386 Scientific Notices— Chemistry. [Nov. 



4. lodous Acid. 



II Sig. Sementini, of Naples, has published an account of a 

 combination of iodine and oxygen, containing less of the latter 

 principle than iodic acid. It is obtained in the following man- 

 ner : — Equal parts of chlorate of potash and iodine are to be 

 triturated together in a glass or porcelain mortar, until they 

 form a very fine pulverulent yellow mass, in which the metallic 

 aspect of the iodine has entirely disappeared. If there be excess 

 of iodine, the mixture will have a lead colour. This mixture is 

 to be put into a retort, the neck being preserved clean, and a 

 receiver is to be attached with a tube passing to the pneumatic 

 trough. Heat is then to be applied, and for this purpose a spirit 

 lamp will be found sufficient ; at first a few violet vapours rise, 

 but as soon as the chlorate begins to lose oxygen, dense yellow 

 fumes will appear, which will be condensed in the neck of the 

 retort into a yellow liquid, and run in drops into the receiver ; 

 oxygen gas will at the same time come over. When the vapour 

 ceases to rise, the process is finished, and the iodous acid 

 obtained will have the following properties : — 



Its colour is yellow, its taste acid and astringent, and leaving 

 a burning sensation on the tongue. It is of an oily consistency, 

 and flows with difficulty. It is heavier than water, sinking in it. 

 It has a particular odour, disagreeable, and something resembling 

 that of euchlorine. It permanently reddens vegetable blues, 

 but does not destroy them as chloric acid does. It is very solu- 

 ble in water and alcohol, producing amber-coloured solutions. 

 It evaporates slowly, and entirely in the air. At 112° Fahr. it 

 volatilizes rapidly, forming the dense vapour before mentioned. 

 It is decomposed by sulphur, disengaging a little heat, and libe- 

 rating violet vapours. Carbon has no action on it at any tem- 

 perature. Solution of sulphurous acid decomposes it as well as 

 iodic acid, precipitating the iodine as a brown powder. It is 

 characterized by the manner in which potassium and phosphorus 

 act on it : the instant they touch it they inflame ; the potassium 

 producing a white flame and dense vapours, but little or no libe- 

 ration of iodine, and the phosphorus, with a noise as of ebulli- 

 tion, violent vapours appearing at the same time. 



The odorous nature of this acid, its volatility, colour, and its 

 power of inflaming phosphorus by mere contact, show that some 

 of the principal characters of iodine are retained, and that it is 

 oxygenated, therefore, in a minor degree, and deserves the name 

 of iodous acid. 



Its composition has not been experimentally ascertained. 

 M. Sementini endeavoured to analyze it by putting 100 grains 

 into the end of a long sealed tube, and then dropping a small 

 piece of phosphorus in, iodine was disengaged, and condensed 

 in. the upper part of the tube, and this was found to amount to 

 45 grains ; but this can furnish only very uncertain results. 



