157 
The number of cubic feet in the house should first be accurately 
calculated. The method of doing this may be illustrated by a sim- 
ple computation based on the dimensions given in the accompanying 
figure, the understanding being that the length of the greenhouse 
is I GO feet. (Fig. 42.) The cubic contents of the rectangular sec- 
tion of the house, a c d e, equals 24X6X ioo=i4>400 cubic feet; 
that of the triangular section a b x, equals 8X^X100-^-2=3,200 
cubic feet ; and that of the other triangular section, b c x, equals 
8X i^X ioo-r-2=6,400 cubic feet. The cubic contents of this house 
are, therefore, 14,400 -{-35200-1-6,400=24,000 cubic feet. Assum- 
ing this house to be of no more than the average tightness, we may 
safely use potassium cyanide at the rate of one ounce to every 3,000 
cubic feet of space, and 24,000 divided by 3,000 gives 8 as the num- 
ber of ounces required in this illustrative case. 
The next procedure is to prepare the materials for use and to 
place the jars in the house. For every ounce of the potassium cya- 
nide used, two ounces of sulphuric acid and four ounces of water are 
required. Two o«nces of the cyanide is about the right quantity for 
each jar, therefore, for a house of the above dimensions, four jars 
should be placed at equal intervals along the aisles, and the eight 
ounces of cyanide divided into four equal parts, and each part put 
into one of the paper bags. These are used not only for convenience 
in handling the cyanide when placing it in the jars, but also because 
they slightly delay the action of the sulphuric acid upon it, thus giv- 
ing the fumigator ample time to leave the house before the reaction 
occurs. The jars being in place and the cyanide properly weighed 
and bagged, the next step is to close all the ventilators in order to 
prevent any avoidable escape of gas. The water — four liquid ounces 
to every avoirdupois ounce of cyanide — is then placed in each jar, 
the sulphuric acid — half as much as the water — is added, and as 
soon after as possible the bags of cyanide should be put into the jars 
and the house vacated immediately. Doors should be locked and 
labels posted indicating the danger. No one should enter the house 
until it has been thoroly aired by opening the side doors, and, if con- 
venient, the ventilators also. It is best to fumigate in the evening, 
keeping the house closed till morning. I have never found a green- 
house so tight that the fumes would remain in it in dangerous quan- 
tities all night; nevertheless, it is safest to air the house well before 
entering. 
Precautions and Miscellaneous Directions. — As cyanide of potas- 
sium is a powerful poison it should be handled as little as possible. 
It should be kept in tightly closed cans or jars, plainly labeled, where 
it will be inaccessible to persons not acquainted with its poisonous 
properties. Use only a grade 98 to 99 percent pure. It may be ob- 
tained in either granulated or lump form, the former being the most 
convenient for use in fumigation. 
