242 HYDROGENATED COMPOUNDS OF NITROGEN. 



Weight of water obtaiaed. "^T^SSS* 



0-880 grms. 

 0-819 

 1-004 

 1-110 

 1-006 



+ 91-1 Cal. 

 + 90-7 

 + 91-7 ,, 

 + 91-4 

 + 91-4 , 



Mean + 91-3 



The heat of combustion of ammonia in solution will thus be 

 + 82*5. 



6. It is easy to deduce from this the heat of formation of 

 ammonia by its elements, without resting on any other basis 

 than the heat of formation of water. This being admitted, 

 according to the following data 



H 2 + = H 2 liquid gives off + 34'5, 

 we deduce 



N + H 3 = NH 3 gas liberates + 103*5 - 91*3 = + 12*2. 



The author found l that the solution of the ammoniacal gas 

 in a large quantity of water gives off + 8*82. Thus 



N 4. H 3 -f water = NH 3 dilute gives off 4- 21 Cal. 



The value obtained with the hypobromite (-f 22*8) differs little 

 from this ; but it is necessarily less exact on account of the 

 complication of the reactions. 



The author therefore adopts the respective values of +21 

 and + 12-2 for the formation of ammonia in solution and in the 

 gaseous form. 



Between the result + 12*2 and the figures +26*7 previously 

 adopted, there is a discrepancy of 14*5 ; this is the greatest 

 experimental error that has up to the present been committed 

 in thermo-chemistry. Its source has been shown, and it has 

 been rectified accordingly. 



7. Some months after the first publication of the results of 

 the author's researches, Thomsen repeated the experiments, and 

 he obtained for the heat of combustion of ammonia + 90 '65, a 

 value agreeing with +91*3 within the limits of error allowed 

 in experiments of this order. This is an important confir- 

 mation of the experiments. The heat of formation of ammonia 

 seems, therefore, to be definitely fixed at + 12*2, or very 

 near this. 



1 " Annales de Chimie et de Physique," 5 e serie, torn. iv. p. 526. 



