Dr. Inglis's Extracts from his Prize Essay on Iodine. 443 



but in a letter to Mr. E. Daniell of the 20th of April 1833f, 

 he seems to consider thai compound as an oxide of iodine, and 

 that by an admixture of it with iodic acid, an iodous acid pro- 

 perly so called results; this last is a liquid of an amber co- 

 lour, and is the result of definite proportions only. From my 

 experiments I think that the latter is the correct opinion ; but 

 my iodous acid is solid, whilst both of the former combina- 

 tions are liquid. I most punctually followed the directions 

 given by M. Sementini for the formation of his first iodous 

 acid. I had the salt in excess, and on the application of heat 

 there soon appeared a dense cloud of white vapour, which 

 condensed into white flakes in the receiver. Soon after this 

 the darker iodous vapours appeared, which also condensing, 

 trickled down, and remained liquid in the bottom of the vessel 

 for some time. I poured some of this into a small phial, and 

 soon after it concreted into a solid mass. It fused at a very 

 low temperature, and did not solidify again for a long time. 

 It was not till after standing for several days in a well-stoppered 

 bottle that crystallization took place. By holding the prepa- 

 ration between the eye and the light, the small but regular 

 crystals of iodous acid were seen of a reddish brown colour. 

 When alcohol was added to a portion of it, a solution of an 

 amber colour resulted, and at the same time iodic acid was pre- 

 cipitated. Hence I supposed at first that two compounds were 

 formed in this process, and both solid ; one of a dark brown 

 amber colour, having a great affinity for water, being soluble 

 in it, and in alcohol ; whilst the other, viz. the iodic acid, is 

 insoluble in the latter, and consequently precipitated. Since 

 reading Sementini's last letter, however, I think that the solid 

 iodous acid just described is the result of the union of iodic 

 acid and an oxide of iodine, and is the same as his last iodous 

 acid, only more concentrated. The reason that Sementini's 

 result was different was this ; he did not exclude the air from 

 his, consequently being exceedingly deliquescent, it attracted 

 moisture, and he only saw it in its liquid form, whereas it is 

 evident from the preparation now in Dr. Hope's possession 

 that it is a solid, having somewhat of an acicular crystalline 

 form, exceedingly fusible by heat, and absorbing moisture 

 rapidly. When this acid and alcohol are distilled together, 

 iodous ajther comes over of an amber colour and a peculiar 

 odour. The residue in the retort being still further acted on 

 by heat is decomposed, white vapours escape, and iodine re- 

 mains behind, which crystallizes on cooling. * * * 



Besides the two chlorides already admitted by chemists, 



t [Sig. Sementini's letter was published in Lond. and Ediub. Phil. Mag., 

 vol. ivv p. 392. — Edit.] 



3L2 



