COMPOUNDS OF CARBON WITH OXYGEN AND NITROGEN 39$ 



interchanir<';il>lr with H 2 . This distinction is evident from the annexed 

 comparison : 



HH, hydrogen. CO, carbonic oxide. 



HC1, hydrochloric acid. COC1 V , carbonyl chloride. 



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



HXH._>, ammonia. CO(NH 2 ) 2 , urea. 



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



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



Such monatomic (univalent) residues, X, like H, Cl, Na, NO 2 , NH 4 , 

 CH 3 , CO._,H (carboxyl), OH, and others, in accordance with the law 

 of substitution, combine together, forming compounds, XX' ; with 

 oxygen, or in general with diatomic (bivalent) residues, Y for instance, 

 with O, CO, CH 2 , S, Ca, <fcc. compounds XX'Y ; but diatomic- 

 residues, Y, sometimes capable of existing separately, combine together, 

 YY' and with X 2 or XX', as we see from the transition of CO into 

 C0 2 and COC1 2 . This combining faculty of carbonic oxide appears in 

 many of its reactions. Thus it is very easily absorbed by cuprous 

 chloride, CuCl, dissolved in fuming hydrochloric acid, forming a 

 crystalline compound, COCu 2 Cl 2 ,2H 2 O, decomposable by water ; it 

 combines directly with potassium (at 90), forming (KCO) K 31 with 

 platinum dichloride, PtCl 2 , with chlorine, C1 2 , &c. 



But the compounds of carbonic oxide with the alkalis are still more 

 remarkable for instance, with potassium or barium hydroxides, &c. 

 although it is not directly absorbed by them, as it has no acid 

 properties. Berthelot (1861) showed that potash in the presence of 

 water is capable of absorbing carbonic oxide, but the absorption 

 takes place slowly, little by little, and it is only after being heated 

 for many hours that the whole of the carbonic oxide is absorbed by 

 the potash. The salt, CHK0 2 , is obtained by this absorption ; it cor- 

 responds with an acid found in nature, namely, the simplest organic 

 carboxylic acid, formic acid, CH 2 O 2 . It can be extracted from the 

 potassium salt by means of distillation with dilute sulphuric acid, 

 just as nitric acid is prepared from sodium nitrate. The same acid 

 is found in ants, in nettles (when the points of the nettles enter 



31 The molecule of metallic potassium (Scott, 1887), like that of mercury, contains one 

 atom, and it is probably in virtue of this that the molecules CO and K combine together. 

 But as in the majority of cases potassium acts as a univalent radicle, the polymeride 

 K. 2 C.>O 3 is formed, and probably K 10 C 10 O 10 , because products containing CIQ are formed 

 by the action of hydrochloric acid. The black mass formed by the combination of 

 carbonic oxide with potassium explodes with great ease, and oxidises in the air. Although 

 Brodie and Lerch have greatly extended our knowledge of this compound, much still 

 remains unexplained. 



