MONTANA EXPERIMENT STATION. 265 



ir'.ne the exact amount of cyanide necessary to h -.-n-.c^Mtc a room, car, 

 ship or building or any kind the cubic contents must be accurately 

 computed. As an example : a room 20 x 30 x 10 feet contains 6,000 

 cubic feet of air space. To estimate the amount of cyanide ncessary 

 for this inclosure multiply 6,000 by 0.25 ; thus: 6,000 times 0.25 equals 

 1500 grams. To reduce this to ounces divide by 28.35 ^s there are 

 ^8.35 grams in an ounce; thus: 1500 divided by 28.35 equals 53 

 ounces, the exact amount necessary for the inclosure. It is now 

 easy to determine the amount of acid and water, as a half more acid, 

 liquid measure, than cyanide, and a half more water than cyanide 

 are used ; thus : 53 divided by 2 equals 26.5, which added to 53 

 equals 79.5 ounces of acid or practically 5 pounds liquid measure. 

 Again 79.5 or practically 80, as we usually discard fractions, equals 

 40, which added to 80 makes 120 ounces of water." 



In liberating the acid the gas is first measured and poured into 

 an earthenware dish, then the ^j-ater is measured and poured into the 

 acici The potassium cyanide which has been previously weighed is 

 then added to the acid and water after every precautionary arange- 

 ment has been made. If a room is to be fumigated, a bag contain- 

 ing the potassium cyanide should be suspended directly above the 

 jar with the string suspending it passing through a pulley. Then 

 the operator from the door may release the string and allow the bag 

 to settle into the jar. If the space to be fumigated is under a tent 

 the cyanide may be dropped in from the hand. Close the door tight- 

 ly or drop the tent quickly and leave the desired length of time. The 

 room or the tent should be air-tight. The exposure usually employ- 

 ed is thirty to forty minutes. 



Some horticulturists fumigate their green-houses a few times a 

 year and are able b\ this means to keep down all injurious insects 

 except the red spider. In fumigating mills, hotels, etc., it is neces- 

 sary to have an arrangement for ventilating the rooms from the out- 

 side. This may be done by attaching cords to the window sashes. 

 After furriigation, such buildings must be allowed to ventilate thor- 

 oughly before entering them. In fumigating buildings give an ex- 

 posure of I hour to 24 hours. 



Bordeaux Mixture. 

 We quote the following from Farmers' Bulletin, No. 38, U. S. 

 Department of Agriculture, prepared by Dr. Galloway: 



"All things considered, it is believed that the best results will 

 be obtained from the use of what is known as the 50-gallon formula 

 of this preparation. This contains: 



Water . .' 50 gallons. 



Copper sulphate 6 pounds. 



Unslacked lime 4 pounds. 



