10 



This makes constant stirring necessary. Paris green does not dissolve in 

 water, and is merely mixed witli water to facilitate its even distribution on 

 vegetation in the very small quantities that are necessary to destroy insects. 

 The finer the jioison is ground, the quicker its effect on the insects which eat 

 it, because the minute crystals are more rapidly dissolved by the digestive 

 juices in the stomachs of the insects. The finer it is ground, the better also 

 it will remain suspended in a liquid application. For most insects, one ounce 

 of Paris green in 10 gallons of water is the standard strength ; but some plants 

 with coarse foliage, such as the potato, will stand double that strength. 



Adulteration of Paris Green. — The unsatisfactory results so frequently 

 rejiorted from the use of Paris green against cutworms and other pests is 

 largely due to the frequent adulteration of this article. The following are 

 some of the methods by which pure Paris green may be known: 



It dissolves wholly and freely in ammonia, forming a beautiful blue liquid. 

 All of the material which fails to dissolve rei)resents so mucli crude matter 

 which has been added as an adulterant. AYhile this affords valid grounds for 

 rejection of the article, it must be borne in mind that white arsenic and a 

 luimber of other sul)stances used in the adulteration of Paris green are also 

 soluble in ammonia, hence the test is but a partial one. 



Another test of purity is to talvC a small (juantity of the green upon ;\ slip 

 of glass, holding it at such an angle as will cause it to slide. If it is pure it will 

 leave a bright green streak on the glass; if adulterated, this streak would be 

 pale in colour witli light and darlcer shadings, due to the presence of such 

 articles as arsenic, gjTsum, flour and other foreign sulistauces which the 

 intense green hides from view, unless critical examination is made with a com- 

 Ijouud microscope, which will show the ParLs green to consist entirely of green 

 spheres. In case of adulteration, the green spheres are mixed with matter 

 more or less white, of crystalline irregular shape, entirely foreign to the pure 

 article and should be rejected, as likewise should all samples showing any 

 tendency to dampness or caking. 



Arsenate of Lead. — A poi.son which has come into much notice since the 

 work of the Massachusetts Gypsy Moth Commission is Arsenate of Lead, which 

 has been jilaced on the market in a very convenient form under the name of 

 Bowker's Disparene and Swift's Arsenate of Lead. The chief advantages of 

 Arsenate of Lead are that it can be applied to all kinds of foliage with less 

 danger of injury than is the case with Paris green : and. on account of its 

 fine state of division, it lasts longer on the foliage, because it does not wash 

 off so easily. The cost of using it is about the same as that of Paris green. 

 becau.se, although cheaper, jjound for pound, it is necessary to use three times 

 the amount of it to get the same results. Arsenate of Lead may he made at 

 home. Formul;e for its preparation vary slightly; but in the T'nited States 

 Division of Entomology, Bulletin Xo. 41, the following instructions are given 

 for making the Arsenate of Lead wash ready for use: — 



Arsenate of soda 10 ounces. 



Acetate of lead m 



Water 1 ."0 to 200 gallons. 



