498 Intelligence and Miscellaneous Articles. 
‘water, it soon becomes of a deep red colour, and deposits plombie 
acid; acids, added to the plombates, occasion the precipitation of 
plombic acid. 
All plombates are obtained by calcining in the air a mixture of 
metallic lead and protoxide of lead. ‘Thus, then, minium or red lead 
is one of the series of plombates ; it is a plombate of protoxide of 
lead. It is well known that when a metal forms both an oxide and 
an acid, they generally exist in combination ; as examples of this 
may be cited the chromate of chromium, tungstate of tungstenum, 
stannate of tin, &c. &c. Minium is then also arranged in this series 
of compounds.—J6id. 
ON AMMONIA-AMIDIDE OF HYDROGEN. BY PROF. DANIELL. 
Professor Daniell observes, that ‘‘ if we add to a cold solution of 
bichloride of mercury a very slight excess of ammonia, a copious 
white precipitate is formed, and the liquid is found to contain exactly 
half the chlorine of the bichloride combined with hydrogen and 
ammonia as muriate of ammonia. The white powder, which has 
long been known by the name of white precipitate of mercury, con- 
tains all the mercury and the remaining half of the chlorine. Dr. 
Kane believes that it is a compound of chloride and amidide of mer- 
cury, and that its formula, adopting 202, the ordinary number for 
mercury, is Hg Cl,4+2N Hy. 
«« An amidide of mercury has, however, never been obtained in a 
separate state. 
“‘ When potassium is heated in dry ammoniacal gas, hydrogen is 
set free, and a.compound is formed, which is a fusible solid of an 
olive-green colour, which has been supposed to be an amidide of 
potassium, or Ka, NH,, but it likewise contains undecomposed 
ammonia. It has, however, been observed, that if ammonia were 
simply reduced to the state of amidogen in this process, 4 volumes 
should be decomposed and evolve 2 volumes of hydrogen, but in the 
numerous experiments of Gay-Lussac and Thenard, never more than 
35 volumes were required to furnish 2 volumes of hydrogen, so that 
the constitution of the green substance must be considered as very 
problematical. 
“Such is the evidence upon which we are required to review all 
the compounds into which ammonia enters with reference to this 
new radical, which has never been isolated or transferred, and to con- 
sider ammonia itself as an amidide of hydrogen, or N H.+H. 
«« Ammonium, which we have considered as the radicle of the 
common salts of ammonia (an hypothesis which we have found to be 
so remarkably confirmed; by the results of electrolysis), is then a 
subamidide of hydrogen, or N H, + H,; and sulphate of ammonia 
NH,+H,+0+5 O,, or a sulphate of the subamidide of hydrogen ; 
and oxalate of ammonia, NH,+ H, +O+C, O;, an oxalate of the 
oxide of subamidide of hydrogen, and so on with the salts of the 
other acids. 
«« An immense amount of ingenuity has been expended upon this 
hypothesis, but, as the nature of chemical analysis has been most 
