15 
SULPHUK DIOXID. 
In order to compare the merits of formaldehyd with sulphur dioxid 
gas in disinfection against mosquitoes, similar experiments were made 
by burning sulphur and with the liquid sulphur dioxid gas. 
The power of sulphur dioxid to destroy all forms of animal life is 
well known. On account of its destructive action upon fabrics and 
metals, this agent is of little practical use in the disinfection of dwelling 
houses, cabins of ships, and similar places. This destructive action is 
due to the moisture which combines with the sulphur dioxid to form 
sulphurous acid, which is the real disinfecting agent. Dry sulphur 
dioxid has practically no effect upon bacteria. Our work has shown 
that very small atmospheres of the dry gas will quickly destroy mos- 
quitoes, and we therefore believe that the destruction of these insects 
may be accomplished in dwelling houses with little danger of injuring 
fabrics or tarnishing metals. Sulphur dioxid is so far superior to for- 
maldehyd as an insecticide that even this risk should not outweigh the 
certainty of its action. The gas may now be obtained in its liquefied 
form, either in tin cans, in syphons, or in iron cylinders, affording very 
convenient methods of quickly introducing a given amount of the dry 
gas into an inclosure. 
Xo. 11. 
Two pounds of sulphur were burned in a small room with a capacity 
of exactly 500 cubic feet. This gives nearly the prescribed 4 per cent 
of gas. The room was specially built for experiments with gaseous 
disinfectants and is made very nearly air-tight. The time of exposure 
was four hours. 
The sulphur was in the form of “flowers.’’ It was burned in a small 
l>ot and the fire started with alcohol. 
Mosquitoes were exposed in the small pill boxes with gauze lids, as 
follows : 
In pill boxes — 
Under 1 layer toweling 
Under 2 layers toweling 
Under 4 layers toweling 
Wrapped twice in towel 
Covered with 1 sheet newspaper 
In corner folded newspaper 
In inside pocket of overcoat 
On wall back of coat 
On wall back of 3 towels 
On floor under several loose towels 
In battery jar one-third full crumpled toweling 
Dead. Alive. 
4 0 
7 0 
4 0 
3 0 
5 0 
5 0 
3 0 
4 0 
4 0 
4 0 
12 0 
No bacteria were exposed in this test. The result showed that the 
prescribed amount of sulphur will kill the insects in a much shorter 
time than is required to destroy bacterial infection, and that the sulphur 
dioxid possesses considerable penetrating power in this short time. 
