SOURCES OF ENERGY 171 



iron, manganese, zinc, vanadium, etc. Thermodynamic cal- 

 culations give the equation 



Az= -80822 + 47- IT + 4/ (t/ 298- 16) 



which means that the reaction could occur at the tempera- 

 ture of the lithosphere. 



We may also mention some reactions between acetylene 

 and formaldehyde. One of these in particular gives rise to 

 propargyl alcohol: 



C2H. + CH20^HC=C.CH20H 



and a large number of more complicated products — glycerol, 

 erythritol, hexamethylolbenzene, etc. Tens of different spon- 

 taneously occurring reactions have also been described in 

 which acetylene is condensed with alcohols, ethers, acids, 

 aromatic compounds, etc.^^ 



Acetylene can also react ^vith water or hydrogen sulphide 

 to give heterocyclic compounds. For example, A. Chichi- 

 babin''^ obtained a condensate containing furan by passing 

 steam and acetylene over ai._03 at 400-425° C: 



2C2H0 + H20^C4H40 + Ho 



For this process Az= -56680 + 51T from which it is clear 

 that, from a thermodynamic point of view, it can occur right 

 up to 800° C. 



The corresponding calculation for the reaction by which 

 thiophene is formed (2C2H2 + H2S->C4H4S + Ho) gives Az = 

 - 22760 + 43-3T which suggests that the temperature at which 

 this reaction is thermodynamically possible may be as high 

 as 250° C. 



An interesting possibility for the transformation of the 

 primary hydrocarbons of the lithosphere is provided by the 

 reaction known as the 0x0 synthesis.^* This consists in the 

 simultaneous condensation of olefines ^vith hydrogen and 

 carbon monoxide (which can here be formed by the con- 

 version of methane), e.g. : 



CO + C2H4 -f Ho-^CHg.CHi-CHO 



Many different aldehydes may arise in this way and then 

 give rise to the corresponding alcohols and acids. Acrylic 



