9l< Mr. Connell on eledrolyzing Iodic Acid. 



ihou^^li of course always extremely liappy to find the results 

 obtained by others coincide with my own. In a memoir 

 *' Oil the action of voltaic electricity on alcohol, aether, and 

 aqueous substances," read to the Royal Society of Edinburgh 

 in April 183.5, and printed and distributed in May of that 

 year amongst various individuals and societies in London 

 and elsewhere, several principles of voltaic decomposition 

 were examined, and amongst others the supposed general 

 law, that electrolytes are composed of a like number of atoms 

 of their constituent elements; and I ventured to state my 

 doubts as to the universality of the application of that law; 

 and as one argument in support of these doubts, 1 quoted the 

 very experiment above set forth on fused iodic acid. After 

 showing (printed Mem., p. 24.) by means of the volta-elec- 

 trometer that iodic acid in solution is not directly decom- 

 posed by voltaic agency, but that oxygen is liberated at the 

 positive pole in the same definite proportion as from the elec- 

 tric decomposition of water by the same current, whilst iodine 

 separates at the negative pole in virtue of the secondary ac- 

 tion of nascent hydrogen, 1 observed, p. 26, that it was doubt- 

 ful whether " iodic acid, although it resists decomposition in 

 solution, may not give way in the dry and fused state." After- 

 wards, p. 35, comes the experiment itself on the fused acid 

 in the following words: "1 made some experiments on dty 

 and fused iodic acid, which, from the slight aflinity of its 

 constituents, I thought likely to throw light on the subject* 

 A difficulty, however, presented itself, arising from the cir- 

 cumstance that when completely freed from water its points 

 of fusion and decomposition are extremely near one another. 

 I Ueed it from water by keeping it in a fused state in a tube 

 for a considerable time after a portion of the acid was decom- 

 posed, and until water was no longer evolved. The residue 

 was dry and hard, and was immediately transferred to a long 

 and bent narrow tube ; where platinum wires connected with 

 the two ends of a battery of .50 pairs of 2-inch plates were 

 brought into contact with it, the before-mentioned galvano- 

 meter being also introduced into the circuit. The iodic acid 

 was then heated to fusion by a spirit-lamp, when immediately 

 a considerable, and even permanent deflection of the needle 

 took place. Although it was thus quite manifest that a cur- 

 rent passed, it was impossible for me to say with certainty 

 tliat the acid was decomposed by the voltaic agency, because 

 the heat applied was itself sufficient to cause decomposition 

 and volatilization of iodine on both sides." 



Although I still think that this experiment ought to be 

 viewed with the caution expressed in the above passage, I do 



