<)N W.\TKK AND ITS COMPOUNDS 111 



\Vt- liave thus considered many aspects and decrees of combination 

 of various substances with water, or instances of the compounds of 

 water, when it and other substances form new homogeneous substances, 

 which in this case will evidently be complex i.e., made up of different 

 substances and although they are homogeneous, yet it must be admitted 

 that in them there exist those component parts which entered into their 

 composition, inasmuch as these parts may be re-obtained from them. It 

 must not be imagined that water really exists in hydrate of lime, any 

 more than that ice or steam exists in water. When we say that water 

 occurs in the composition of a certain hydrate, we only wish to point 

 out that there are chemical transformations in which it is possible to 

 obtain that hydrate by means of water, and other transformations in 

 which this water may be separated out from the hydrate. This is all 

 simply expressed by the words, that water enters into the composition 

 of this hydrate. If a hydrate be formed by feeble bonds, and be decom- 

 posed at even the ordinary temperature, then the water appears as one 

 of the products of dissociation, which in all likelihood is the case in 

 solutions, and forms the fundamental distinction between them and 

 other hydrates in which the water is combined with greater stability 

 and forms a solid substance. 



and 18), and most often form gelatinous masses. Water is held in a considerable quan- 

 tity in solidified glue or boiled albumin. It cannot be expelled from them by pressure ; 

 hence, in this case there has ensued some kind of combination of the substance with water, 

 This water, however, is easily separated by drying ; but not the whole of it, a portion 

 being retained, and this portion belongs, as they say, to the hydrate, although in this 

 CUM' it is very difficult, if possible, to obtain definite compounds. The absence of any 

 distinct boundary lines between solutions, crystallo-hydrates, and ordinary hydrates 

 above referred to, is very clearly seen in such examples. 



