280 Experiments on the Nature of [Oct. 



is ^th of that of the base; and if the water be represented by 1, 

 the acid and oxide will be represented each by 4. On the 

 other hand, 73 - 7 of acid are combined with 908 of oxide; so 

 that 100 parts of acid combine with 12:56 of oxide. We have 

 seen that in the neutral nitrate 100 parts of acid are combined 

 with '205-81 parts of oxide. Now 205'81 x 6 = 1234*86; 

 that is to say, that in the subnitrate at a maximum the nitric 

 acid is combined with six times the quantity of base with which 

 it is combined in the neutral nitrate. 



Intermediate Subnitrate of Lead.- — I precipitated a portion of 

 nitrate of lead by ammonia in excess, but without digesting it 

 in pure ammonia. The precipitate was white; and when the 

 liquid was passed through the filter I perceived that the salt 

 began to dissolve in proportion as the ammoniacal liquor was 

 removed; but it precipitated again in proportion as the drops 

 fell into the liquid that had already passed through the filter. 

 The precipitate, when washed and dried, formed a white pow- 

 der; 10 parts of which exposed in a crucible to a sand heat lost 

 ©•292 of water, and became pale yellow. Being then heated 

 till the whole of the acid was removed, there remained 8 "584 

 of yellow oxide. As such a composition does not accord with 

 the laws of chemical proportions, we must conclude that this 

 precipitate is a mixture of subnitrate at a maximum, and of 

 that in which the acid is combined with twice the quantity of 

 base that exists in the neutral nitrate. 



To obtain the intermediate subnitrate I endeavoured to em- 

 ploy the smallest possible excess of ammonia. I precipitated, by 

 ammonia in a very small excess, a solution of nitrate of lead, 

 and I digested the solution in the excess employed. To decom- 

 pose the subsalt at a maximum which might have been formed, 

 I poured drop by drop a weak solution of nitrate of lead into the 

 mixture, and digested it for half an hour. I then added a little 

 more of the nitrate, and digested again; and I continued this 

 process till the liquor contained no longer any excess of ammo- 

 nia, excepting a portion so small that it could no longer be 

 recognized by the smell, but became sensible by means of a 

 stopper dipped in muriatic acid. I then filtered, and the preci- 

 pitate exhibited the same phenomenon of partially dissolving 

 again, already mentioned. When about the fourth part of tins 

 precipitate was earned away by edulcoration I considered the 

 residue as sufficiently edulcorated, and therefore dried it. 



Th; subsalt thus obtained was analysed in the same manner 

 as the preceding specimens. It yielded pure water, and as- 

 sumed, while still hot, a yellowish colour, but which on cool- 

 in"- was changed into white. Ten parts of it produced 0'35 

 parts of water, and left, when the acid was driven off, 8*298 



