PROCEEDINGS OF THE SUMMER MEETING. 29 



the precipitate, with the lead salt, the same as we do with the zinc salt. 

 We may form a very beautiful precipitate of this class by using some 

 other material, as for example, with this nitrate of silver, when we 

 get the beautiful canary-colored precipitate. It will answer very 

 nicely for an insecticide, but costs about a dollar per ounce and so is 

 objectionable on that account. Finally, we have this waste product, 

 London purple, a waste product formed in the manufacture of 

 aniline dj^es. They attempted to throw it away on land and then 

 tried to pour it into the rivers, but it poisoned the land and killed 

 the fish in the rivers and the government forbade its being deposited 

 anywhere except in deep sea water. They couldn't dispose of it 

 except at a large expense. They found it could be used for Paris green, 

 and it is now largely exported and used in this country for a poison. We 

 may use any of these compounds of arsenic if we have the arsenic in 

 such form as to make it safe, and not injure the plant. If we have it in 

 the form of arsenite of soda the soluble arsenic is injurious to the plant. 

 We must have it in some form in which the material is entirely insoluble. 

 We may have it in the form of Paris green or of Scheele's green, or in the 

 form of arsenite of lead, but we must get it in such form as to make it as 

 cheap as possible, and for this purpose we can get it in the form of 

 arsenite of lime, which is entirely insoluble. 



I have a litle of the arsenite of lime formed here. The question is, does 

 all of the arsenic remain insoluble and not injurious to the plant? We 

 have a very delicate test for the presence of arsenic made by sulphuretted 

 hydrogen. I have a quantity of the arsenic dissolved by boiling it in 

 water. I will take a little of this solution and see if we detect the pres- 

 ence of arsenic by this test. The sulphuretted hydrogen detects the arse- 

 nic by forming the yellow sulphite of arsenic. We will see whether 

 this arsenite of lime contains any of the arsenic in solution, because, if 

 the arsenic is in solution, it will kill the trees as well as the fungi. You 

 see there is no precipitate, showing there is less than one part in a 

 million because no precipitate is formed. Here is the arsenic, or "white 

 arsenic" of the slio}>s, a very cheap material. I have bought it for fifteen 

 cents per pound. It can be bought for ten cents. One ounce and a half 

 of this will form a spraying mixture of forty gallons when formed into 

 the arsenite of lime. Take an ounce and a half of this arsenic and brini; 

 it into solution. It dissolves very slowly, for here is some that I boiled a 

 considerable time, in water, and you see that most of it remains insol- 

 uble. It takes a very large amount of water to bring it into solution. 

 But it readily dissolves in an alkaline solution. Take an ounce and a half 

 of this arsenic and four of sal-soda and put the whole into water and boil 

 it, and you get the whole into solution very easily. Now take this arsen- 

 ite of soda and bring it into contact with slaked lime, which is a very 

 cheap material. For less than two and a half cents you can get a spray- 

 ing mixture which can be very readily used by anybody and very easily 

 prepared and you get for less than two and a half cents forty gallons of 

 spraying mixture. It is both an insecticide and fungicide. As a spray- 

 ing mixture this material is very effective. So far as a germicide is con- 

 cerned, the arsenite of lime combined with Bordeaux mixture may be 

 used. If you add that to the Bordeaux you will get a little of Scheele's 

 green. It does not need to be combined with Bordeaux mixture. If you 



