give 

 two molecules of matter containing its elements. This is particularly 

 noticeable in the action of chlorine on hydrogen and on carbonic oxide 

 respectively ; with the former chlorine forms hydrogen chloride, and 

 with the latter it produces the so-called carbonyl chloride, COC1 2 

 that is to say, the molecule of hydrogen, H 2 , under the action of 

 chlorine divides, forming two molecules of hydrochloric acid, whilst the 

 molecule of carbonic oxide enters in its entirety iato the molecule of car- 

 bonyl chloride. This characterises the so-called diatomic or bivalent re- 

 actions of radicles or residues. H is a mohatomic residue or radicle, 

 like K, 01, and others, whilst carbonic oxide, CO, is an indivisible (un- 

 decomposable) bivalent radicle, equivalent to H 2 and hot to H, and 

 therefore combining with X 2 and interchangeable with H 2 . This 

 distinction is evident from the annexed comparison . 



HH, hydrogen. CO, carbonic oxide. 



HC1, hydrochloric acid* COC1 2 , carbonyl chloride. 



HKO, potash. CO(KO) 2 , potassium carbonate. 



HNH 2 , ammonia. CO(NH 2 ) 2 , urea. 



HCH 3 , methane. CO(CH 3 ) 2 , acetone. 



HHO, water. CO(HO) 2 , carbonic acid. 



Such rnonatomic (univalent) residues, X, as H, 01, Na, N0 2 , NH 4> 

 CH 3 , C0 2 H (carboxyl), OH, and others, in accordance with the law 

 of substitution, combine together, forming compounds, XX , and with 



