264 MONTANA EXPERIMENT STATION. 



are not prepared to say that there is not some benefit to be derived 

 from the presence of the salt and the excess of lime and for the pre- 

 sent we recommend the formulae given below. We suggest, how- 

 ever, that fruit-growers make more careful tests of the wash with 

 the salt omitted and with the sulphur and lime in the proportion of 

 I to I. It will, of course, be understood that a variation in the 

 amount of wafer used in the formulae will result in making the wash 

 more or less concentrated according as more or less water is used. 



The ingredients may be used in the following proportion : 



Lime i pound. 



» Sulphur I pound. 



Salt Yz to 1 pound. 



> Water 4 gallons. 



While we recommend the addition of salt under ordinary cir- 

 cumstances, this substance is unnecessary in the treatment of pear- 

 leaf blister mite, moreover, Prof. Piper found it to be unnecessary 

 in treating for the San Jose scale. 



Slake the lime thoroughly in a vessel, which is to be used in 

 boiling the mixture, then add the sulphur; boil at least for one hour 

 vising enough water to completely cover the sulphur and lime. Add 

 the remainder of the water of the formula. 



Hyhrocyanic Acid Gas. 



This very deadly gas is coming into common use as a means of 

 destroying many foims of insect life that cannot be controlled with 

 poisons or contact insecticides. 



The gas is a deadly poison to all animal life and in its use great 

 care must be taken not to inhale it. It is prepared by the action of 

 sulphuric acid and potassium cyanide. The potassium cyanide, 

 again, is a deadly poison and a small quantity taken into the stom- 

 ach will result in death. Potassium cyanide may be obtained from 

 Roesler Hasslacher & Co. of New York City. 



The gas is used in different strengths for dift'erent purposes. 

 The desired strength being obtained by taking a given quantity of 

 the potassium cyanide and adding to it the required amount of sul- 

 phuric acid. For fumigation of nursery stock the proprtions used, 

 per each cubic foot of space inclosed are: 



Potassium cyanide, 0.25 grams. 



Sulphuric acid, 98 per cent. 



One-half more acid, liquid measure than cyanide. 



Water, one-half more water liquid measure than acid. 



The following is taken from Johnson's Fumigation methods: 



"The amount of cyanide necessary for any inclosure is dt^termin- 

 ed in terms of grams per cubic foot of space inclosed To deter- 



