462 PRINCIPLES OF CHEMISTRY 



As the above-mentioned relation in composition exists between 

 many chlorine compounds and their corresponding hydrates and as 

 furthermore some (acid) hydrates are obtained from chlorine compounds 

 by the action of water, for instance 



PC1 3 + 3H 2 O = P(HO) 3 + 3HC1 



Phosphorus w - Phosphorous Hydrochloric 



trichloride acid acid ; 



whilst other chlorine compounds (basic) are formed from hydroxides 

 and hydrochloric acid, with the liberation of water, for instance 



XaHO + HC1 = NaCl + H,O ; 



therefore this intimate connection between the hydrates and chlorine 

 compounds is endeavoured to be expressed by calling the latter ch /<>/- 

 anhydrides. In general terms, if the hydrate be basic, then, 



M(HO) + HC1 = MCI + H 2 



hydrate + hydrochloric acid choranhydride + water 



and if the hydrate ROH be acid, then 



RC1 + H,O = R(HO) + HC1 



Choranhydride + water = hydrate -,- hydrochloric acid. 



In this manner a distinct equivalency is remarked between the 

 compounds of chlorine and the so-called hydroxyl radicle (HO), which 

 is also expressed in the analogy existing between chlorine, C1 2 , and 

 hydrogen peroxide, (HO).,. 



As regards the chloranhydrides corresponding with acids and non- 

 metals, they bear but little resemblance to metallic salts. They are 

 nearly all volatile, and have a powerful suffocating smell which irritates 

 the eyes and respiratory organs. They react on water like many 

 anhydrides of the acids, with the evolution of heat and liberation of 

 hydrochloric acid, forming acid hydrates. For this reason they cannot 

 usually be obtained from hydrates that is, acids by the action of 

 hydrochloric acid, as then water would be formed together with them, 

 and water decomposes them, converting them into hydrates. There are 

 many intermediate chlorine compounds between true saline metallic 

 chlorides like sodium chloride and true acid chloranhydrides, just as 

 there are all kinds of transitions between bases and acids ; feeble bases 

 not unfrequeiitly present feeble acid properties. These relations will 

 become gradually clearer as we become acquainted with elements of 

 different character, and for the sake of greater clearness we will not 

 enter into an intimate acquaintance with the saline character of acid 

 .chloranhydrides, and will only remark that compounds of this type are 



