CONSTITUTION OF SALTS. 1G9 



tartaric and citric acids, have all a high atomic weight, which 

 causes them to be fixed, and that the received equivalents of 

 some of them may, therefore, require to be increased, which 

 would afford room for viewing them as bibasic or tribasic. 



Salts usually denominated Subsalts. The preceding classes 

 of salts, and many other bodies also are capable of combining 

 with a certain proportion of water, generally vaguely spoken of 

 as water of crystallization. The compounds of the present 

 class appear to be salts which have assumed a fixed metallic 

 oxide in the place of this water. They may, therefore, be truly 

 neutral in composition, the excess of oxide not standing in the 

 relation of base to the acid. I have elsewhere shewn that 

 crystallized nitrate of copper, nitrate of water, (acid of sp. gr. 

 1.42), and subnitrate of copper may be represented by the 

 formula?, CuO, NO 5 + 3HO; HO, NO 5 + 3HO; and HO, 

 NO 5 + 3CuO, and have distinguished as constitutional, the 

 three atoms of water which exist in these and all the mag- 

 nesian nitrates, and which are replaced by three atoms of oxide 

 of copper in the subnitrate of copper, which is, therefore, a 

 nitrate of water with constitutional (not basic) oxide of copper, 

 a view which is expressed by the arrangement of the symbols 

 in its formula. Water, oxide of copper and oxide of lead 

 appear to be the bodies most disposed to attach themselves 

 to salts in this manner. The strong alkalies, potash and 

 soda are never found in such a relation, or discharging any 

 other function than that of base to the acid of the salt. 

 These views of subsalts, in which their constitutional neutra- 

 lity is preserved, have been adopted by Liebig and Dumas, 

 and extended to organic compounds. Many neutral organic 

 bodies appear to be capable of combining with metallic oxides 

 particularly with oxide of lead, such as sugar, amidine, dextrine, 

 orcine, and they generally combine with several atoms of the 

 oxide ; the neutral bodies mentioned being fixed and probably 

 possessing a high atomic weight. Thus in the compound of 

 orcirie and oxide of lead, C 18 H 8 O 3 + 5Pb O, the orcine must 

 be present in the proportion of one atom, as the numbers of 

 its constituent atoms have no common divisor ; and the 

 orcine, therefore, is combined with five atoms of constitutional 

 oxide of lead, which actually replace five atoms of constitutional 

 water which orcine otherwise contains. 



Constitutional water is sometimes replaced by a salt* which 



