270 m. ledoyen's disinfecting fluid. 
founded on the premises, that hydrosulphuric acid is the 
cause of contagion and foetor, in the miasm and exhalations 
from decomposing animal matter, the truth of which is by 
no means perfectly established, else, as Mr. Bell observes, 
why do not the occupants of our laboratories become dis- 
eased through its influence. Admitting that sulphuretted 
hydrogen is the noxious agent to a certain extent, the ques- 
tion arises, are these salts efficient in decomposing and neu- 
tralising its effects ? 
Chloride of Zinc. 
If neutral chloride of zinc be 
treated with sulphuretted hy- 
drogen, but a small part of the 
salt, will undergo decomposi- 
tion forming sulphuret of zinc 
and hydro-chloric acid. 
The presence of free acid in 
solutions of zinc salts, prevents 
their decomposition by the gas, 
and hence the disinfecting ac- 
tion of the solution is destroy- 
ed. 
Nitrate of Lead. 
If nitrate of lead be treated 
with hydrosulphuric acid, sul- 
phuret of lead will be formed 
and nitric acid and water be set 
free. 
As the salts of lead are de- 
composed by the gas in ques- 
tion, in the presence of free 
acid, the disinfecting action 
will not cease till all the salt 
has been decomposed 
The'conclusicm arrived at is that chloride of zinc has very 
decided powers as an anti-septic — whilst nitrate of lead is 
far more efficient as a destroyer of noxious effluvia contain- 
ing sulphur. 
In reference to Ledoyen's solution, the discoverers speak 
of its powers in the following terms : 
1st. "It disinfects night soil, not destroying but increasing 
vegetation, more particularly as regards agriculture ; com- 
pletely preventing the disease in potatoes, when the land 
is manured with disinfected night soil." 
2d. " It disinfects hospital wards of miasma, also cellars, 
water closets, and buildings infected by impure gases." 
3d. " It disinfects sailors suffering from fever on board 
