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percentage, it is still believed that twenty-four hours should be the 
minimum time. 
[N’ow let us see what practical bearing these results may have upon 
quarantine practice. The regulations require for the holds of vessels, 
either iron or wood, 10 per cent volume of gas, and forty-eight to 
seventy-two hours’ exposure in the case of wooden vessels ; twenty- four 
to forty-eight hours in the case of iron vesseJs. This percentage of gas 
can only be obtained by the use of special apparatus in the nature of a 
specially constructed furnace and a fan or blower driven by an engine 
to aspirate the gas from the furnace as fast as formed and introduce it 
into the hold of a ship undergoing disinfection. Investigation of many 
quarantine stations has demonstrated that in none of them was 10 per 
cent sulphur dioxide used. In many of them the percentage ranged 
from 2.50 to 6 per cent. So far as the record shows there is no instance 
of a sliip once having undergone disinfection at a national or State 
quarantine station having imparted the infection of the disease which 
was principally the subject of quarantine, yellow fever, to any person 
or to any community subsequently in contact therewith. 
I It would seem that as a result of these experiments there might be an 
essential change made in the quarantine regulations upon this point. 
Five per cent sulphur dioxide intelligently applied for twenty four hours 
would seem to be all that would be necessary. This percentage of gas, 
or very near it, can be obtained by the old method of the combustion 
of sulphur in pots which can be placed in the holds or other apartments 
of ships which it is desired to disinfect. And the time can be shortened 
from seventy-two hours as a maximum to probably twenty-four hours 
as a maximum instead of a minimum, in all cases. 
The above experiments having served to show the minimum percent- 
age of gas necessary to effect certain disinfecting results and the mini- 
mum time necessary to arrive at these same facts, it would now be well 
to consider the means for the practical application of sulphur dioxide 
as a disinfecting agent. 
I Several methods may be employed. Let us commence with the pre- 
‘sumption that we desire to obtain a 5 per cent atmosphere in a given 
space. How can this be arrived atf As has been mentioned heretofore, 
there are numerous methods, the burning of sulphur, the production of 
sulphur dioxide by the action of sulphuric acid upon either copper or 
sulphur, and it has also been noted that under the influence of pressure 
j or low temperatures, or the two combined, sulphur dioxide may be 
reduced to a liquid condition readily expansible by the application of 
heat. Therefore, the first method may be given as the use of liquefied 
sulphur dioxide in such quantities as to obtain the percentage required. 
f It must be borne in mind here (having reference to the atomic weights 
of sulphur, oxygen and sulphur dioxide) that 1 pound of sulphur will pro- 
duce 2 pounds of sulphur dioxide. Tlierefore, reversing the proposition, 
2 pounds of liquefied sulphur dioxide must be used in lieu of 1 pound of 
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