30 Proceedings of Royal Society of Edinburgh. [sess. 
It was then determined to ascertain whether ferric oxide in 
presence of oxygen would oxidise sulphuretted hydrogen solution. 
Ignited ferric oxide, also some red haematite, were placed in a 
Lunge nitrometer with a solution of sulphuretted hydrogen, and 
mixed with this was some oxygen, but no action took place ; the 
gas did not diminish in volume. When ferric oxide is replaced 
by ferric hydroxide, oxidation takes place with great rapidity. 
It follows, then, that sulphuretted hydrogen is not oxidised to 
sulphuric acid simply by the oxygen of the air, and ferric oxide is 
not acted upon by sulphuretted hydrogen so as to produce ferrous 
sulphide and free sulphur, according to Dr Murray and Mr Irvine’s 
equation : — 
(4) Fe 2 0 3 + 3H 2 S = 2FeS + S + 3H,0* 
For such action to take place it is necessary that the ferric com- 
pound should be the hydroxide, such as is used in the purification 
of coal-gas. 
The thermo-chemical equations worked out for the chemical 
changes which take place between the organic matter and the 
mineral salts in mud, show that, at each stage, there is heat evolu- 
tion : — 
The fermentation of cellulose. — The composition of cellulose, and 
also of starch, is a:(C 6 H 10 O 5 ) ; where x is a whole number, probably 
not less than ten. The first change in all such carbohydrates is 
hydrolysis, or the simple addition of the elements of water to 
the molecule or fraction of the molecule represented by 
C 6 H 10 O 5 ; accordingly we have cellulose and water represented by 
c 0 h 10 o 5 + h 2 o. 
Heat of Formation. 
(Berthelot’s Tables in Salet’s Agenda du Chimiste.) 
Heat Units. 
C (diamond) + 0 2 = C0 2 (gas) + 94’3 f 
C (diamond) + 0 2 = C0 2 (dissolved) +99-6 
* The above action can take place only at a high temperature, as, for 
instance, in the Claus kiln, but in the working of this kiln, by the judicious 
admixture of air, the formation of FeS is prevented, the Fe 2 0 3 remains 
unchanged and sulphur is separated. 
f C (amorphous) yields +97 '6 units. 
