22 Dr. Kane on the Compounds of Ammonia. 



It would be an exceedingly Interesting point to determine whether the three 

 salts thus found to be generated by the replacement of successive equivalents of 

 water by metallic oxide, and vice versa, possess any simple crystallographic rela- 

 tion to one another. It would be highly important to determine, if the elements 

 thus replacing one another influence the crystalline form of the salt, for if the 

 metallic oxide which replaces water belong to the same isomorphous family, 

 there should exist identity of form amongst those salts, provided the sum of the 

 number of equivalents of water and metallic oxide remains the same. 



If the yellow subnitrate be boiled with much water, in successive portions, it 

 becomes grey, but that alteration is always accompanied by the separation of 

 metallic mercury and the formation of pemitrate. Likewise, if potash be added 

 to the yellow subnitrate it becomes grey, but there is produced a mixture of 

 black oxide and unaltered salt. Thus no positive limit can be found indicating 

 the existence of a blackish or grey sub-protonitrate of really definite composition, 

 and I consider that Donovan and Grouvelle, who had asserted its existence, had 

 been misled by the properties of a mixture of black oxide or of mercury with the 

 subnitrate just described. Indeed Grouvelle, in his paper on the Basic and Acid 

 Nitrates, does not mention this grey subnitrate at all ; but Soubeiran, in dis- 

 cussing the composition of Hannehman's soluble mercury, asserts that it contains 

 the blackish subnitrate described by Grouvelle, of which he gives a formula 

 with numbers, which, by typographical errors, is rendered quite unintelligible, 

 and I have never been able to meet a notice of it elsewhere. It shall be shown, 

 moreover, in the next article, that the nature of Hannehman's mercury is quite 

 different, and hence that ground for supposing a grey sub-protonitrate to exist 

 can no longer hold. 



I therefore conclude that there exists but one basic nitrate of the black oxide 

 of mercury, that which may be obtained as a lemon-yellow powder, or in minute 

 crystals of the same colour, and whose formula is ho.no5 4-2h^o. 



VII. ON THE AMMONIACAL SUBNITRATE OF THE BLACK OXIDE OF MEBCUEY. 



The study of the reaction of water of ammonia on the protonitrate of mer- 

 cury presents great difficulties, in consequence of the facility with which the 

 most important products of it are liable to change, and the consequent admixture 



