198 OHIO EXPERIMENT STATION: BULLETIN 332 



Paste arsenate of lead. — Arsenate of lead in the paste form is 

 white or very light gray in color, and depending upon the water 

 content varies from a thin paste to a material of puttylike con- 

 sistency. The thinner forms mix readily with water, but the drier 

 forms are sometimes mixed with considerable difficulty, and in such 

 cases the operation may be facilitated greatly by the use of an 

 arsenate of lead mixer, as shown in Plate XIV, Fig. 3. 



After the container has been opened and a part of the lead 

 used, the top should be closed tightly to prevent the remainder from 

 drying out. Likewise lead carried over the winter should not be 

 permitted to freeze, since this too will dry it out. The dried or 

 frozen lead, while still retaining its poisonous properties, is much 

 more difficult to dissolve for use and at the same time is much less 

 likely to remain well in suspension after it is dissolved. The addi- 

 tion of dissolved soap, at the rate of 1 or 2 pounds to 50 gallons of 

 spray, has a tendency to correct this fault and also adds somewhat 

 to the adhesive and spreading properties of the mixture. 



For most insects arsenate of lead in the paste form is used at 

 the rate of 3 pounds to 50 gallons of water, but for controlling some 

 of the more hardy pests, such as elm-leaf beetle, gipsy and brown- 

 tail moths, it should be used stronger — from 4 to 6 pounds to 50 

 gallons of water. 



The dry or powdered form of arsenate of lead. — The dry form 

 of this poison is of comparatively recent origin and seems to have 

 been devised by manufacturers for three reasons : To create a new 

 selling point; to minimize shipping expense by eliminating the ex- 

 cess of water, and to obviate the danger of drying out or freezing. 

 The only item of superiority of great practical value from the con- 

 sumers' standpoint is the last named, and this is counterbalanced 

 by the fact that some of the dry forms are decidedly inferior in so 

 far as their property of remaining in suspension is concerned. At 

 the same time, in some instances the cost per gallon of diluted spray 

 is considerably greater than that of a solution of equal strength 

 prepared from the paste lead. 



It is customary to use one-half the amount of lead in the pow- 

 dered form that is used in the paste; thus, II/2 pounds is used to 

 each 50 gallons for ordinary insect control, but for the more resist- 

 ant forms as much as 3 pounds may be used. Little difficulty is 

 experienced in dissolving the powdered lead for use. 



When all points are considered, the writer has a slight prefer- 

 ence for the paste form, but if the powdered form can be had at 

 comparable prices and is found by test to equal the paste in other 



