11.52 
MR. G. F. RODWELL ON THE EFFECTS OF HEAT ON CERTAIN 
be powdered, the powder presents the same grey-white colour as the original precipitate. 
Soubeiran asserts that cuprous iodide fuses to a brown mass, which yields a green 
powder, and I imagine from this that he did not entirely wash out all traces of ferrous 
and ferric sulphate from the precipate. In thin laminae it is translucent, transmitting 
a greenish light. It fuses at 601° C. according to the determinations of Mr. Thomas 
Oarnelley. When heated in the air it begins to give off iodine soon after the tempe¬ 
rature has passed 230° C., but it gives it off most copiously when fused in the air. 
Oxide of copper is left. 
When heated in a current of dry carbonic anhydride the iodide gives off a small 
amount of iodine, and afterwards remains in tranquil fusion without undergoing 
decomposition. At a bright red heat it slowly volatilises, the sublimate condensing 
immediately above the molten mass which is producing it. When heated in a current 
of dry oxygen, iodine is freely evolved, and oxide of copper ultimately remains in the 
form of a fine crystalline powder. 
A quantity of iodide weighing 9'0080 grms. was heated for many hours in an air- 
bath to a temperature of 190° C. It lost *4551 per cent. On raising the tempera¬ 
ture and maintaining it between 200° and 300° C. for several hours the loss increased 
to 3*3303. It was then ignited over a one-jet Bunsen burner for 16 minutes, 
the cover being retained on the crucible. The total loss amounted to 4*6514. The 
crucible was now strongly heated over a four-jet Bunsen burner; the mass of course 
freely fused, and evolved iodine although the crucible was covered. After heating for 
10 minutes the loss due to this heating was 1*3987, and the total loss was equal to 
6*0501 per cent. A further ignition of five minutes only raised the total loss to 
6*3277. The ignition was then continued with the cover of the crucible removed. 
Iodine was freely evolved. After more than an hour’s ignition no more iodine was 
evolved, and the weight became constant. The loss amounted to 40*4639 per cent, of 
the whole, leaving in the crucible 3*6450 grms. of cupric oxide in minute crystals. 
The calculated weight of the residue, on the supposition that all the Cu 3 I 3 is converted 
into CuO, is 3*7590 grms. Hence there can be no doubt that the iodine is completely 
expelled and replaced by oxygen. Subsequent testing of the residue failed to reveal 
the presence of any iodine. 
16*0130 grms. of the iodide only lost 0*6106 per cent, by heating for about 15 hours 
to a temperature of 230° C. 2*8050 grms. heated for some time to 190° C. lost *2495 
per cent.; at 231° C. it lost 1*2830; on raising the temperature to 260° C. for some 
hours the loss increased to 17*7540. Ignition for 20 minutes over a one-jet Bunsen 
burner (the cover being kept on the crucible) raised the loss to 25*7932. The cover 
was then removed, and after strong ignition for more than an hour no more iodine 
was evolved, and 1*1703 grm. of oxide of copper remained in the crucible. The 
calculated amount is 1*1755. 
The loss of weight on ignition is equal to the difference between the atomic weight 
of iodine and of oxygen, for the change is expressed by C%I 3 +0 3 =2Cu0-f I 3 . Hence 
