and the Constituents of Well- and River-waters. 209 
first portion of water which distilled over was strongly alka- 
line, the potash added having retained the nitrous acid and libe- 
rated the ammonia. The water as it distilled became less and 
less alkaline ; and after two gallons had passed over, the water 
ceased to alter the colour of the most delicate red litmus-paper, 
being perfectly neutral. Six experiments with lead, similar to 
the preceding, were made with this neutral water, and in neither 
instance was the lead acted upon, nor was a trace of lead to be 
found in solution. 
Having proved, by the preceding experiments, that the solvent 
action of distilled water upon lead is due entirely to the presence 
of nitrous acid, either free or combined with ammonia, and that 
water deprived of this acid has no action upon lead, as this ap- 
peared to afford a key to the difficult question regarding the 
solvent action of waters on lead in general, I instituted a number 
of additional experiments. 
Nitrous acid, as is well known, forms four different combina- 
tions with oxide of lead :— 
Neutral monobasic nitrite . . PbO, NO# 
Hibasic mitre 2 PP el SP ho NO? 
Tribasic nitrite (Bromeis) . . 3PbO, NO? 
- Quadribasic nitrite . . . . 4PbO, NO®%. 
If, through a solution of either of the basic nitrites of lead, a 
current of carbonic acid be passed, the basic atoms of oxide are 
precipitated as carbonate, and neutral nitrite of lead, PbO, NO%, 
remains in solution, e. g. 
4PbO, NO? + 8C0?=3(PbO, CO?) + PbO, NO®. 
If this neutral nitrite of lead be placed in contact with more 
metallic lead and allowed to remain, the solution acquires in a 
few minutes an alkaline reaction from the formation of a qua- 
dribasic salt and production of ammonia. This remarkable 
change is expressed in the following equation :— 
3(PbO, NO) + 3HO + 6Pb=2(4PbO, NO®) + PbO + NH3*. 
The quadribasic nitrite, by exposure to the atmosphere, is decom- 
posed by carbonic acid, the three atoms of basic oxide combine 
with this acid and are precipitated as carbonate, neutral nitrite 
being left in solution, which again in contact with more lead 
forms another atom of ammonia, and is converted itself mto the 
quadribasic salt. Thus a very minute quantity of nitrous acid 
* Tf a solution of neutral nitrite of lead be boiled with metallic lead, a 
quantity of ammonia is obtained which corresponds with the above equa- 
tion. The experimental results will be communicated in a subsequent 
paper. 
Phil. Mag. 8. 4. Vol. 14. No. 92. Sept. 1857. r 
