AMMONIUM BICHROMATE. 415 



But this figure is only applicable to low densities of charge. 

 For high densities the chlorine is liquefied and occupies 227 c.c. 

 The volume of the permanent gases is in this way diminished 

 by one-fourth. 



The permanent pressure then becomes - -^ - , which makes, 



n Q'534 



for n = 1, 631 kgm. per square centimetre. 



At the theoretical temperature of decomposition, the water 

 and the chlorine being gaseous, the pressure becomes 



893 atm.l 



. 6Q()4 



- = _ - or - _, 

 n n n 



figures which are not very remote from the maximum effects of 

 which ammonium nitrate is capable. 



The decomposition which served as base for the foregoing 

 calculations is not exclusive, a small quantity of perchlorate 

 being decomposed at the same time with formation of hydro- 

 chloric acid ; now 



2C10 4 NH 3 = 2HC1 + 3H 2 + N + 5 liberates + 30-8 Gal, 

 producing 1004 litres (l -f ^zr) of gas. But this reaction is 



\ Z7o/ 



accessory. 



8. AMMONIUM BICHROMATE: C&) 6 (NHJaO. 



1. We shall take this salt as a type of the ammoniacal salts 

 formed by the metallic oxacides. 



Its equivalent is 126*4. 



2. Composition 



N ............... =1 111 



Cr ............... = 415 



H ............... = 32 



............... = 442 



1000 



3. The heat of formation from the elements cannot be 

 calculated, the heat of oxidation of chromium being unknown. 

 But the decomposition of the salt not producing any oxide 

 lower than the chromium sesquioxide, it is sufficient to 

 calculate its formation from this oxide and the pre-existing 

 water contained in salts of ammonia. 



The author has thus found : l 



Cr 2 3 (precip.)-h 4 + H 8 + N 2 = Cr 2 O 3 + 2NH 3 + H 2 (solid) 



+ 79-0 Cal. 



1 " Comptes rendus des stances de 1'Acade'mie des Sciences," torn. xcvi. 

 pp. 399 and 536. 



