1815.1 On Iodine, 411 



not afterwards increase in intensity. Potash and mercury destroy 

 this colour on the spot by uniting with the iodine to which it is 

 owing. Its specific gravity at 72*5*' is 1'9206. It boils (as deter- 

 mined by its tension) at 148-6®. By direct experiment, I found it 

 to boil at !48-l°. It is not inflammable; it exhales only purple 

 vapours when thrown upon burning coals. Potassium may be pre- 

 served in it without alteration. Potash produces no immediate 

 alteration on it. The same is the case with nitric and sulphurous 

 acids and chlorine. Concentric sulphuric acid renders it speedily 

 brown. When passed through a red-hot tube, it is decomposed. I 

 obtained an intiammable carbureted gas, very brown hydriodic acid, 

 and a little charcoal. Besides these products, I obtained, by putting 

 a solution of potash into the tube in which I produced the decom- 

 position, a substance in flocks which refused to dissolve in the 

 alkali and in acids. This substance, after being several times 

 washed in cold water, preserved an ethereal odour, but not so strong 

 as that of the liquid ether. In boiling water tlie flocks united 

 together, and melted into a matter, which, after being cooled, re- 

 sembled white wax in appearance. When put upon a burning coal, 

 it gave out without flaming vapour of iodine in greater abundance 

 than the hydriodic ether. It volatilizes, but much more slowly than 

 the ether. 



From these properties I consider the substance of which I have 

 been just speaking as a peculiar ether, formed without doubt by the 

 combination of hydriodic acid with a vegetable matter different 

 from alcohol. 1 have not analyzed hydriodic ether ; but on com- 

 paring it with hydro-chloric ether, which, according to Thenard, is 

 composed of a volume of hydro-chloric gas and half a volume of 

 pure alcoholic vapour, 1 consider its composition as analogous. Ac- 

 cording to this hypothesis, hydriodic ether is con)posed in volume of 



Hydriodic gas 1 



Alcoholic vapour 0*5 



or in weight, of 



Acid 100 



Alcohol 18-55 



and hydro-chloric ether, of 



Acid 100 



Alcohol fM-fi7 



Supposing this composition correct, it is astonishing that hydri- 

 odic ether is not inflanunable, while liydro-chloric etlier possesses 

 that pro[)crtv in a great degree. We cannot suppose that this difler- 

 ence dept'iuis on the proportions in weight of the acids to alcohol. 

 1 rather think that hydriodic ether is not inflammable, because its 

 acid is «lecomposed by oxygen without producing flame, and hence 

 the oxvgcn becomes t(K) small in quantity to support the conil)ustion 

 of the alcohol. It would be easy to verify this conjecture by burning 



