372 Di'. 0(11 in g on Ortho- and Meta-silicates. 



phosphate of silver had chanced to be of a white, instead of a 

 yellow colour. 



The relations of nitrates and phosphates to cai'bonates and 

 silicates rcspectivelj^ are very interesting. Ordinary niti-ates and 

 carbonates correspond to metaphosphates and metasilicates ; but, 

 as we shall presently see, representatives of orthophosphates and 

 orthosilicatcs are not entirely wanting. 



The analogy of composition between nitrates and metaphos- 

 phates is obvious, the analogy of properties is doubtless slight ; 

 but, admitting them to be comparable salts, we should scai'cely 

 expect to find any striking resemblance between them, seeing 

 that nitrogen is so widely separated from the other members of 

 its family, precisely as are fluorine, oxygen, and carbon from 

 the other members of their respective families : — 



Fluorine Chlorine, bromine, iodine. 



Oxygen Sulphur, selenium, tellurium. 



Nitrogen Phosphorus, arsenic, antimony, bismuth. 



Carbon Silicon, titanium, &c. 



Now, in accordance with the general law, that binary hydrides 

 yield ternary or ox-acids containing the same number of hydrogen 

 atoms, we should expect that ammonia, or the ter-hydride of 

 nitrogen, so analogous in most of its characters to phosphamine, 

 P IP, would, like that body, yield terhydric acids and terbasic 

 salts. Such, however, is not usually admitted to be the case; 

 but, by regarding our ordinary nitrates as analogues of the meta- 

 phosphates, we are naturally led to inquire whether the habi- 

 tudes of the metaphosphates, M PO^, in their relations to the 

 orthojjhosphates, M^ PO'', may not be paralleled to some slight 

 extent in the nitrates, MNO^, — whether they may not have a latent 

 tendency to take up an atom of base, and thereby become what 

 we may term orthonitrates, ^NI^NO"*, that is, quadroxidized com- 

 pounds of metallicized ammonias. We are acquainted with a 

 great variety of basic nitrates, and among them some may be 

 found which have a composition represented by the general for- 

 mula (M^ . i\IN03) or M-"' NO*. But we know that basic salts 

 comprise salts formed under very various circumstances, modelled 

 upon different types, and having little in common with one 

 another, beyond the fact of their super-basicity. Unless there- 

 fore the salts having the general formula ]\1^ NO^, have certain 

 special jiroperties, distinguishing them from the ordinary run of 

 basic salts, very little stress can be laid upon the accident of 

 their comjiosition. But we find, in reality, that basic nitrates of 

 the above formula are rem ;irk able from the circumstances attend- 

 ing their foi'inatioii, from their crystalline character, and from 

 their solubility in water. Thus — 



