436 Professor Berzelius on [Jijne, 



as double hydrocyanates. But are their elements really com- 

 bined in this manner, or may they be regarded also as cyanurets 

 with water of crystallization*.' 



In compound substances, whose elements may be conceived 

 to be united in several ways, is it indifferent in what manner we 

 imagine the union to take place? Are the products of their 

 decomposition determined solely by the decomposing power? 

 A multitude of circumstances concur in favour of this idea. But 

 if it were correct, a compound body, whose elements are capable 

 of combining at high temperatures, in such a manner as to afford 

 other compounds, endued with a certain tension, at the common 

 atmospheric temperature and pressures, I say this substance 

 must continually decompose in the air, till the tension of its 

 elements is balanced ; and in a vacuum it cannot exist at all. 

 It appears to us that nitrnte of ammonia would decompose in 

 this way in a vacuum, if it were a matter of indifference whether 

 w^e consider it as composed of an atom of ammonia, an atom of 

 nitric acid, and an atom of water, or of an atom of protoxide of 

 azote and two atoms of water, since, in a vacuum, there is no 

 obstacle to prevent these bodies obeying the influence of their 

 tension, as well as the preponderating affinities, any more than 

 at a high temperature, when those two substances are actually 

 ibrmed. It is probable, therefore, that the elements of nitrate 

 of ammonia are combined rather as nitric acid, ammonia, and 

 water, than as protoxide of azote and water. In like manner, 

 when a salt effloresces at the common temperature of the atmo- 

 sphere, we consider the water as existing as such in the salt, 

 but retained by so weak an affinity, that it is overcome by its 

 tension. 



Fulminating gold and silver explode by very slight elevation 

 of temperature, and water results ; but these substances are 

 permanent in a vacuum. The hydrogen and oxygen which they 

 retain with so weak ftn affinity were not, therefore, in the state 

 of water, but combined in another manner, and it is only in the 

 act of explosion that water is formed. But if in these substances, 

 whose composition depends on so weak an affinity, water be not 

 produced, when the effect of its tension is facilitated by a 

 vacuum, we may presume that all bodies which exhale aqueous 

 vapours in a vacuum must contain water ready formed, and that 

 they retain it by a very weak affinity. 



1 put crystals of ferruginous prussiate of potash into a vacuum 

 with sulphuric acid; at the temperature of 35*4° Fahr. they lost 

 all their water of combination : a small piece of a crystal intro- 

 duced into the vacuum of a barometer made it fall O'OOo in. at 

 the temperature of 59" Fahr. I do not give this, however, as a 

 veiy accurate result, from the extreme difficulty of making a 

 solid body rise through the mercury, perfectly free from air 

 adhering mechanically to its surface. The experiment proves, 

 however, that the water of crystallization in this salt is endued 



