EVOLUTION OF GASES FKOM HOMOGENEOUS LIQUIDS. 



291 



from a molecule of formic acid, with production of carbonic oxide, but rather that one 

 molecule of formic acid acts upon another, probably with formation of an unstable 

 anhydride, which in its turn is decomposed into the second anhydride, or carbonic 

 oxide, and water. The reaction between permanganic and oxalic acids, investigated 

 by HARCOURT and ESSON,* affords an example of a case in which a hyperbolic curve 

 represents the course of a chemical change, while the etherification of acids by 

 alcohol, investigated by BERTHELOT,t is also of a similar nature. If the above 

 explanation of the chemical change occurring within the system is correct, the 

 decomposition of formic acid and its etherification by an alcohol would be chemical 

 changes analogous in kind. Thus the reactions can be represented as follows : 



(i.) HCOOH + C,H 6 OH = ^ J O + H 2 O ; 

 (ii.) HCOOH -f HCOOH = + HaO ' 



though the product in the former case is stable in the presence of not too large a 

 quantity of water, while the product of the latter is unstable. The analogy of these 

 two changes is further borne out by the phenomenon of initial acceleration observable 

 in both cases. 



Other series of experiments are given below in a series of Tables, in which are set 

 forth the conditions, the observed values for r, 6 t , and T, the last being compared 

 with those calculated for certain values taken for t, and from the mean number for 

 logC. 



SERIES II. 



205 c.c. of 1 : 4 sulphuric acid, 



10 c.c. of dilute formic acid, containing '308 gram of the acid, which gives 

 15 observations, yielding '12 gram water, or a dilution of '2 per cent. 

 Temperature 68'9 69'0. 



' Phil. Trans.,' 1866, p. 201. 

 t ' Annales do Cbimie' [3], vol. 66, p. 113. 

 2 P 2 



