INCOMPATIBILITIES OF IODINE AND IODIDE OF POTASSIUM. 67 
among the metals, antimony, copper, lead, mercury, bismuth, sil- 
ver, and gold, combine with iodine, and give birth to compounds 
in which its dynamic action is more or less modified. To the above 
may be added, with the same remark, those with which soluble 
iodides are formed, as iron, manganese, and zinc. Among the in- 
compatible chemical compounds are ammonia, with which it pro- 
duces an explosive compound, and sulphohydric and cyanhydric 
acids, which it decomposes, transforming itself into iodhydric 
acid. Nitric acid oxidizes it. Moist sulphurous and arsenious 
acids, brought into contact with it, become super-oxygenated while 
it is hydrogenised. It gives various results with the metallic 
oxides, properly so called, but usually produces insoluble iodides. 
From sulphates it liberates the sulphur and siezes the metal. 
From the salts of antimony, copper, mercury, silver, &c, it forms 
insoluble iodides with their metals. Almost all organized substan- 
ces may be considered incompatible, in consequence of the tenden- 
cy which this body has to sieze the hydrogen, giving rise to va- 
rious compounds, of which iodhydric acid almost always forms 
part. Yet the iodine taken in this form into the economy retains 
in a great measure its dynamic action. Thus for the purpose of 
moderating the irritating action of iodine, or the salts of mor- 
phia, belladonna, &c, are often added ; and experience teaches us, 
that in spite of the incompatibility of the alkaloids with iodine, 
the action of this substance is obtained. Still there can be no 
doubt that its activity is diminished from this cause. 
The metals already named also produce insoluble iodides with 
iodide of potassium. If the iodine is in small quantities, potash 
is produced, and a double iodide if in large. The salts of these 
metals give rise to a double decomposition, producing a soluble 
salt of potassa, and an insoluble iodide. Organic incompatibilities 
are much less frequent than in the case of iodine, as the avidity 
which this substance has for combination is already satisfied with 
the potassa. Apart from the acids, as the citric, acetic, and tartar- 
ic, there are not any organic substances manifestly incompatible 
with the iodide of potassium. 
By reason of the incompatibility of silver with iodine and 
iodide of potassium, pills should never be silvered, nor should me- 
dicine be administered by means of silver spoons. 
