xii THE HALOGENS 241 



described the discovery of a new member of the group of 

 halogens : 



"I have observed several times that, on treating with 

 chlorine-water the extract of the iodine-containing ashes of 

 seaweed, after having added a solution of starch, there 

 appears not only a blue zone due to iodine, but above this 

 a zone of bright yellow." 



" This orange-yellow colour was shown also when I 

 treated the mother-liquor of sea-salt in the same way. . . . 

 The appearance of this hue was accompanied by a strong, 

 peculiar smell." 



" The saline mother-liquor, treated thus with chlorine, 

 loses its colour and its characteristic smell by exposure 

 to air during one or two days " (loc. cit. p. 337). 



" The yellow saline liquor, submitted to distillation, 

 liberated, during the first moments of boiling, thick, red 

 vapours which condensed on cooling to a liquid, which 

 retained most of the properties of the coloured liquor ; but 

 these properties were much more pronounced." 



" In order to obtain this substance in a pure state, . . . 

 I passed the red vapours over calcium chloride. They 

 condensed in a small receiver, in volatile, deep-red drops, 

 filling the little vessel in which they were contained with 

 vapours comparable in colour with nitrous vapour " (loc. cit. 

 PP- 33 



The aqueous liquid was decolorised by the action of 

 alkalis, and by reducing agents such as zinc and sulphuric 

 acid, sulphurous acid, hydrogen sulphide, and ammonia, 

 but the colour could be restored by the addition of more 

 chlorine. The properties of the substance suggested that it 

 might be a new chloride of iodine, but it gave none of the 

 usual tests for this element, and could not be decomposed, 

 even by the electric arc. It appeared, indeed, to be an 

 element, closely resembling chlorine and iodine, forming 

 a series of analogous compounds, but clearly to be dis- 

 tinguished from these elements both in its physical properties 

 and in its chemical actions. 



