52 REPORT—1874. 
when metallic iron in the form of sponge was similarly treated, it was transformed 
into porous oxide. In neither case was any deposited carbon produced. 
In the present trials, the proportions of cyanogen and carbonic acid first employed 
were one volume of the former and six of the latter, because in such a mixture the 
relation of oxygen to carbon is the same as that subsisting in equal volumes of the 
two gaseous oxides of carbon which, as just stated, were incapable of reducing iron 
to the metallic state. 
Experiment 1.—Such a mixture (1 of Cy+6 of CO,) was passed through the 
tube containing no oxide of iron at a temperature of 814° C., which was gradually 
lowered. The gas as it escaped was so nearly absorbed by potash as to be 
accounted for by a trace of atmospheric air remaining in the apparatus; for the 
slight trace of unabsorbed gas burnt with the characteristic blue flame of carbonic 
oxide. It was therefore inferred that heat alone effected no change in this mix- 
ture of the two gases. 
Experiment 2.—A similar mixture (1 Cy+6 CO,) was passed over pure peroxide 
of iron at a temperature varying from 685° to711° C. Large quantities of nitrogen 
and carbonic oxide were given off during the whole of the experiment, accompanied 
by cyanogen and carbonic acid escaping unchanged. 
The original weight of the ferric oxide was.......... 16465 gramme. 
After an exposure of 13 minutes, during which 1:28 litre 
of the mixed gases had passed through the tube, it 
SWVC Ue GC pete ast cates stndelinib ka. o1sce Sint oyate 6 7s.0ce lee ofa lagapnes 15295 A 
After a lapse of 2% hours, and after 8°5 litres of the gases 
had passed yatiweiphedss.t. vif siewlet Stee ilelekles onl 1:5855 F 
_ On analysis the substance exposed was found to consist, for every 100 parts of 
iron, of— 
Tron in the metallic state ........ csc cece eee . 56:3 
Dryoniasian OXIA $., cecapnaieraisraleleorsa dein als yradebatye .. 43:7 
Oxygen...... Rex wisi Viel ferro ieih ad ite eto tat 9:1 
Cainbonyadieediirers:tstsyeaiisiste crabeloseieearcias <ictemiarerals 28:5 
In this case 799 per cent. of the original oxygen has been removed. 
Experiment 3.—Spongy iron was now exposed to the same mixture (1 Cy+6 CO,) 
at a temperature of 712° to 726°C, The issuing gases contained carbonic oxide and 
nitrogen, as in the previous experiment. 
The original iron weighed............ SR CMIRR ER. ORE 1:314 gramme. 
In 56 min. 6:7 litres of the mixed gases had passed through 
the tube, the iron was found to weigh.............. 1:596 + 
In 2 hrs. 20 min. 14 litres had been used, and the pro- 
UGH EWCTE HEM! Lik cise. litsmyaueeiers voltetelerels winllairiele we eeaters 1600) so; 
For every 100 parts of iron it consisted of— 
Tron in the metallic state ........sseeeereeees 58'7 
Tron as an oxide ..... afar’ Getepher bacwediee 41°3 
Oxygen..... cia Sines ook xe stwrathe sae bats vier totetet 96 
Warbon. berr{« Fie 2earste biviosy ow dae er Gee Me sak el 
There is such a similarity in the composition of the products in experiments 2 
and 3 as to render it probable that at the same temperature, when about 57 or 58 
per cent. of the iron exists as metal, and the remainder consists of 8 equivalents of 
iron united to 6 equivalents of oxygen, further action ceases, whether iron or its 
peroxide be the substance employed. 
The superior power of cyanogen over carbonic oxide to keep in check the oxi- 
dizing tendency of carbonic acid haying been demonstrated, the latter was now 
increased in quantity. 
Experiment 4.—Pure peroxide of iron was exposed to a current of 1 yolume 
ovanegen and 15 volumes of carbonic acid, the temperature varying from 801° to 
The issuing gases again contained, as before, nitrogen and carbonic oxide. 
