376 On definite Proportions» 
arsenite being prepared by the solution of white arsenic in 
carbonate of potass, until the solution, when cooled, de- 
posited arsenious acid in crystals. The precipitate, which 
was at first viscid, became a powder when heated, and was 
completely deposited. It was placed ona filter, washed, 
and well dried ; it then weighed 39'126 gr, When melien 
in a red heat in a small glass retort, it aitorded -665 er. of 
water, and 1°651 of arsenious acid. Consequently 20 gr. 
of the protoxide of lead had afforded 36°81 gr. of neutral 
arsenite. The same experiment was then performed ina 
different manner. I carefully mixed 5 gr. of protoxide of 
lead with 6 of arsenious acid, and heated them together in 
a covered crucible of platina, i increasing the heat s! slowly to 
complete ignition. ‘The arsenite thus obtained weighed 
9°22 gr. 
Now if 36°81 parts of this arsenite contain 20 of the 
protoxide of lead, the salt is thus constituted : 
Arsenious acid... 45°667 100:000 
Protoxide of lead 54°333 118'977 
If however we calculate from the last experiment, 100 
parts of the acid must be saturated by 118:476 of the prot- 
oxide; so that the experiments differ very little from each 
other. 
The arsenite of the protoxide of lead being a substance 
but little known, I think it right to make some remarks on 
its external characters. If it has been prepared by precipi- 
tation, the white powdery salt is perhaps the most strongly 
electrical of all known bodies. When I rubbed a little of 
it in a mortar, it cracked and flew about; and when I en- 
deavoured to pour it out, it remained adhering to the mor- 
tar: upon detaching it from the mortar, it spread, in falling, 
- over a surface several inches in diameter. Sulpbur exbibits 
similar appearances, but in a much less considerable degree. 
The salt when fused is not very fluid; it is transparent, 
and retains this property when cold: its colour is very 
slightly yellow; and if the lead contains a trace of copper, 
it becomes of a bottle green; but if made from common 
litharge, it is quite black. If it is heated with access of 
air, some arsenious acid is disenaged, and some arscniate of 
the protoxide is formed, which sinks in the salt when it is 
fused. 
The composition of the arsenious acid may easily he cal- 
culated from that of the arscnite of the protoxide of lead, 
But my first conjecture, that it contained, like the sul- 
phurous acid, twice as much oxygen as the ‘base that. it sa- 
turated, is not confirmed by the investigation, For since 
118°977 
